Anatomy and Physiology
In origin and early development the ovary and testis are identical. The gonad and mesonephros or primitive kidney are developed from the urogenital fold. The gonad first forms as a medio-ventral thickening of the fold, which gradually expands until it becomes attached by a mere stalk. At first, the gland is made up merely of a superficial epithelial layer, and an inner epithelial mass, or epithelial nucleus. In the process of development, large primordial germ cells migrate from the entoderm of the future intestinal canal, and pass through the stalk to the gonad. In the case of the male gonad, seminiferous tubules are very difficult to make out in embryos smaller than 24 millimeters. Then they suddenly differentiate out as solid cords of germ cells, while the connective tissue grows in around them. These connective tissue sheaths unite at the center of the organ to form the anlage of the mediastinum testis. The testicular tubules unite and converge toward the hilus, there to meet the anlage of the rete. At the mesonephric end of the testis, the rete first appears as a collection of cells, differentiating out from the inner epithelial mass of the gonad. These cells gradually grow out to meet the collecting portions of the mesonephric tubules on the one hand, and the seminiferous tubules on the other. The rete is represented as cords of cells at first, which in forty millimeter embryos hollow out to form tubules.
The mesonephros, or primitive kidney, early starts to degenerate cranio-caudally,—the tubules becoming separated into a cranial and caudal group. The collecting and secretory parts of the cranial group separate, the collecting tubules growing out to meet the rete with which they unite to form the efferent ductules of the epididymis. The caudal group of tubules is vestigial and becomes the paradidymis. The mesonephric duct becomes the vas deferens, connecting as it does with the tubules of the epididymis, and emptying into the urethra at Müller’s tubercle or, as it later becomes, the colliculus seminalis.
The seminal vesicles arise as hollow saccules from the dorsal wall of the mesonephric duct just as it empties into the urethra. The prostate develops as an outgrowth of the dorsal urethra just posterior to Müller’s tubercle. The bulbo-urethral glands appear as solid, paired, epithelial outgrowths from the entoderm of the urogenital sinus.
Müller’s duct, at first a solid tube growing from the anterior part of the mesonephros, and ending at Müller’s tubercle, becomes a hollow tube, and in the female forms the entire genital tract except for the gonad and the lower part of the vagina. In the male, the anterior part remains as the vestigial appendix testis, and the posterior part, as the vagina masculina. Ellenberger states, however, that this embryonic structure is very seldom seen in the mature bull.
The Male Reproductive Organs include the penis and testes, together with the excretory passages which connect the testes with the urethral canal. These excretory ducts include the epididymis, vas deferens, and seminal vesicles. Posterior to their termination in the urethra, there are connected the ducts of the prostate gland and the bulbo-urethral or Cowper’s glands.
Testes: The testicles of the bull are relatively large. Varying with the size and age of the animal they measure from fourteen to seventeen centimeters in length, including the epididymis, and from six to eight centimeters in diameter. Each testicle is enclosed within a serous sac, the tunica vaginalis, whose visceral layer is very intimately fused with the underlying covering of the organ, the tunica albuginea. The tunica albuginea is quite thin and consists of connective tissue which is rich in elastic fibres. Muscular tissue is not present as it is in the case of many mammals. Inside the tunica, and closely attached to, though separated from, the parenchyma by a thin layer of connective tissue, is a layer of very loose connective tissue, which because of its rich supply of blood vessels is termed the tunica vasculosa. The parenchyma is of a yellowish gray color, and of a rather soft consistency. It is made up of the seminiferous tubules, rete, and the connective tissue stroma, the mediastinum testis. On section, the mediastinum appears as the center or axis of the entire organ. It is star-shaped, and radiates connective tissue septa out into the parenchyma to support and separate the tubules. Ellenberger states that the testis of the bull and all ruminants lacks a closed system of interlobular septa, because of the feeble development of the connective tissue.
The principal blood vessels and rete tubules are found in this structure, the function of the latter being to connect the seminiferous tubules and the efferent tubules of the epididymis. The epithelium of the rete is quite irregular,—consisting in places of a single layer; in others, of two layers. At some points there are formed groups of several cells lying over one another, with swollen homogeneous basal cells, which sometimes form projections into the lumen.
The interstitial tissue, besides conveying the blood vessels to the organ, contains many “interstitial cells.” These cells are relatively sparse in the adult bull, and are comparatively delicate, slightly granular, often shuttle-shaped, with a rather small nucleus. Embryologically they are derived from a syncitium arising from the mesothelium of the genital ridge, differentiating out by growth of the cytoplasm. They contain large quantities of fat, and elaborate the internal secretion of the testis. This secretion governs the development of the secondary sexual characters, and has a profound influence on the general body metabolism, and development of the skeleton. The interstitial cells appear early in embryonic life even before there is any differentiation of sex, and their greater relative development in the fetus is indicative of a future male development. In very young embryos, the growth is very rapid, followed, however, by a period of atrophy, during which the seminiferous tubules undergo marked development. Pende (21) states: “There seems to be an inverse relation between the growth of the tubular and interstitial tissues, as one is hypoplastic when the other is in full activity.” From birth to the onset of sexual maturity, which may be called a period of rest for the testicle, the cells are few in number. With the accentuation of the secondary sexual characters, and the beginning of sexual life, these cells again increase in number and activity.
The parenchyma of the testis consists for the most part of the seminiferous tubules, which, on account of the courses they take in the different regions, are divided into groups. The peripheral tubules are the much-contorted tubuli contorti. These anastomose to form the much shorter tubuli recti. These in turn anastomose frequently, uniting to form the rete testis. The rete proceeds through the mediastinum to form the efferent ductules which break through the tunica albuginea to form the greater part of the head of the epididymis. The tubuli contorti are the longer and more numerous of the tubules, for it is here that practically all the spermatozoa are produced. The straight tubules are relatively so short that they may be regarded more in the light of the beginning of the system of excretory ducts.
The seminiferous tubules consist of a thin peripheral membrana propria upon which rests the seminal epithelium, which is made up of the essential semen forming cells, and the cells of Sertoli. The spermatogenic cells may be divided into three groups, from within outward: the peripheral single layer of small cuboidal spermatogonia; one or two rows of large spermatocytes; and three to five rows of spheroidal spermatids. The cells of Sertoli are more or less of the syncitial type,—large in size and irregular in outline. They occur at various intervals between the layers of spermatogenic cells, with their bases resting upon the membrana propria. Centrally they send out protoplasmic processes for variable distances,—some even reaching the border of the innermost cell layers.
Spermatogenesis: In this process, the primary germinal cells, the spermatogonia, divide to form the primary spermatocytes. Maturation consists of two cell divisions of the primary spermatocytes, and these in turn form four spermatids. During the process, the number of chromosomes is reduced to half the number characteristic of the species. The spermatids then become converted into mature spermatozoa. This mode of transformation may be seen in Plate I. In the process, the nucleus of the spermatid forms a large part of the head: the centrosome divides, part passing to the extremities of the neck. One centrosome becomes the anterior, and remains attached to the head, while the other divides to form the posterior centrosome. The latter is divided into the anterior part, and the posterior nodule or annular ring. Besides this, the posterior centrosome becomes elongated to form the axial filament, and the cytoplasm forms the sheaths of the neck and tail. The spiral filament of the connecting piece is derived from the cytoplasmic mitochondria. At this time, a large part of the cellular cytoplasm is cast off. Meanwhile, the spermatozoa sink their heads into the long protoplasmic processes of the Sertoli or “nurse” cells which furnish nutritive material for their complete development. Finally the adult cells are cast off into the lumen. The structure of the spermatozoa, and a discussion of the semen will be taken up later.
Epididymis: The epididymis is divided into three parts: the head, body and tail. The head is made up principally of the lobules formed by the much-coiled efferent ductules proceeding from the rete. The ductules, about twelve in number in the bull, unite to form the body, which remains coiled and runs along the postero-medial part of the testicle to which it is more or less closely attached. To quote Ellenberger (23): “The transition from the rete into the ductules is gradual, as the characteristic epithelium of the latter (ductules) begins in cavities without walls, and at first, gradually form a wall which is well marked out as a thin ring of interstitial tissue.... The epithelium of the ductules is in sharp contrast to the rete in that it has a single-layered ciliated columnar epithelium, in which here and there one finds round basal cells. The dark and light columnar cells alternate; the cilia are often cemented together, and form cone-shaped, homogeneous appearing protuberances. The secretory activity is quite clearly observable. In the light cells one finds secretory globules, accumulating in rows, sometimes above, other times below, arches of cells. The secretory droplets pass from the cells into the lumen, and often lie in irregular layers on the epithelium; also the basal cells appear swollen and shoved out between the cylindrical cells.” At the lower extremity of the testicle, the tail is formed, which is globular in shape, and more or less loosely attached to the testicle. Here the ductules anastomose freely, gradually become less coiled, and end in the single excretory tube, the vas deferens. The epithelium at the tail part is more or less of the pseudo-stratified columnar, ciliated variety. Outside this is a membrana propria, a circular muscular layer, and a connective tissue coat. The secretory activity is very marked here and one finds much secretion in the lumen, Courrier (24), working on the bat, suggests that the glandular activity is conditioned by the secretion from the interstitial (endocrine) gland. The action of the secretion is to dilute the large mass of spermatozoa present, nourish them to some extent and also stimulate them to active motility. Stigler (25) states that the properties of the sperms are modified in the epididymis; the motility, the ability to resist heat, and other properties are augmented, at least in the case of the guinea pig, rat, and mouse. Some authors state that the sperms first become motile when in contact with the prostatic secretion, but I have repeatedly examined the contents of the tail of the epididymis of the bull, rabbit, and guinea pig, finding full motility in each case, though the duration is not nearly as long as when the sperms are ejaculated in the semen.
The Vas Deferens is quite narrow (2 mm.) and runs from the tail of the epididymis to the verumontanum, or colliculus seminalis, where it empties into the urethra in common with the duct of the vesicle. At first it is lined by epithelium similar to that of the vas epididymis, but this changes over into a peculiar low stratified type. Ellenberger describes it as follows: “The epithelium shows a very pronounced basal coat. The overlying cell zone shows more (at the most, three) rows lying over each other of elongated nuclei, while an outline of cell form is not ordinarily noticeable, so that it may be spoken of as a syncitium, and at the same time as a many layered epithelium.” The mucosa forms low, broad folds into the lumen. The tunica propria is a thin connective tissue layer. The submucosa consists of thin connective tissue. Three muscular coats are present: an inner thin longitudinal layer, middle circular layer, and an outer longitudinal layer. All are more or less intimately blended, and are surrounded by the adventitia, made up of connective tissue, elastic fibres and scattered longitudinal muscle cells of the internal cremaster muscle. Near the dorsal surface of the bladder, the ducts come in close apposition, and for ten to twelve centimeters dilate to form the ampullae. Here the mucous membrane becomes much plicated, forming long folds which anastomose freely. The function of the vas is to convey the spermatozoa and secretions from the epididymis to the urethra. Disselhorst (26) believes the ampulla acts as a seminal reservoir and states that he has found spermatozoa stored up in the little pockets in the walls of this structure in animals during the rutting time. He suggests, further, that there is a relation between the state of development of the ampulla and the time occupied by copulation. When the organ is small or absent, as in dogs, cats, and boars, the coition is a slow process, but when the ampulla is large and well developed, as in horses and sheep, the coitus requires a relatively short time. Inasmuch as coitus is so rapid in the bull, and the ampulla is so well developed, it seems as though this function is very probable.
The Seminal Vesicles are very compact glandular structures lying on either side of the median line, on the dorsal side of the bladder, and ventral to the rectum. In the mature bull they measure ten to twelve centimeters in length, four centimeters in width, and about two and one-half to three centimeters in thickness. The glands are distinctly lobulated, quite tortuous, and are often asymmetrical in size and shape. They converge posteriorly, to empty into the urethra at the colliculus seminalis with the ampulla, in a slightly oval slit in the mucosa. Microscopically, the gland is of the anastomosing tubular type, with very poorly developed excretory ducts to the glandular cavities. Posteriorly one finds centrally a few sinus-like narrow excretory passages, which open into the somewhat larger collecting and excretory duct. The epithelium is of the simple columnar type and produces a relatively large amount of secretion. The gland cavities are surrounded by a membrana propria, over which is a relatively thick layer of smooth muscle. Outside this is a connective tissue covering which sends trabeculae or septa in between the lobules. The secretion of the seminal vesicles is a tenacious albuminous fluid with a slightly yellowish tinge, all or part of which appears in the ejaculate in the form of swollen sago-like grains which are soon dissolved following ejaculation and the liquefaction of the semen. The proteid compounds belong to the group of histones. The secretion is liquid when warm and coagulates when cold. Some say that the filling of the vesicles serves to excite sexual feeling, but this is doubtful in view of the fact that in some animals the sexual desire exists before the vesicles are filled. Likewise, Steinach found that rats, whose seminal vesicles had been removed, still retained their desire for copulation. The function of the secretion is to furnish much of the volume to the semen, and in some way it has a distinct bearing on fertility, inasmuch as extirpation of the organs in rats leads to lowered fertility. The vesicles of the bull are in no sense a store-house for spermatozoa, as is usually understood. Repeated examinations in a large number of bulls have led to the finding of spermatozoa there only in very rare instances. That they serve as a resorption place for sperms that are not ejaculated is also very unlikely. Normally, one sees on smear of the vesicles, occasional cells, leucocytes, lecithin granules, sago bodies, and rarely a few degenerated spermatozoa.
The Colliculus Seminalis is a rounded or cone-shaped eminence in the posterior urethra, upon which the ducts of the seminal vesicles and vasa deferentia open. The ducts open separately at the bottom of two narrow slits, one on each side of the mound, there being no distinct ejaculatory duct as in man. The function of the colliculus or verumontanum is not definitely known. It is generally believed that the structure is made up of blood spaces which become engorged during erection, causing a blockage of the posterior urethra, which prevents regurgitation of the semen. Rytina (27), however, demonstrated that the structure is not composed of any unusual number of blood vessels or spaces, and that removal of the organ was not followed by regurgitation of the semen into the bladder during ejaculation. He believes, and quite logically, that its function is to afford a prominence upon which the ducts may empty. The mixture of the thick gelatinous semen with the thin prostatic secretion must occur at the moment of ejaculation and must be perfectly homogeneous, otherwise large numbers of the organisms remain in the thick gelatinous portion of the fluid. The eminence serves this purpose in that the prostatic ducts which converge toward it, may eject their secretion toward the eminence, producing an admixture more evenly and quickly.
Prostate: The bull possesses what Ellenberger calls a diffuse prostate. That is, there is no distinct glandular body as in man. It is composed principally of a glandular sheath around the urethral wall. Just posterior to the neck of the bladder, and in front of the urethral muscle, there is formed a slight dorsal transverse elevation, extending downward on the sides. This is what might be termed the body. The greater part of the gland is “disseminate” in form, being a sheath of glandular tissue embedded in the urethral wall. Dorsally it is about ten to twelve millimeters thick, and ventrally about two millimeters. The gland is a branched tubular structure, the interlobular tissue of which contains much unstriped muscle. The lobules are lined by a columnar type of epithelium. The ducts, about thirty to forty in number, open into the urethra in two rows posterior to the colliculus. The secretion is a thin, slightly turbid fluid, of a faintly alkaline reaction. Its function is to dilute the semen, stimulate the motility of the spermatozoa and nourish them.
Fish (28) believes that the activating property of the secretion is due to enzymes, because boiling deprives the fluid of its power to accelerate the motility of the spermatozoa. Serrlach and Pares, quoted by Marshall (29), working on dogs, have adduced evidence indicating that the prostate is an internal secretory gland which controls the testicular functions, and regulates the process of ejaculation. It is stated that if the prostate is removed, spermatozoa are no longer produced in the testis, and that the secretory activity of the accessory genital glands ceases. These changes, however, can be prevented by the administration of extracts of the prostate. The fact that the prostate elaborates a secretion having a definite relation to the testis, has been verified by other authors.
Cowper’s Glands (Bulbo-Urethral): These glands are paired, oval structures about one and one-half by two and one-half centimeters in size, situated on either side of the dorsal pelvic part of the urethra close to the ischial arch. They are deeply embedded, with the bulbus urethae, in the bulbo-cavernosus muscle, thereby being inaccessible to palpation. In general, they are of a well developed anastomosing tubular type. The connective tissue stroma is relatively thin, and thickens only in between the larger lobules, where one finds the larger collecting ducts. Each gland opens by a single duct. The epithelium is of the simple cuboidal type. Little is known of the function of its secretion, though Kingsbury (30) regards it in the light of a mating gland; that is, it lubricates the genital passages during coitus, as does its homologous structure in the female, Bartholin’s gland.
Ellenberger describes the urethra, slit ventrally, as presenting the following picture: “The colliculus seminalis distinctly appears as a process or offshoot of the crista urethralis of the Trigonium Vesicae. At the summit, and at the bottom of the two slits, open laterally the ducts of the vesicles, and medially the ductus deferens.... From the caudal slope of the colliculus go two distinct mucous membrane folds which run through the entire pelvic urethra, near together, somewhat diverging, and then coming together, so that they form an elongated, narrow oval. At their caudal union, the excretory ducts of the bulbo-urethral glands open side by side. At the point of departure of the folds from the colliculus, arises a niche-shaped opening, between both folds, and likewise lateral to each fold. In these niches open the ducts of the prostate. The openings of the disseminate prostate lie in rows as in the horse, but form not less than six rows. There is one row medial to each fold, and two lateral. Mullet mentions only the medial rows. These rows extend to the opening of the ducts of Cowper’s glands. The stratum glandulare (disseminate prostate) is very easy to recognize with the naked eye.”
Semen: The semen is the mixed product of the testicles, their excretory passages, and the accessory sexual glands, a fact which complicates its study considerably. The freshly ejaculated fluid is cloudy, tenacious, more or less coagulable, and is rich in albumen. It is weakly alkaline in reaction, and contains eighty to ninety per cent of water. Of the solid constituents, there is forty per cent of ash, of which three-fourths is calcium phosphate. Besides the spermatozoa, the semen frequently contains epithelial cells, leucocytes, concentric amyloid concretions, and lecithin bodies. When cold, the characteristic phosphoric acid salts are precipitated. The fluid content is the product of the tubules of the testicles, their excretory ducts, and the accessory sexual glands. The characteristic odor of the semen is supplied by a slimy nucleoalbumen “spermin” which forms the spermatic crystals, and is furnished by the prostatic secretion.
During ejaculation the spermatozoa and secretions added by the testicle and epididymis are probably carried to the ampulla by peristaltic muscular action, in the earlier stages of the orgasm. At the height of the orgasm, the ampulla is emptied into the posterior urethra in common with the secretion of the contracting vesicles, here to be admixed with the thin prostatic secretion. The entire mixture is then propelled, and ejaculation produced by strong muscular contractions of the entire urethra. As was stated before, the semen is the product of the testicles, the excretory ducts, and the accessory sexual glands. The testes furnish the essential germinal elements, the sperms, and some of the fluid content. Then is added the product of the epididymis, vas, and ampulla, which stimulates the spermatozoa to active motility, nourishes the organisms, and adds somewhat to the fluid bulk of the secretion.
Stigler (25) states: “During its sojourn in the epididymis, the properties of the spermatozoa are modified; the motility, ability to resist heat, and other properties are augmented, at least in the case of the guinea pig, rat, and mouse.” To the secretion is then added the product of the vesicles, which contributes markedly to its fluid content, nourishes the sperms, and supplies the ferment which induces clotting of the semen when ejaculated. This is very important because the clot formed in the vagina protects the delicate spermatozoa from the hostile acid vaginal secretion. The prostate likewise adds bulk and nourishing substances, besides stimulating the spermatozoa to fuller and more lasting motility. The addition of the spermin is perhaps unimportant. The function of the secretion of the Cowper’s glands, which is added at this time, is problematical. It does, however, have a diluting action on the semen. Perhaps its secretion is poured out prior to ejaculation so as to lubricate the canal and prepare the way for the semen.
Fish (28) has demonstrated by means of darkfield illumination, the presence of numerous minute particles or ultraparticles in this fluid. Their character and significance are matters of conjecture, but it would seem as though they were not identical with the “chylomicrons” or fat particles found in the blood by Gage. Perhaps further researches will reveal some intimate connection between the number present in a field, and the relative potency of the animal.
Each portion of the tract furnishes some essential element to the mixed product which is so remarkably adapted both as a vehicle for the ejaculation of the spermatozoa, and as a fluid in which their motility is initiated and maintained. Any derangement of one part is fraught with danger to the existence of viable spermatozoa, and the continuation of full fertility on the part of the animal. The physiology of each contributing gland must be borne in mind at all times. Walker (31) investigated the fertility of the semen of the dog, taken from various parts of the tract. His results were: (1) semen from the testicle and head of the epididymis showed no motility, (2) semen from the tail of the epididymis showed some motility in the more fluid contents of the preparations, (3) semen from the vas deferens appeared about the same, (4) a mixture of epididymis semen and prostatic secretion showed active motility, and (5) likewise in a mixture of epididymis semen, though only in those places where the fluids had become well mixed. My observations, however, differ in one respect with regard to the bull, as I have found full motility of the spermatozoa from the epididymis, but it is not so lasting as when augmented by the addition of the prostatic fluid. Boettcher (32) concludes: “that the secretion of the accessory male genital organs possesses a protective colloid, which (1) hinders the spermatozoid action of the vaginal secretion, at least until the sperms have time to reach the interior of the uterus which is an alkaline reaction, (2) that it makes the ejaculate more voluminous, so that by cohabitation, a very good part of the vagina becomes moistened, and the spermatozoa become distributed over the greater part of the vaginal mucosa. This distribution is rendered necessary because some of the fluid flows from the vagina following coitus. In this manner the opportunity is given for a part of the ejaculate containing the spermatozoa to be brought easier to the external os, and (3) it happens that because of its content of sodium chloride the life of the spermatozoa is stimulated and prolonged.” A fuller discussion of the essential physiology of the various parts of the tract on the semen content, and fertility, will be taken up later. The changes in biochemical content, reaction, and the result of the addition of bacterial products will also be more fully discussed.
Spermatozoa: The history of the discovery of spermatozoa is very interesting, and for that reason a brief outline will be given. The “semen threads” were first observed in the year 1667, by Ham, a student of Leeuwenhoek at Leyden. The discovery was announced, confirmed by findings in the dog and rabbit, and discussed by the latter author under the title: Observationes Anthonii L. de natis e semine genitali animaculis (Upon the formation of young from procreative material). The sperms were taken to be animals on account of their motility, and their significance remained questionable if not unknown. Spallanzani, quoted by Marshall (29), was the first to show that the filtered fluid was impotent, and that spermatozoa in the semen were essential to fertilization. Kolliker, in 1841, discovered that the sperms arise from the cells of the testis, and Barry in 1843, observed the conjugation of sperm and ovum in the rabbit. This led to a clear understanding of the function of these important germinal elements.
The spermatozoa are the male procreative cells, and are characterized by the possession of a head containing the chromosomes necessary for fertilization, and a tail capable of propelling the organism on its way to meet the ovum. The length of the entire sperm, including the head, is seventy-five to eighty microns. The head is nine and five-tenths microns long, and five and five-tenths microns wide. It may be divided into two principal parts, the head and tail. The head, for the larger part, is made up of the nucleus, and may be differentiated by staining reactions into a darker staining posterior part, an anterior lighter part, and often a still lighter area between the two. On the anterior part is a sharpened edge, the acrosome, which serves to perforate the ovum. The whole is surrounded by a very definite limiting membrane which often becomes obscured under abnormal conditions. The tail may be divided into three parts: connecting piece, principal part, and terminal filament. The connecting piece, the essential motile apparatus, is the thickest and strongest part, and joins the tail proper to the head. It consists of the central axial filament, a spiral filament around this, and an outer mitochondrial covering. Anteriorly it is limited by the anterior portion of the posterior chromosome, and posteriorly by the annular chromosome. The anterior chromosome is directly connected with the head, there appearing a light break here at the neck where separation frequently occurs. This neck serves as a joint for the motion. The axial filament, therefore, does not reach the head, but extends back from the anterior part of the posterior chromosome. The principal part consists merely of the axial filament, and a thin outer covering, while the end piece is quite thin and is made up solely of the uncovered axial filament. The finer structures are seen only when special staining reactions are used, and then only when the sperms are obtained directly from the testicle. The function of the sperms is of course primarily that of fertilization. Numerous observers have, however, thought that they might have some other definite, though unknown, use.
An editorial in the Journal of the American Medical Association (33) raises several important questions regarding this obscure phenomenon. The fact that an enormous number of spermatozoa are produced, and only one, or at most, a few perform the function of fertilization, raises the question as to what becomes of the remainder. It is stated: “Zoologists have found that in some of the invertebrates the spermatozoa invade the entire body of the female, and in some species they reach the ovum by penetrating the cuticle from outside and migrating to their goal. Studies on rodents show that the sperms invade the epithelium of the generative mucosa and underlying connective tissue. These tissues seemed to be stimulated to growth, suggesting that this may influence the uterine mucosa in its preparation for receiving and embedding the egg, and in forming the decidua.” It has been shown that the sperms contain a specific protein capable of producing antibodies in the blood plasma, by citing the fact that rabbits develop a distinct Aberhalden reaction for testicular proteins shortly after cohabitation. One very important observation showed that by immunizing female rabbits with sperms they were rendered sterile for some time, although after a few months they again became capable of impregnation. The question raised is: “... if the spermatozoa invade the female tissues and cause the formation of specific antibodies which are capable of preventing fertilization, may not such a process participate in the problem of sterility?” This very problem seems to be a factor in explaining why some couples who are not fertile to each other subsequently are both fertile when they cohabit with other individuals.
Motility: After clinical observation of the motility of the spermatozoa of the bull, I find that it differs little or none from the types as observed by Reynolds (34) in his work on human spermatozoa. His observations are so accurate and well described that they will be given in his words. “All normal motions appear to be consecutive phases. Initial motion, i. e., motion as seen in fresh semen under favorable conditions, consists of a lashing of the after part of the tail from side to side which is so rapid as to constitute vibration. It produces rapid forward motion in a practically straight line, the head, middle piece, and forward portion of the tail maintaining their position in the line of motion with practically no swaying from side to side. The action of the flagellum is so rapid that it is quite impossible to follow its individual movements. Spermatozoa swimming in this manner head against the current and usually cross the field of observation in about five seconds in the absence of currents or obstacles. This type of motion will be described throughout the paper as ‘progressive vibratile’ motion. Progressive vibratile motion is normally succeeded after a variable length of time by what I regard as the second phase of normal motion.
“The second normal motion differs from the first not only in its character but in markedly reduced speed. The tail movement alters to a long stroke from side to side and almost the whole length of the tail partakes in the stroke. This is, moreover, accompanied by swaying of the head and middle piece through an arc which is always considerable and may even equal ninety degrees. The general outline of the spermatozoa, from being practically straight with almost non-detectable sharp, quick, small arc vibration of the after-tail, has become an S in outline, with large, slow, plainly perceptible undulations traveling gradually backward throughout the length of the spermatozoon. Speed has been lost and direction seems to be more specifically determined by the surroundings. Individuals at this stage show a pronounced choice of direction and go up to objects in the medium, from which they later make off as though the movement were determined by tactile reaction to some extent. This type of motion has, therefore, been named ‘undulatory tactile’ in contradistinction to ‘progressive vibratile.’
“The third type of normal motion succeeds the second and consists in a tendency on the part of the spermatozoon to push itself against or into any small masses of cells, or sometimes other materials, which it may find in the neighborhood, bunting itself into any small cove that can be found, and maintaining a slight burrowing motion by a lashing tail movement of the vibratile type not unlike the movements of the caudal fin of a fish. The movement of the flagellum in this third type is unlike the second type in that it is vibratile rather than lashing, but is slower than the vibratile motion of the first type and less limited to the afterpart of the tail. These spermatozoa are apparently not caught in the debris or unable to move off. From time to time, they back out of such a cove and seek another mooring place.
“This ‘stationary hunting’ motion is less universal than the other two. Many individual spermatozoa fail to attain it. It seems probable that only the most vigorous individuals ever reach this stair”. It has not been encountered in unmixed semen or in any artificial mediums. It has been observed only when the spermatozoon is in the secretions of the female genital tract. It is most frequent when the spermatozoon is in contact with a nest of epithelial cells....
“The three types of normal motion are not only distinctive but are always consecutive, i. e., the second follows the first after a period which is apparently determined both by initial vitality and by the favorable or unfavorable character of the medium, while the third has been observed to occur only in individuals which have already developed the second. They apparently constitute a normal cycle.
“This cycle is open to the theoretical explanation that these types of motion are directly adapted to the function of the spermatozoon; thus, the progressive vibratile motion which is characteristic of the earliest period of its existence appears especially suitable for its prolonged journey through the cervix and uterus to the fundus and tube. This is supported by the fact that during this motion it always heads directly against any existing current, and that during this stage of its journey it must under natural conditions be continuously exposed to the faint outward ciliary currents of the mucous membrane of these passages.
“The undulatory tactile motion which succeeds the progressive vibratile would then be well adapted to the later stage in which the spermatozoon has reached the tube, where its success in conjugation is dependent on its finding the ovum rather than on further progress.
“The stationary bunting type of motion is that which would be demanded by the passage of the spermatozoon through the egg membrane which has been so often observed in the lower animals. This very plausible explanation is, however, necessarily theoretical and must always remain so, as the conditions which surround the specimen on the field of the microscope vary in so many respects from those in which it accomplishes conjugation in the course of nature; but the practical importance of the study of types of motion is not affected by their explanation.”
The duration of motility is a variable factor, dependent entirely upon the environment in which the spermatozoa are placed. Within the body they usually survive at least a week. One author describes a case in which he found living sperms in a woman who stated that coition had not been experienced for three and one-half weeks. It has been stated with regard to human sperms, that their motion should continue or be capable of being re-established for twelve hours. Cary (35) states, “first, that in their proper medium and at the body temperature the viability of the sperm cells may extend over a period of a few days; second, that their prolonged vitality is probably dependent upon the normal lime salts of the prostatic fluid; third, that the sustaining power of the seminal fluid is increased by its union with the normal secretion of the female genital tract.” After death of the male animal they retain their motility in the genital tract for twenty-four to forty-eight hours.
Wolf (36) worked on this problem in rabbits, and summarizes as follows: “The motility of rabbit spermatozoa can be preserved for at least nine days by placing the juice of the epididymis in the Tyrode solution which had been buffered and to which glucose had been added. The solution is adjusted to a pH of about 7.4. Oxygen is passed in and a suitable amount of sodium bicarbonate added. The preparation must be kept at a temperature near the freezing point of water.” Under ordinary conditions motility persists outside the body only a few hours after ejaculation, but if the semen is kept quite cool till the time of examination on a warm stage, motility should be capable of being restored in at least a fair percentage of the sperms for twenty-four to forty-eight hours. The cells are more sensitive to heat than to cold, and even to dilute acids more than to alkalies.
Henle (quoted by Ellenberger) states that a spermatozoon under favorable conditions travels at the rate of twenty-seven millimeters in seven and one-half minutes, which makes three and five-tenths millimeters per minute. This is about sixty times the entire length of the spermatozoon, and twenty-one centimeters in an hour. Forward motion is also more pronounced when the swim is against the current, such as is produced by the cilia of the oviduct. It has been demonstrated that feebly motile sperms become very actively motile when placed on the mucosa of a fresh Fallopian tube.