DEVELOPMENT OF THE EMBRYO. 1005 



as to resemble the female vagina, whilst the penis is itself destitute of any trace 

 of the urethral canal; in some of these cases, again, the testes have not descended 

 into the scrotum ; whilst the absence of beard, the shrillness of the voice, and 

 the fulness of the mammae, have contributed to impart a feminine character to 

 these individuals, their male attributes, however, being determined by the semi- 

 niferous character of the essential organ, the testes. 1 In the female organs, on 

 the other hand, a greater or less degree of resemblance to those of the male may 

 be produced by the enlargement of the clitoris, by its furrowing or complete 

 perforation by the urethra, by the closure of the entrance of the vagina and the 

 cohesion of the labia, so as to present a likeness to the unfissured perineum and 

 scrotum of the male, by the descent of the ovaries through the inguinal ring 

 into the position of the male testes, by the imperfect development of the uterus 

 and mammae ; and with these are usually associated roughness of the voice and 

 growth of hair on the chin, and a psychical character more or less virile. True 

 Hermaphrodism, in which there is an absolute combination of the essential male 

 and female organs in the same individual, is comparatively rare. It may occur 

 under the forms of lateral hermaphrodism, in which there is a genuine ovary 

 on one side and a testis on the other, in which case the external organs are 

 usually those of a hypospadic male; transverse hermaphrodism, in which the 

 external and internal organs do not correspond, the former being male and the 

 latter female, or vice versa; and double or vertical hermaphrodism, in which 

 the proper organs characteristic of one sex have existed, with the addition of 

 some of those of the other ; this is the rarest of all, and it is not certain that 

 the coexistence of testes and ovaria on the same side has ever been observed in 

 the Human species. 3 



1010. We have now to follow the course of the development of the principal 

 organs of Animal life ; and shall first notice that of the Skeleton. We have 

 seen that, in the embryo of the Vertebrated animal, the future vertebral column 

 is marked out at an earlier period than any other permanent organ ( 997) ; 

 and that indications of a division into vertebrae are very speedily presented in 

 the embryo of the higher classes. The earliest formation, however, is one of 

 which we recognize no traces in the adult condition of Man ; namely, a longitu- 

 dinal column, tapering off to a point at the cranial and caudal extremities of the 

 embryo, and occupying the place of the future bodies of the vertebrae. This, which 

 is termed the " chorda dorsalis," is of gelatinous consistence, and is composed 

 entirely of cells ; it is inclosed in a sheath, which gradually acquires the struc- 

 ture of a fibrous membrane, and which also invests the neural axis itself ; and 

 this condition is persistent in the Amphioxus and the Myxinoid Fishes, 3 which 

 have never any other spinal column than the chorda dorsalis. The vertebrae 

 seem to be developed, in the inferior Vertebrata, in the fibrous sheath of the 

 chorda dorsalis; but in Birds and Mammals, the quadrangular plates which 

 show themselves at a very early period (Plate II. Fig. 12) appear to have an 

 independent origin. These gradually increase in number and size, so as to sur- 

 round the chorda both above and below; sending out, at the same time, pro- 

 longations from the inferior surface, to form the arches destined to inclose the 

 Spinal Cord or neural axis, which are hence termed by Prof. Owen the neural 

 arches. In this primitive condition, the body and arches of each vertebra are 

 formed by one piece on each side ; and these, becoming cartilaginous, are united 

 inferiorly by a suture, so as to inclose the chorda in a sort of case formed by 



1 The vesicula prostatica, or " uterus masculinus," has presented an unusual development 

 in some of these cases; see Prof. Weber (loc. cit.), and Prof. Theile's "Account of a Case 

 of Hypospadias," in "Muller's Archiv.," 1847. 



2 On the subject of Hermaphrodism, see Prof. Simpson's Article in the " Cyclop, of 

 Anat. and Phys.," vol. ii. 



3 "Princ. of Phys., Gen. and Comp.," \\ 321 a, 322, and 322 a, Am, Ed. 



