Essays In Pastoral Medicine

by Austin O'Malley; James J. Walsh

The human ovum and spermatozoon are single cells, and the principal parts of a typical cell are the cytoplasm (called also the protoplasm), and, within this, the nucleus and centrosome. The centrosome is efficient in the process of cell-division. A few cells have also an outer envelope or membrane, and this part is well developed in the ovum.
The nucleus is the centre of activity in a cell. In the resting state it is surrounded by a membrane, and within the membrane is an intra-nuclear network made up of chromatin and linin—the chromatin is an important element. The meshes of this network are probably filled with fluid.
During the stages preparatory to the mitotic, or indirect, division of a cell into two cells (one of the methods of reproduction) the chromatin segregates in typical cases into two groups of loops, and each group has equal portions of the chromatin. When the chromatin is in this shape, a loop is called a chromosome.
The chromosomes are very important. They occur in constant definite numbers in the somatic cells of the various species of many animals and plants, and it is probable that each species of plant and animal has its own characteristic number of chromosomes. Wilson (The Cell in Development and Inheritance, New York, 1890) gives a list of 72 species in which the number has been determined. Man has probably 16 chromosomes in the somatic cell, and the mature male and female germ cells in man contribute eight chromosomes each to the nucleus of the impregnated ovum.

The chromosomes transmit the physical bases of heredity from one generation to the next, and the heritages from the two parents are equal except in cases of prepotency. Every cell [{71}] in the human body is derived from the father and the mother equally. The fact that the woman carries a child for months in her womb means only that she employs a peculiar method of feeding and protecting it. After its birth she feeds it from her breasts, before birth through its umbilical vessels, but she originally gives only the eight chromosomes as the father does, and the child's vital principle builds up the body from this foundation. The popular notion that the foetus in the womb is formed through some process of literal abstraction from the maternal tissues is no more true than that the infant is so built up while it is suckling; both processes are merely different methods of feeding.

All the chromosomes from the fathers of at least 200 men could fit simultaneously on the head of one pin, yet virtually, not merely potentially, half the bodily substance of that multitude, and all the physical characteristics derived from the 200 fathers, are indubitably contained in those chromosomes and nowhere else, unless by a special creation they are infused with the new soul, which seems to be an altogether unreasonable alternative. This statement concerning the minuteness of the chromosomes is not speculation—they can readily be seen and measured with the aid of the microscope.

A human being, then, obtains eight microscopic chromosomes from his father and eight from his mother, positively nothing more except food; yet he develops into a man with a body made up of countless millions of cells which expand into more than 200 bones in the skeleton and over 200 muscles,—into the fascias, ligaments, tendons, the great and small glands, the lymph and blood systems, the respiratory and alimentary tracts, the skin and its appendages, and a nervous system, which alone furnishes material for years of study if we would learn its anatomy fully. Not only all this, but the man commonly closely resembles his father or his mother, or some other ancestor, in personal appearance, in certain physical tendencies, in graces or blemishes; and furthermore, he shows inherited racial characteristics.

If a father is prepotent, he may have a greater effect in producing the formed child than the mother has, and vice versa, as when a son closely resembles his father or his mother. [{72}] Prepotency, moreover, may extend down through generations and centuries. In the streets of Palermo to-day typical Normans may be seen, despite the intermarriages of centuries, who are the descendants of those male Normans that went down to Sicily with Tancred. There are Romans there, too, and Saracens. When the Belgae—a race of tall, red-bearded men, with elliptical skulls—went from the continent of Europe to Ireland, probably six centuries before our era, they conquered the aborigines, a gentle, brune race of lower stature. These Belgae became the ancestors of the chieftain class, and their physical type persists until to-day; so does that of the Pictish aborigines. Daniel O'Connell had a typical Belgic body. Other big, blond Irishmen are Norse or Danish in remote origin.

How is the extremely complex human body with its various physical characteristics built up from the nucleus of a fecundated cell, the ovum? The endeavour to answer this question has brought out most ingenious speculation from nearly all the great biologists of modern times. The question is the foundation of the theories of heredity, and it is also fundamental in the theories of evolution.
The human ovum is a flattened spherical cell, made up of a very delicate cell-wall, called the vitelline membrane; outside this is a comparatively thick membrane, the zona pellucida, which is properly not a part of the cell. Within the vitelline membrane is a granular cytoplasm, the vitellus (yolk), and in this lies the nucleus, which in the old text-books was called the germinal vesicle. This nucleus contains a nucleolus.
The human spermatozoon consists of a flattened head which has a thin protoplasmic cap extending down two-thirds of its length. In the head is the nucleus with the chromatin. Beyond the head is the neck, which contains the anterior and posterior centrosomes. Behind the neck is the tail, or flagellum, in three parts,—the middle piece, the principal part, and the end piece. From the neck to the end of the tail centrally runs a bundle of fibrils, the axial filament. In the middle piece these fibrils are wrapped within a single spiral filament which winds from the neck down to the annulus at the beginning of the principal part, and lies in a clear fluid. Without the spiral filament, along the middle piece, is the mitochondria, a finely granular protoplasmic layer. The principal part of the tail consists of the axial [{73}] filament enclosed in an involucrum, and the end piece is made up of this filament without the involucrum.
The head and neck of the spermatozoon, which contain the nucleus and centrosomes, are the essential parts, and the middle piece and the remainder of the tail appear to be used solely for locomotion and penetration. When the head penetrates the ovum, the tail is detached and rejected.
Our knowledge of the initial stages in the development of a human embryo is derived indirectly from the observation of other mammals. There are nine early human embryos reported, and the average probable age of these is twelve days. Breuss' specimen was probably ten days old (Wiener med. Wochenblatt, 1877). Peters (Einbettung des mensch. Eies, 1899) found a smaller embryo than this. The Breuss ovum was 5 mm. in length; Peters' was 3 by 1.5 by 1.5 mm., but the probable age was not given. There have been numerous embryos more than twelve days old observed, and since the process after the twelfth day is identical in man and the higher mammals, there is no doubt that the first stages are also the same.
The segmentation that makes new cells is complicated, and the outcome of the division is a ball of cells. In eggs which have a large yolk, like those of birds, the cells form a round body resting on the surface of the yolk, but in mammalian ova a hollow ball of cells, or a Morula, results, which lines the internal surface of the cellular envelope. The ovum absorbs moisture by osmosis and enlarges, and about the twelfth day after the germ-nuclei have begun to divide, the Morula, or hollow ball of cells, called also the Blastodermic Vesicle, is formed.
The next stage in development is the establishment of two primary germinal layers, called together the Gastrula, The outer layer is the Ectoderm or the Epiblast, and the inner layer is the Endoderm or Hypoblast. In a Morula the smaller cells, which contain less yolk-material, gradually grow around the larger yolk-containing cells to form the Gastrula.
Between the Ectoderm and the Endoderm a layer of cells called the Mesoderm or Mesoblast is next formed, and from these three layers all the parts of the embryo are built up. From the outer Ectoderm and the inner Endoderm those organs arise which are in the body, outer and inner,—as the nervous system and the outer skin from the Ectoderm, the inner entrails, the lungs and liver, from the Endoderm. From the Mesoderm come the inner skin, the bones and muscles.
By this time the embryo is a minute longitudinal streak at the [{74}] surface of one pole of the ovum. The "Primitive Trace" is like a long inverted letter U, the legs of which are in apposition. The Primitive Trace becomes a circular flattened disc; and it grows into a cylindrical body by the juncture of the free margins which fold downward and inward and meet in the median line, and this closes in the pelvic, abdominal, thoracic, pharyngeal, and oral cavities. The legs and arms bud from this cylinder later. While the ventral cylinder is growing, another longitudinal cylinder is formed along the upper surface of the embryo, which will contain the brain and the spinal column. The subsequent development of the embryo and foetus need not be known for an understanding of the material considered in treating here of terata.

Human terata occur in certain rather definite, types of erroneous development, and the classification of Hirst and Piersol (Human Monstrosities, Philadelphia, 1891), which is a combination and change of the classifications of Geoffrey Saint-Hilaire, Klebs, and Förster, is the most satisfactory. There are four great groups of abnormally developed human beings: (1) Hemiteratic; (2) Heterotaxic; (3) Hermaphroditic; (4) Monstrous.

Hemiterata are giants, dwarfs, persons showing anomalies in shape, in colour, in closure of embryonic clefts, in absence or excess of digits, or having other defects. This group does not come under discussion here, but attention should be called to the fact that women who are dwarfs are to be warned before marriage that they cannot be delivered normally,—that the caesarean section or symphyseotomy will be necessary, or that certain physicians will practise craniotomy in delivering them.

The Heterotaxic group comprises persons whose left or right visceral organs are reversed in position through abnormal embryonic development; the liver is on the left side, the heart points to the right, and so on.

Of the next group, the Hermaphroditic, it may be said that a true hermaphrodite, in the full sense of the term, has not been found; but there have been several examples of individuals who had an ovary and a testicle, and other rudimentary sexual organs that belonged to both male and female. Forms of apparent doubling are common, and in case of doubt as to sex the probability leans toward the [{75}] masculine side. As to marriage in such cases, questions may arise that are to be settled by the anatomist. In dealing with double monsters it is sometimes difficult or impossible to determine whether we have to do with one or two individuals, and this difficulty has serious weight, especially in the administration of baptism. It is improbable that there is a doubling of personality in hermaphrodites. A striking characteristic of compound terata is that the individuals are always of the same sex; moreover, the embryonal development of reproductive organs in general is such as almost to preclude a question of duality of personality.