THE SENSE-ORGANS 475 



All of the above types of tactile corpuscles occur in man 

 and other mammals with the exception of Grandry's corpuscles, 

 which are found only in the beaks of various birds. They do 

 not seem to occur over the general hair-covered surface, but 

 are found, often in association with one another, upon such 

 modified hairless surfaces as the palms and soles, the tips of 

 the digits, the lips, the nipples, the external genitals, and, in 

 many mammals, on the end of the nose or snout. The Pacinian 

 corpuscles also occur in such various internal organs as the 

 pancreas, the submandibular gland, and, in the cat, even in the 

 mesentery. This internal distribution has led to doubt con- 

 cerning the function of these corpuscles as tactile organs, but, 

 on the other hand, their profuse occurrence and large size in 

 such places as the balls of fingers and toes can be accounted 

 for in no other way. 



The sense of taste, which in popular estimation is raised to 

 the value of one of the special senses, is, all things considered, 

 but little more than a tactile sensation, and the organs in which 

 it is located are but little differentiated from certain of the 

 foregoing. The organs of taste themselves, cut off from all 

 association with the sense of smell, are restricted in function 

 to the perception of certain elementary qualities of liquid 

 substances, as sweet, sour, bitter, and salt, qualities which are 

 mechanical or chemical in their action and, as such, can be also 

 perceived and, in part, distinguished, by the general tactile 

 sense. To prove this last it is only necessary to bring some 

 acid or astringent liquid in contact with a surface from which 

 the external layer of the epidermis has been removed. 



The ultimate organs of the sense of taste, the taste-buds or 

 taste-beakers, are found, from the amphibians on, only within 

 the cavity of the mouth, especially upon the tongue and palate ; 

 but in fishes they are far more general in their distribution, 

 and have been found in some species (e.g., bull-heads) scat- 

 tered over the skin of the external surface. Such fishes are 

 thus probably enabled to taste the water through which they 

 pass. A taste-bud consists of a group of long, spindle-shaped 

 cells, surrounded by a rampart of supporting cells of shape 



