410 BIOLOGY. [BOOK vi. 



So far as taste is concerned birds seem to be very badly 

 provided. They probably swallow without tasting : for their 

 tongue, usually destitute of muscular tissue ; is dry and carti- 

 laginous. 



It is among the vertebrates that the sense of taste is de- 

 veloped, but very unequally, according to species. The rodents, 

 which feed on fruits or animal substances, have a soft tongue, 

 without appendices. Those, on the other hand, which gnaw 

 roots and barks, have on the tongue a kind of integument, 

 garnished sometimes even with denticulated scales. Certain 

 carnivorous animals, especially of the genera Ftlis and Hycena, 

 have also a tongue bestrewn with papillae conical, voluminous, and 

 covered with a horny sheath. 



In dogs, monkeys, men, the tongue is voluminous, musculous, 

 flexible. On the superior surface and on the edges the mucous 

 membrane which crosses it is made rough with dermic projections, 

 rich in nervous threads. These papillae, denominated, according 

 to their varying aspect, caliciform, fongiform, corolliform, hemi- 

 spherical, seem to have for result and for function to multiply the 

 surfaces of contact with the sapid bodies. These last act only 

 in the state of solution. Their molecules severed and in suffi- 

 cient number must put themselves into intimate contact with the 

 gustatory papillae. Sapidity has very different degrees of energy, 

 according to the substances. Water containing in solution a 

 hundredth of cane sugar is insipid, while a solution of sea salt 

 to the extent of an eight-hundredth has still savour, and it is 

 enough for a solution to contain a thousandth of sulphuro- 

 hydric acid or of sulphate of quinine to be still sapid. We can 

 always, indeed we must, view in their relations the sense of 

 taste and the sense of touch : but taste is a special tactility, less 

 gross, more varied also, for the number of savours perceptible by 

 man is extremely numerous. The division of the sensitive labour 

 is for taste more evident than for touch. It seems as if there 

 were special nervous threads for certain savours. Many sapid 

 bodias, especially salts, produce different sensations, according 



