578 



COMPAEATIVB PHYSIOLOGY. 



complex data, even leaving out of account other senses, such as 

 vision.. 



The glosso-pharyngeal is the principal nerve for the hack of 

 the tongue, and for the tip the lingual ; or according to some 

 special flhers in this nerve, derived from the chord tympani. 



It is worthy of note that temperature has much to do with 

 gustatory sensations, a very low or a very high temperature 



Pig. 423.— Taste-buds from tongue of rabbit (after Bngelmann). 



being fatal to nice discrimination, and, as would he expected, a 

 temperature not far removed from " body-heat " (40° C.) is the 

 most suitable. 



A certain amount of pressure is favorable to tasting, as any 

 one may easily determine by simply allowing some solution of 

 quinine to rest on the tongue, and comparing the sensation with" 

 that resulting when the same is rubbed into the organ ; hence 

 the importance of the movemeAs of the tongue in appreciating 

 the sapid qualities of food. 



Comparative.— Among the lowest forms of life it is extremely 

 difficult to determine to what extent taste and smell exist sepa- 

 rately or at all, as we can conceive of them. The difPerentia- 

 tion between ordinary tactUe sensibility and these senses has 

 no doubt been very gradually eflPected. Observations on otu- 

 domestic animals show that their power of discrimination by 

 taste as well as by smell is very pronounced, though their likes 

 and dislikes are so different from our own in many instances. 

 At the same time we find that they often coincide, and it is not 

 unlikely that a dog's power of discriminating between a good 

 beefsteak and a poor one is quite equal if not superior to man's, 

 and certainly so if his sense of taste, as in the human subject, is 

 developed in proportion to his smelling power. 



