THE WOOLLY RHINOCEROS. 251 



all the northern hemisphere, accompanied, at least in a por- 

 tion of the time, by a very general and great subsidence, 

 which laid all the lower part of our continent under water. 

 This terminated much of the life of the Pliocene, and re- 

 placed it with boreal and arctic forms, some of them, like the 

 great hairy Siberian mammoth and the woolly rhinoceros, tit 

 successors of the gigantic Miocene fauna. J. W. Dawson. 



POL'YPUS. A name given to tumors which occur in mucous 

 membranes especially, and which have been compared to cer- 

 tain zoophytes. Polypi may form on every mucous mem- 

 brane. They vary much in size, number, mode of adhesion, 

 and intimate nature. Fibrous polypi are of a dense, compact 

 texture and whitish color. They contain few vessels and do 

 not degenerate into cancer. The scirrhous or carcinomatous 

 are true cancerous tumors, painful and bleeding. 



PONS VAROLII. An eminence at the upper part of the medulla 

 oblongata, first described by Varolius. It is formed by the 

 union of the crura cerebri and crura cerebelli. 



POSTE'RIOR. Opposed to ' anterior/ which see. 



PTER'YGOID. A name given to two processes at the inferior 

 surface of the sphenoid bone, the two laminae which form 

 them having been compared to wings. 



PYLOR'IC. That which relates to the 'pylorus.' An epithet 

 given to different parts. 



PYLO'RUS. A ' gate,' a ' guardian.' The lower or right orifice 

 of the stomach is called * pylorus ' because it closes the en- 

 trance into the intestinal canal, and is furnished with a cir- 

 cular, flattened, fibro-mucous ring, which causes the total 

 closure of the stomach during digestion in that organ. It is a 

 fold of the mucous and muscular membranes of the stomach, 

 and is the ' pyloric muscle' of some authors. 



Q. 



QUADRUMA'NA. (Quatuor, ' four,' and manus, ' hand.') A name 

 employed by Blumenbach (in 1791) as an ordinal designation 

 for the monkeys, lemurs, and related types, man having 

 been isolated as the representative of a peculiar order named 

 Bimanus. The views thus expressed were for a long time 

 predominant ; but a closer study of the structure of the forms 

 indicated by those names has convinced almost all living 

 naturalists that they were erroneously separated, and the two 



