328 ANATOMY AND PHYSIOLOGY 



tion of weight). The faculty of stereognosis depends upon the 

 exercise of muscle sense (it is the recognition of articles by hand- 

 ling them, thus awakening memories of objects previously known) . 

 Simple contact evokes no sensation without a certain degree of 

 pressure; touch and pressure are therefore closely related; with 

 increased pressure comes the impression of weight. If pressure 

 is sufficiently increased, pain will be felt, which 

 is due to the disturbance of nerves more deeply 

 situated. 



Again, a touch imparts also a sensation of 

 place, the place where it occurs; therefore the 

 sense of touch includes the place sense. 



THE SENSE OF TASTE 



F \ G 2 8 _ The tongue is spoken of as the organ of taste, 

 TASTE-BUD FROM since it bears the taste buds. The sense of taste 



ClRCUMVALLATE , .,..., 



PAPILLA OF A CHILD. ma y De regarded as a specialization of the sense 

 The oval struc- of touch and the two mechanisms somewhat 



ture is limited to the rpcP rnhlA 



epithelium (e) lining reS6I] 



the furrow, en- The nerve endings (belonging to the 5th 



upon the adjacent an< ^ 9 tn cranial nerves) which are developed 



connective tissue f or this purpose are scattered over the surface 



(f); o, taste-pore 



through which the of the tongue, and in (certain of) the papillae, 



- also in the P alate and palatine arches (possibly 



cous surface. sometimes in the pharynx). They are found in 



(A ]lcY ilPY^OL ) 



small oval bodies called taste buds, which are in 

 direct connection with the gustatory nerves. 



In order to excite the nerves of taste, substances must be either 

 already in solution or soluble by the saliva; a perfectly dry sub- 

 stance may be felt by the tongue, and its temperature, etc., will be 

 appreciated, but it cannot be tasted. Although all flavors may 

 be recognized in all parts of the tongue, some are more keenly 

 appreciated in one portion than another; for example: the bitter 

 flavors are more plainly tasted in the posterior region, while per- 

 ception of sweets is more marked in the anterior parts. The borders 

 seem to apprehend acids more quickly than the dorsum. 



Touch, temperature, and smell are all associated with taste. 

 If a substance is too hot the sense of taste is overcome by the 



