Feb., 1912. Mammals of Illinois and Wisconsin — Cory. 



Plan of inferior surface of niultilobed 

 liver of a mammal. (From Flower and 

 Lydekker.) 



inches in length and sHghtly more in breadth, and extending from it 

 is what is known as the vermiform appendix, a narrow worm-like 

 tube which is, so far as known, found only in Man, the higher Apes 

 and the Wombat. 

 The Liver — This organ is situated on the right side of the abdominal 

 cavit}', and is usually divided into a right and left half, being again 



subdivided by deep clefts into lobes 

 in different mammals. As a rule, 

 these divisions are more numerous in 

 carnivorous animals than in vege- 

 table feeders. The gall bladder is 

 present in some species and absent 

 in others. 

 Urinary Organs — The kidneys in most 

 mammals are compact, oval-shaped 

 organs, having a depression at the 

 border where the ducts enter ; but in 

 a few cases they are lobate, as in the 

 Whales, Seals, Bears, some of the Ungulates, and a few others. 

 They are situated in the back part of the abdominal cavity behind 

 the peritoneum and opposite the upper lumbar vertebrae, and as a 

 rule one of them lies in a more advanced position than the other. 

 The ureters connect the kidneys with the urinary bladder and open 

 directly into it in the higher Mammalia, but lower down into the 

 urino-genital passage in the lower members of the class. 

 Reproductive Organs — Lengthy discussion of this group of organs is 

 unnecessary here, and will be confined to a few general statements 

 concerning them. 



In all mammals a penis is present and almost always completely 

 developed in the male. In the Fera?, Glires, Insectivora, Chiroptera, 

 and all except a few of the higher Primates, an os penis is present, 

 but is lacking in the other orders. The testes of the male in the 

 majorit}' of cases pass out of the abdominal cavity cither periodically 

 (as in Insectivora, Chiroptera and Glires), or permanently, as in 

 most other mammals, and in the latter case, are suspended in a 

 pouch or scrotum. In the Marsupials the testes are suspended in 

 front of the penis. 



In the Whales, Seals, Elephants, Monotremes, most of the 

 Edentates, and several others, they retain their internal position 

 throughout life. 



In all mammals, except the Monotremes and most of the Mar- 

 supials, a placenta is formed by a union of the alantois with the 



