SENSE OP TASTE I PAPILLA OF TONGUE. 395 



keep up these movements for a considerable period, as if 

 carrying on a close conversation. That the Antennae are 

 delicate organs of Touch can, therefore, be scarcely questioned. 



Sense of Taste. 



499. The sense of Taste, like that of touch, is excited by 

 the direct contact of particular substances with certain parts 

 of the body ; but it is of a much more refined nature than 

 touch, inasmuch as it communicates to us a knowledge of 

 properties which that sense would not reveal to us. All sub- 

 stances, however, do not make an impression on the organ of 

 taste. Some of them have a strong savour, others a slight 

 one, and others again are altogether insipid. The cause of 

 these differences is not understood ; but it may be remarked 

 that, in general, bodies which cannot be dissolved in water 

 have no savour ; whilst most of those which are soluble have 

 a taste more or less strong. Their solubility, in fact, seems 

 to be one of the conditions requisite for their action on the 

 organ of taste ; for when that organ is completely dry, it does 

 not receive any sensation from solid bodies brought into con- 

 tact with it, which may have the most powerful taste if re- 

 duced to a fluid form ; and there are substances known, which, 

 being perfectly insoluble in water, are insipid if applied to 

 the tongue when it is covered as usual with a watery secre- 

 tion ; but which have a strong taste when they are dissolved 

 in some other liquid, spirit of wine for instance. 



500. The sense of Taste has for its chief purpose, to direct 

 animals in their choice of food ; hence its organ is always 

 placed at the entrance to the digestive canal. In the higher 

 animals, the tongue is the principal seat of it ; but other 

 parts of the mouth are also capable of receiving the impres- 

 sions of certain savours. The mucous membrane which covers 

 the tongue is copiously supplied with blood-vessels ; and is 

 thickly set, especially upon its upper surface, and towards the 

 tip, with papillae, resembling in structure those of the skin, 

 but larger. These papillae, however, are not all sensory ; for 

 some, which are of conical form, are covered with a firm horny 

 epithelium, and their function seems to be chiefly mechanical. 

 These " conical " papillae are very strongly developed in the 

 tongues of many of the lower Mammalia, to which they impart 

 a particular roughness ; thus it is by their means that a Dog 



