232 



ELEMENTS OF MAMMALIAN ANATOMY. 



are specially sensitive regions. The nerves terminate 

 in a kind of wreath formation about the base of the 

 vibrissae. 



All of these sense organs are invisible to the naked 

 eye except the Pacinian corpuscles, whose function is 

 unknown. If the mesentery is held up and looked 

 through toward the light, the Pacinian corpuscles or 

 sensory nerve terminations appear as translucent oval 

 bulbs about two millimeters long. If a piece of the 



mesentery containing a corpuscle is 

 pinned tense on a piece of cork and 

 then cut out and placed ten minutes 

 in 3% acetic acid, the termination of 

 the nerve within the corpuscle may 

 be seen with a microscope magnifying 

 thirty diameters. All the spinal sen- 

 sory nerve fibers enter the cord by the 

 posterior root (Figs. 90 and 96). 



The Olfactory Organ.- -The organ of 

 smell lies in that part of the mucous 

 membrane lining the caudal part of 

 the nasal cavity and the basal third of 

 the ethmoturbinal bones (Fig. 18). 

 That part of the mucous membrane 

 containing the olfactory cells is known 

 as the Schneiderian membrane. In a fresh specimen it is 

 of a grayish color while the other mucous membrane is 

 red. The first pair of cranial nerves convey the olfactory 

 impulse to the brain. They pass through the foramina in 

 the cribriform plate of the ethmoid bone, to the olfactory 

 bulbs, from each of which two roots extend to the base 

 of the cerebrum (Fig. 90). 



The Gustatory Organ.- -The organ of taste is located 

 chiefly in the mucous membrane on the dorsum of the 



FIG. 105.-- PACINIAN 

 CORPUSCLE FROM 

 THE MESENTERY. X 

 20. 



ax, Axis-cylinder ; n, 

 neurilemma ; m, the 

 white substance of 

 Schwann; e, epithe- 

 lial cell. 



