476 



MAMMALIA— PHYSIOLOGY 



Cutaneous Sensibility. — Besides light touch we have sense organs 

 for deep pressure sense and pain. Adjacent to each other there are 

 end organs for sensibility to cold and heat. It is said that there 

 are over 250,000 cold spots and but 30,000 warm spots. Sometimes 

 a paradoxical sensation of cold may be aroused by a hot stimulus. 

 The cheek is relatively insensitive to pain. 



^vtox- <y/Qnds 



Cochlea^ \ 



Cowi'ty of ^Ac-jy v< 



ty/nponum or drum — r^^J '"" 



- > 



Auc/ifory 

 ccfno/ 

 ancf 

 tvo//S 



—-Sty/oid pr-Qcess 



- • Internal corofid artery 



/Auditory tube 



Fig. 254. Diagram of the human ear. (After Morris. Courtesy of P. Blakiston's 



Son & Co.) 



Olfactory Sense. — Olfactory sensations are served by the nasal 

 mucous me?nbra7te which has end-organs leading to the olfactory 

 nerves. The end organs for the sense of smell are limited to the 

 upper part of the nasal cavity. The epithelial layer consists of 

 columnar supporting cells and several layers of nerve cells which 

 are elongated in shape and nucleated. The prolongation of the 

 Q^W peripherally between the columnar cells terminates at the surface 

 in from six to eight hair-like processes while the central prolongation 

 continues as a non-medullated nerve fiber to the olfactory lobe where 

 it arborizes in relation to the dendrites of certain " mitral cells " 

 whose axones transmit impulses by the olfactory fibers. 



Static Sense. — The organs of equilibration are the semicircular 

 canals of the internal ear. 



Gustatory Sense. — The organs of taste consist of sensory cells 

 found in the taste buds of certain papillae on the tongue. (See page 



