Some organs that are, as far as regards their functions, peculiar and essential to one sex only, are nevertheless found to be repeated in the opposite sex in the form of an analogous rudimentary type of structure. Thus, in the male we may observe the unity of sexual struc ture maintained in the presence of the rudi ments of the mammary gland, which is .fitnc tiondly an organ of the female system only. In the human subject, and in animals whose females have pectoral mamma:, these organs occupy the same position in the male; while in those species of quadrupeds in which they are placed in the inguinal region, we find them in the corresponding males forming the scrotum or bags containing the testicles. IIence, as we have already seen, the testicles, in cases of mal formation in these animals, are often laid upon or imbedded in the udder. In the same way in the Marsupiata, the bone which the female has for supporting the marsupium is repeated in the organization of the male, although in the latter we cannot conceive it to serve any possible use./ In the female also we observe in some points a similar disposition to the rudimentary repe tition of parts that are essential or peculiar only to the male organization, as in the repeti tion in the clitoris of some female Itodentia, of the penis-bone of the male, and in the forma tion of rudimentary forms of those processes of peritoumum which constitute the tunic vaginales. We are ourselves inclined also to regard the common crescentic form of the hy men of the human female in the same light,§ and to consider it merely as an abortive attempt at that closure of the perinmal fissure which we have already described as effected at an early period in the male embryo—an opinion in which we conceive we are borne out both by the history of the development and the study of the malformations of the external sexual parts in the female.
M. Isidore St. Hilaire read, irf 1833, to the French Academy a memoir,' in which, follow ing up the doctrine of his father with regard to the determination and distinction of the type of parts by the particular vessels distributed to them, he endeavoured to thew some new points of analogy between the male and female organs, and to develop new views with regard to the origin and particular varieties of herma phroditic malformations. With Ilurdach, he divides the whole reproductive apparatus of either sex into three transverse spheres and into six portions or segments in all, or three on each side, viz., 1 and 2, the deep organs, in cluding the male testicles and female ovaries ; 2 and 3, the middle organs, or male prostate and vesiculm seminales, and female uterus ; 3 and 4, the external organs, comprehending the penis and scrotum of the male, and the clitoris and vulva of the female. Each of these portions or segments is, M. St. Hilaire points out, supplied by an arterial trunk peculiar to itself, and the corresponding organs of the male and female by corresponding arterial branches, as the deep organs of both sexes by the two spermatics, the middle by branches of the two hypogastrics, and the external by some other hypogastric branches, and by the external pu dies. This circumstance, he conceives, renders
all the segments in a certain degree independ ent of the others, both as regards their develop ment and existence, and allows of the occa sional evolution of any one or more of them on a type of sexual structure, different from that upon which the others are formed in the same individual.
Though assuredly we cannot subscrihe to the speculations of the elder St. Hilaire, that the development in the embryo of male testi cles or female ovaries, and consequently the whole determination of the sex, is originally re gulated by the mere relative angle at which the first two branches of the spermatic arteries come off, and the kind of course which they follow,1- (more particularly as it is admitted by most physiologists that the bloodvessels grow, not from their larger trunks or branches towards their smaller, but from their capillary extremi ties towards their larger branches,) yet we believe that the doctrine of the comparative independence of the different segments of the reproductive organs pointed out by the son is in its general principles correct. At the same time we would here remark that we conceive the doctrine would have been founded more on truth if the influence of the nervous branches supplying the different reproductive organs bad been taken into account along with that of their arterial vessels, because, as we shall point out when speaking of the causes of her maphroditism, there appears to be some con nection between the state of the nervous sys tem and the degree or condition of sexual de velopment.
The consideration of the preceding ana logies in structure between the male and female organs is interesting in itself, and, as far as relates to our present subject, important in this respect, that it enables us in some degree to understand how it happens that, without any actual monstrous duplicity, we should some times find, in an organization essentially male, one or more of the genital organs absent and replaced by an imperfect or neutral organ, or by the corresponding organ of the opposite sex, and vice versa ; inasmuch as it shews us that the moulds in which the analogous organs of the two sexes are formed are originally the same. Hence there is no difficulty in con ceiving that, in the body of the same individual, the primitive structural elements of these parts should occasionally, in one or more points or segments, take on, in the process of development, a different sexual type from that which they assume at other points. Indeed some physi ologists, as we shall immediately see, deny that the most complete hermaphroditic malfor mations ever consist of anything except such a want of conformity between the sexual type of different portions of the reproductive appa ratus.