712 HANDBOOK OF PHYSIOLOGY. 



which is permanent in Reptiles, Birds, and some of the lower Mammalia. 

 In the hum an foatus, however, the intestinal portion of the cloaca is cut 

 off from that which belongs to the urinary and generative organs; a sepa- 

 rate passage or canal to the exterior of the body, belonging to these 

 parts, being called the sinus urogenitalis. Subsequently, this canal is 

 divided, by a process of division extending from before backwards or 

 from above downwards, into a 'pars urinaria ' and a 'pars genitalis/ 

 The former, continuous with urachus, is converted into the urinary 

 bladder. 



The Fallopian tubes, the uterus, and the vagina are developed from 

 the Mullerian ducts (Fig. 498, m and Fig. 501) whose first appearance 

 has been already described. The two Mullerian ducts are united below 

 into a single cord, called the genital cord, and from this are developed 

 the vagina, as well as the cervix and the lower portion of the body of 

 the uterus ; while the ununited portion of the duct on each side forms 

 the upper part of the uterus, and the Fallopian tube. In certain cases of 

 arrested or abnormal development, these portions of the Mullerian ducts 

 may not become fused together at their lower extremities, and there is 

 left a cleft or horned condition of the upper part of the uterus resem- 

 bling a condition which is permanent in certain of the lower animals. 



In the male, the Mullerian ducts have no special function, and are 

 but slightly developed. The hydatid or Morgagni is the remnant of the 

 upper part of the Mullerian duct. The small prostatic pouch, uterus 

 masculinus or sinus pocularis, forms the atrophied remnant of the dis- 

 tal end of the genital cord, and is, of course, therefore, the homologue, 

 in the male, of the vagina and uterus in the female. 



The external parts of generation are at first the same in both sexes. 

 The opening of the genito-urinary apparatus is, in both sexes, bounded 

 by two folds of skin, whilst in front of it there is formed a penis-like 

 body surmounted by a glans, and cleft or furrowed along its under sur- 

 face. The borders of the furrows diverge posteriorly, running at the 

 sides of the genito-urinary orifice internally to the cutaneous folds just 

 mentioned (see Figs. 499-502). In the female, this body becoming re- 

 tracted, forms the clitoris, and the margins of the furrow on its under 

 surface are converted into the nymphae, or labia minora, the labia ma- 

 jora pudenda3 being constituted by the great cutaneous folds. In the 

 male foetus, the margins of the furrow at the under surface of the penis 

 unite at about the fourteenth week, and form that part of the urethra 

 which is included in the penis. The large cutaneous folds form the 

 scrotum, and later (in the eighth month of development), receive the 

 testicles, which descend into them from the abdominal cavity. Some- 

 times the urethra is not closed, and the deformity called hypospadias 

 then results. The appearance of hermaphroditism may, in these cases, 

 be increased by the retention of the testes within the abdomen. 



