SENSES OF SMELL AND TASTE. 575 



their psychic life is so far removed from our own in terms of 

 which we must interpret, if at all. 



The earliest form of olfactory organ appears to be a depres- 

 sion lined with special cells hx connection with a nerve, which, 

 iadeed, suggests the embryonic beginnings of the olfactory 

 organ in vertebrates, as an involution (pit) on the epithelium 

 of the head region. It would appear that we must believe that 

 in some of the lower forms of invertebrates the senses of smell 

 and taste are blended, or possibly that a perception results 

 which is totally different from anything known to us. The 

 close relation of smell and taste, even in man, will be referred 

 to presently. There are, perhaps, greater individual differences 

 in sensitiveness of the nasal organ among mankind than of any 

 other of the sense-organs. Women usually have a much keener 

 perception of odors than men. The sense of smell in the dog 

 is well known to be of extraordinary acuteness ; but there are 

 not only great differences among the various breeds of dogs, 

 but among individuals of the same breeds; and this sense is 

 being constantly improved by a process of " artiflcial selection " 

 on the part of man, owing to the institution of field trials for 

 setters and pointers, the best dogs for hunting (largely deter- 

 mined by the sense of smell) being used to breed from, to the 

 exclusion of the inferior in great part. Our own power to 

 think in terms of smell is very feeble, and in this respect the 

 dog and kindred animals probably have a world of their own 

 to no small extent. Their memory of smells is also immeasur- 

 ably better than our own. A dog has been known to detect an 

 old hat, the property of his master, that had been given away 

 two years before, as evidenced by his recovering it from a re- 

 mote place. 



The importance of smell as a guide in the selection of food, 

 in detecting the presence of prey or of enemies, etc., is very 

 obvious. By culture some persons have learned to distinguish 

 individuals by smell alone, like the dog, though to a less degree. 



TASTE. 



The tongue is provided with peculiar modifications of epi- 

 thelial cells, etc., known as papillas and taste-buds which may 

 be regarded as the end-organs of the glosso-pharyngeal and 

 lingual nerves ; though that these all, especially the taste-buds, 

 are concerned with taste alone seems more than doubtful. In 



