930 GENERATION. 



genitourinary system can be readily understood, after the description we have just- 

 given, by a study of Fig. 308. 



External Organs of Generation. The external organs of generation begin to be 

 developed at about the fifth week. At the inferior extremity of the body of the embryon, 

 a small, ovoid eminence appears in the median line, at the lower portion of which there 

 is a longitudinal slit, which forms the common opening of the anus and the genital and 

 urinary passages. This is the cloaca. There is soon developed, internally, a septum, 

 which separates the rectum from the vagina, the urethra of the female opening above. 

 In the male, this septum is developed between the rectum and the urethra, the gener- 

 ative and the urinary passages opening together. From this median prominence, two 

 lateral, rounded bodies make their appearance. These are developed, with the median 

 elevation, into the glans penis and corpora cavernosa of the male, or into the clitoris and 

 the labia minora of the female. In the male, these two lateral prominences unite in the 

 median line and enclose the spongy portion of the urethra. When there is a want of 

 union in the cavernous bodies in the male, we have the malformation known as hypospa- 

 dias. In the female, there is no union in the median line, and an opening remains 

 between the two labia minora. The scrotum in the male is analogous to the labia 

 majora of the female; the distinction being that the two sides of the scrotum unite 

 in the median line, while the labia majora remain permanently separated. This anal- 

 ogy is farther illustrated by the anatomy of inguinal hernia, in which the intestine 

 descends into the labia, in the female, and into the scrotum, in the male. It sometimes 

 occurs, also, that the ovaries descend, very much as the testicles pass down in the male, 

 and pass through the external abdominal ring. 



From the above description, it is easy to imagine how malformation and malposition 

 of the genital organs may occur, so that it is difficult to determine the sex of the indi- 

 vidual. We may have, in a male, absence of beard and a certain degree of development 

 of the mammary glands, with a pelvic conformation approximating, more or less, that of 

 the female ; and, on the other hand, a female may have a beard, slight mammary devel- 

 opment, and a general conformation of the body resembling that of a male. This may 

 be associated with corresponding malformations of the genital organs. We may, for 

 example, have a large development of the clitoris, descent of the ovaries, more or less 

 complete occlusion of the vagina, and union of the labia majora, so that it is difficult to 

 determine the sex from an external examination ; and opposite vices of formation may 

 occur in the male, the testicles remaining in the pelvic cavity. It is not surprising, 

 therefore, that beings have existed of undetermined sex, and many cases of this kind are 

 on record. Two cases have been reported in which, apparently, the two sexes were 

 combined. The first case was presented to the Medical Society of Vienna, by Koki- 

 tansky, in 1869. This case presented, on post-mortem examination, two ovaries with 

 their Fallopian tubes, a rudimentary uterus, a testicle, and a vas deferens containing 

 spermatozoids. This individual menstruated, had an imperfect penis, and a bifid scro- 

 tum. The sexual indifference was absolute. The second case was published by Hepp- 

 ner, in 1872. This was a child, six weeks old, which had been preserved in alcohol for 

 several years. It presented ovaries, Fallopian tubes, a uterus, and a vagina opening into 

 the urethra. There were also two bodies which were shown, upon microscopical examina- 

 tion, to be testicles, a penis with hypospadia, and a prostate ; but there were neither 

 vesiculee seminales nor vasa deferentia. 



Development of the Circulatory System. 



The blood and the blood-vessels are developed very early in the life of the ovum and 

 make their appearance nearly as soon as the primitive trace. The mode of development 

 of the first vessels differs from that of vessels formed later, as they appear de *iovo in the 

 blastodermic layers, while afterward, vessels are formed as prolongations of preexisting 



