228 



THE UROGENITAL SYSTEM 



of the female, while in the male they are only temporary structures. The 

 scrotum does not develop in the female, being represented only by the 

 posterior commissure of the labia majora. 



Accessory Glands. The prostate gland develops in both sexes as out- 

 growths of the urethra, both above and below the entrance of the male 

 ducts. The tubules arise at 55 mm. (C H) in five distinct groups and total 

 an average number of 63 (Lowsley, 1912). The surrounding mesencyhme 

 differentiates both white fibrous connective tissue and smooth muscle 

 fibers into which the anlages of the prostate grow. In the female the 

 homologue is rudimentary; these isolated paraurethral ducts (of Skene) 

 number at most three. 



The bulbo-urethral glands (of Cowper) arise in male embryos of 30 

 mm. (C R) as solid, paired epithelial buds from the entoderm of the uro- 

 genital sinus. The buds penetrate through the mesenchyme of the corpus 

 cavernosum urethrae, about which they enlarge. The glands branch, and, 

 at 1 20 mm. (C R), the epithelium becomes glandular. The vestibular glands 

 (of Bartholin) are the homologues in the female of the bulbo-urethral 

 glands. They appear. at the same age as the male glands, grow until 

 after puberty, and degenerate after the climacterium. 



HOMOLOGIES OF INTERNAL AND EXTERNAL GENITALIA 



Male 



Indifferent Stage 



Female 



