550 ZOOLOGY SECT, xm 



straight tubules by which the secretion is carried to the ureter. 

 The ureter dilates as it enters the kidneys to form a chamber the 

 pelvis into which the straight tubules of the medulla of the 

 kidney open. The openings of the tubules^are on the summits of 

 papillae, which are the apices of a series of 'pyramidal masses into 

 which, in most cases, the substance of the kidney is incompletely 

 divided. In many Mammals, however (some Primates", the Car- 

 nivora, and Rodentia), there is no such division of the kidney 

 substance, and all the ducts open on the surface of a single papilla . 

 In other Mammals again (Ox, Bears, Seals, Cetacea) the division is 

 carried so far that the kidney is divided externally into a number 

 of distinctly separated lobules. 



The ureters in all the Theria open into a large median sac the 

 urinary bladder situated in the posterior or pelvic part of the 

 cavity of the abdomen. From this a median passage, the urethra 

 into which in the male the vasa deferentia open leads to the 

 exterior. Only in the Monotremes do the two ureters and the 

 bladder all have separate openings into the urinogenital division of 

 the cloaca. 



The testes are oval bodies, which only exceptionally retain their 

 original position in the abdominal cavity, descending in the 

 majority of Mammals through a canal the inguinal canal in the 

 posterior part of the abdominal wall to lie in the perinceum, or 

 space between the urinogenital and anal apertures, or to be 

 received into a pendulous pouch of skin the scrotum. The penis, 

 present in the males of all Mammalia, consists of two corpora 

 cavernosa, firm strands of vascular tissue attached proximally to 

 the ischia except in the Monotremes, Marsupials and some Eden- 

 tata, and a central strand, the corpus spongiosum, perforated by 

 the urethral canal and dilated at the extremity to form the glans. 

 The two vasa deferentia, continued from the epididymes, which 

 are in close relation to the testes, join the urethral canal near 

 the neck of the bladder, each having connected with it, near its 

 distal end, a sacculated reservoir the vesicula seminalis. A small 

 diverticulum of the proximal part of the iirethra the uterus 

 masculinus appears to be a remnant of the Mullerian duct. 

 Surrounding this part of the urethra is a . glandular mass the 

 prostate gland ; and the ducts of a pair of small glands Cowper's 

 glands open into the urethra near the base of the penis. 



The ovaries are compressed oval bodies which retain their 

 primary position in the abdomen, or pass backwards into its 

 posterior or pelvic part. In the Monotremes large Graafian 

 follicles project on the surface of the ovary, while in other Mammals 

 the Graafian follicles are very small, and the surface of the ovary 

 almost smooth. 



The oviducts have dilated funnel-like abdominal openings, the 

 edges of which, except in the Monotremes, are fimbriated or 



