I now turn to a very much more serious and elaborate attempt to define the constitution of the sexual impulse, that of Moll. He finds that it is made up of two separate components, each of which may be looked upon as an uncontrollable impulse.[[19]] One of these is that by which the tension of the sexual organs is spasmodically relieved; this he calls the impulse of detumescence,[[20]] and he regards it as primary, resembling the impulse to empty a full bladder. The other impulse is the "instinct to approach, touch, and kiss another person, usually of the opposite sex"; this he terms the impulse of contrectation, and he includes under this head not only the tendency to general physical contact, but also the psychic inclination to become generally interested in a person of the opposite sex. Each of these primary impulses Moll regards as forming a constituent of the sexual instinct in both men and women. It seems to me undoubtedly true that these two impulses do correspond to the essential phenomena. The awkward and unsatisfactory part of Moll's analysis is the relation of the one to the other. It is true that he traces both impulses back to the sexual glands, that of detumescence directly, that of contrectation indirectly; but evidently he does not regard them as intimately related to each other; he insists on the fact that they may exist apart from each other, that they do not appear synchronously in youth: the contrectation impulse he regards as secondary; it is, he states, an indirect result of the sexual glands, "only to be understood by the developmental history of these glands and the object which they subserve"; that is to say, that it is connected with the rise of the sexual method of reproduction and the desirability of the mingling of the two sexes in procreation, while the impulse of detumescence arose before the sexual method of reproduction had appeared; thus the contrectation impulse was propagated by natural selection together with the sexual method of reproduction. The impulse of contrectation is secondary, and Moll even regards it as a secondary sexual character.
While, therefore, this analysis seems to include all the phenomena and to be worthy of very careful study as a serious and elaborate attempt to present an adequate psychological definition of the sexual impulse, it scarcely seems to me that we can accept it in precisely the form in which Moll presents it. I believe, however, that by analyzing the process a little more minutely we shall find that these two constituents of the sexual impulse are really much more intimately associated than at the first glance appears, and that we need by no means go back to the time when the sexual method of reproduction arose to explain the significance of the phenomena which Moll includes under the term contrectation.
To discover the true significance of the phenomena in men it is necessary to observe carefully the phenomena of love-making not only among men, but among animals, in which the impulse of contrectation plays a very large part, and involves an enormous expenditure of energy. Darwin was the first to present a comprehensive view of, at all events a certain group of, the phenomena of contrectation in animals; on his interpretation of those phenomena he founded his famous theory of sexual selection. We are not primarily concerned with that theory; but the facts on which Darwin based his theory lie at the very roots of our subject, and we are bound to consider their psychological significance. In the first place, since these phenomena are specially associated with Darwin's name, it may not be out of place to ask what Darwin himself considered to be their psychological significance. It is a somewhat important question, even for those who are mainly concerned with the validity of the theory which Darwin established on those facts, but so far as I know it has not hitherto been asked. I find that a careful perusal of the Descent of Man reveals the presence in Darwin's mind of two quite distinct theories, neither of them fully developed, as to the psychological meaning of the facts he was collecting. The two following groups of extracts will serve to show this very conclusively: "The lower animals have a sense of beauty," he declares, "powers of discrimination and taste on the part of the female" (p. 211[[21]]); "the females habitually or occasionally prefer the more beautiful males," "there is little improbability in the females of insects appreciating beauty in form or color" (p. 329); he speaks of birds as the most "esthetic" of all animals excepting man, and adds that they have "nearly the same taste for the beautiful as we have" (p. 359); he remarks that a change of any kind in the structure or color of the male bird "appears to have been admired by the female" (p. 385). He speaks of the female Argus pheasant as possessing "this almost human degree of taste." Birds, again, "seem to have some taste for the beautiful both in color and sound," and "we ought not to feel too sure that the female does not attend to each detail of beauty" (p. 421). Novelty, he says, is "admired by birds for its own sake" (p. 495). "Birds have fine powers of discrimination and in some few instances it can be shown that they have a taste for the beautiful" (p. 496). The "esthetic capacity" of female animals has been advanced by exercise just as our own taste has improved (p. 616). On the other hand, we find running throughout the book quite another idea. Of cicadas he tells us that it is probable that, "like female birds, they are excited or allured by the male with the most attractive voice" (p. 282); and, coming to Locustidæ, he states that "all observers agree that the sounds serve either to call or excite the mute females" (p. 283). Of birds he says, "I am led to believe that the females prefer or are most excited by the more brilliant males" (p. 316). Among birds also the males "endeavor to charm or excite their mates by love-notes," etc., and "the females are excited by certain males, and thus unconsciously prefer them" (p. 367), while ornaments of all kinds "apparently serve to excite, attract, or fascinate the female" (p. 394). In a supplemental note, also, written in 1876, five years after the first publication of the Descent of Man, and therefore a late statement of his views, Darwin remarks that "no supporter of the principle of sexual selection believes that the females select particular points of beauty in the males; they are merely excited or attracted in a greater degree by one male than by another, and this seems often to depend, especially with birds, on brilliant coloring" (p. 623). Thus, on the one hand, Darwin interprets the phenomena as involving a real esthetic element, a taste for the beautiful; on the other hand, he states, without apparently any clear perception that the two views are quite distinct, that the colors and sounds and other characteristics of the male are not an appeal to any esthetic sense of the female, but an appeal to her sexual emotions, a stimulus to sexual excitement, an allurement to sexual contact. According to the first theory, the female admires beauty, consciously or unconsciously, and selects the most beautiful partner[[22]]; according to the second theory, there is no esthetic question involved, but the female is unconsciously influenced by the most powerful or complex organic stimulus to which she is subjected. There can be no question that it is the second, and not the first, of these two views which we are justified in accepting. Darwin, it must be remembered, was not a psychologist, and he lived before the methods of comparative psychology had begun to be developed; had he written twenty years later we may be sure he would never have used so incautiously some of the vague and hazardous expressions I have quoted. He certainly injured his theory of sexual selection by stating it in too anthropomorphic language, by insisting on "choice," "preference," "esthetic sense," etc. There is no need whatever to burden any statement of the actual facts by such terms borrowed from human psychology. The female responds to the stimulation of the male at the right moment just as the tree responds to the stimulation of the warmest days in spring. We should but obscure this fact by stating that the tree "chooses" the most beautiful days on which to put forth its young sprouts. In explaining the correlation between responsive females and accomplished males the supposition of esthetic choice is equally unnecessary. It is, however, interesting to observe that, though Darwin failed to see that the love-combats, pursuits, dances, and parades of the males served as a method of stimulating the impulse of contrectation—or, as it would be better to term it, tumescence—in the male himself,[[23]] he to some extent realized the part thus played in exciting the equally necessary activity of tumescence in the female.
The justification for using the term "tumescence," which I here propose, is to be found in the fact that vascular congestion, more especially of the parts related to generation, is an essential preliminary to acute sexual desire. This is clearly brought out in Heape's careful study of the "sexual season" in mammals. Heape distinguishes between the "pro-estrum," or preliminary period of congestion, in female animals and the immediately following "estrus," or period of desire. The latter period is the result of the former, and, among the lower animals at all events, intercourse only takes place during the estrus, not during the pro-estrum. Tumescence must thus be obtained before desire can become acute, and courtship runs pari passu with physiological processes. "Normal estrus," Heape states, "occurs in conjunction with certain changes in the uterine tissue, and this is accompanied by congestion and stimulation or irritation of the copulatory organs.... Congestion is invariably present and is an essential condition.... The first sign of pro-estrum noticed in the lower mammals is a swollen and congested vulva and a general restlessness, excitement, or uneasiness. There are other signs familiar to breeders of various mammals, such as the congested conjunctiva of the rabbit's eye and the drooping ears of the pig. Many monkeys exhibit congestion of the face and nipples, as well as of the buttocks, thighs, and neighboring parts; sometimes they are congested to a very marked extent, and in some species a swelling, occasionally prodigious, of the soft tissues round the anal and generative openings, which is also at the time brilliantly congested, indicates the progress of the pro-estrum.... The growth of the stroma-tissue [in the uterus of monkeys during the pro-estrum] is rapidly followed by an increase in the number and size of the vessels of the stroma; the whole becomes richly supplied with blood, and the surface is flushed and highly vascular. This process goes on until the whole of the internal stroma becomes tense and brilliantly injected with blood.... In all essential points the menstruation or pro-estrum of the human female is identical with that of monkeys.... Estrus is possible only after the changes due to pro-estrum have taken place in the uterus. A wave of disturbance, at first evident in the external generative organs, extends to the uterus, and after the various phases of pro-estrum have been gone through in that organ, and the excitement there is subsiding, it would seem as if the external organs gain renewed stimulus, and it is then that estrus takes place.... In all animals which have been investigated coition is not allowed by the female until some time after the swelling and congestion of the vulva and surrounding tissue are first demonstrated, and in those animals which suffer from a considerable discharge of blood the main portion of that discharge, if not the whole of it, will be evacuated before sexual intercourse is allowed." (W. Heape, "The 'Sexual Season' of Mammals," Quarterly Journal of Microscopical Science, vol. xliv, Part I, 1900. Estrus has since been fully discussed in Marshall's Physiology of Reproduction.) This description clearly brings out the fundamentally vascular character of the process I have termed "tumescence"; it must be added, however, that in man the nervous elements in the process tend to become more conspicuous, and more or less obliterate these primitive limitations of sexual desire. (See "Sexual Periodicity" in the first volume of these Studies.)
Moll subsequently restated his position with reference to my somewhat different analysis of the sexual impulse, still maintaining his original view ("Analyse des Geschlechtstriebes," Medizinische Klinik, Nos. 12 and 13, 1905; also Geschlecht und Gesellschaft, vol. ii, Nos. 9 and 10). Numa Praetorius (Jahrbuch für Sexeuelle Zwischenstufen, 1904, p. 592) accepts contrectation, tumescence, and detumescence as all being stages in the same process, contrectation, which he defines as the sexual craving for a definite individual, coming first. Robert Müller (Sexualbiologie, 1907, p. 37) criticises Moll much in the same sense as I have done and considers that contrectation and detumescence cannot be separated, but are two expressions of the same impulse; so also Max Katte, "Die Präliminarien des Geschlechtsaktes," Zeitschrift für Sexualwissenschaft, Oct., 1908, and G. Saint-Paul, L'Homosexualité et les Types Homosexuels, 1910, p. 390.
While I regard Moll's analysis as a valuable contribution to the elucidation of the sexual impulse, I must repeat that I cannot regard it as final or completely adequate. As I understand the process, contrectation is an incident in the development of tumescence, an extremely important incident indeed, but not an absolutely fundamental and primitive part of it. It is equally an incident, highly important though not primitive and fundamental, of detumescence. Contrectation, from first to last; furnishes the best conditions for the exercise of the sexual process, but it is not an absolutely essential part of the process and in the early stages of zoölogical development it had no existence at all. Tumescence and detumescence are alike fundamental, primitive, and essential; in resting the sexual impulse on these necessarily connected processes we are basing ourselves on the solid bedrock of nature.
Moreover, of the two processes, tumescence, which in time comes first, is by far the most important, and nearly the whole of sexual psychology is rooted in it. To assert, with Moll, that the sexual process may be analyzed into contrectation and detumescence alone is to omit the most essential part of the process. It is much the same as to analyze the mechanism of a gun into probable contact with the hand, and a more or less independent discharge, omitting all reference to the loading of the gun. The essential elements are the loading and the discharging. Contrectation is a part of loading, though not a necessary part, since the loading may be effected mechanically. But to understand the process of firing a gun and to comprehend the mechanism of the discharge, we must insist on the act of loading and not merely on the contact of the hand. So it is in analyzing the sexual impulse. Contrectation is indeed highly important, but it is important only in so far as it aids tumescence, and so may be subordinated to tumescence, exactly as it may also be subordinated to detumescence. It is tumescence which is the really essential part of the process, and we cannot afford, with Moll, to ignore it altogether.
Wallace opposed Darwin's theory of sexual selection, but it can scarcely be said that his attitude toward it bears critical examination. On the one hand, as has already been noted, he saw but one side of that theory and that the unessential side, and, on the other hand, his own view really coincided with the more essential elements in Darwin's theory. In his Tropical Nature he admitted that the male's "persistency and energy win the day," and also that this "vigor and liveliness" of the male are usually associated with intense coloration, while twenty years later (in his Darwinism) he admitted also that it is highly probable that the female is pleased or excited by the male's display. But all that is really essential in Darwin's theory is involved, directly or indirectly, in these admissions.
Espinas, in 1878, in his suggestive book, Des Sociétés Animales, described the odors, colors and forms, sounds, games, parades, and mock battles of animals, approaching the subject in a somewhat more psychological spirit than either Darwin or Wallace, and he somewhat more clearly apprehended the object of these phenomena in producing mutual excitement and stimulating tumescence. He noted the significance of the action of the hermaphroditic snails in inserting their darts into each other's flesh near the vulva in order to cause preliminary excitation. He remarks of this whole group of phenomena: "It is the preliminary of sexual union, it constitutes the first act of it. By it the image of the male is graven on the consciousness of the female, and in a manner impregnates it, so as to determine there, as the effects of this representation descend to the depths of the organism, the physiological modifications necessary to fecundation." Beaunis, again, in an analysis of the sexual sensations, was inclined to think that the dances and parades of the male are solely intended to excite the female, not perceiving, however, that they at the same time serve to further excite the male also.[[24]]
A better and more comprehensive statement was reached by Tillier, who, to some extent, may be said to have anticipated Groos. Darwin, Tillier pointed out, had not sufficiently taken into account the coexistence of combat and courtship, nor the order of the phenomena. Courtship without combat, Tillier argued, is rare; "there is a normal coexistence of combat and courtship."[[25]] Moreover, he proceeded, force is the chief factor in determining the possession of the female by the male, who in some species is even prepared to exert force on her; so that the female has little opportunity of sexual selection, though she is always present at these combats. He then emphasized the significant fact that courtship takes place long after pairing has ceased, and the question of selection thus been eliminated. The object of courtship, he concluded, is not sexual selection by the female, but the sexual excitement of both male and female, such excitement, he asserted, not only rendering coupling easier, but favoring fecundation. Modesty, also, Tillier further argued, again anticipating Groos, works toward the same end; it renders the male more ardent, and by retarding coupling may also increase the secretions of the sexual glands and favor the chances of reproduction.[[26]]