THEIE LIMITS AND THEIR FALLACIES. 325 



tion of taste, as may easily be shown by many simple experi- 

 ments. One of the most simple consists in bringing almost 

 any two dissimilar metals in contact, then touching the line 

 of contact with the tongue. Thus, if a disc of zinc be laid 

 on the tongue alone, there is no taste ; the same, if a disc of 

 silver. If, however, the two be brought into contact, and 

 then the tongue be applied to the point of contact, a saline 

 taste will be experienced. 



The organ of smell admits of much variation. Thus, in 

 most aquatic animals there is no communication between the 

 olfactory and breathing organs ; the nasal chamber being 

 pervious only in front. The chief difference between the 

 olfactory apparatus of fishes and reptiles is, that in the latter 

 there is always a communication with the breathing appa- 

 ratus. In the invertebrata little is known about the organ 

 of smell ; though in many the sense is acute. The bluebottle 

 fly, for example, not only deposits her eggs on gamey meat, 

 but also upon a plant (the Stepelia hirsuta), the odour of which 

 closely resembles that of animal putrefaction. 



The mere acuteness of human smell diminishes by civili- 

 sation. Savages have the faculty in a higher degree than 

 civilised mankind. Humboldt, in his political essay on New 

 Spain, informs us that the "natives follow up their enemies ly 

 scent, and that they have distinct terms for the smell of a 

 European, a negro, and an American Indian. 



According to Sir H. Davy, every individual has a different 

 smell, and so has every road, lane, and path to dogs. The 

 Kalmucks are extraordinarily acute as to smell, sight, and 

 hearing. They scent fires and camps at long distances, and 

 have only to be near a brute to become aware of his presence 

 by smell alone. Blumenbach, the German physiologist, tes- 

 tifies to the following personal experience, illustrating his own 

 acuteness of smell. Accompanying once a London physi- 

 cian in his round, they came to a house where, on entering, 

 the German nosed a smell like that of smoked bacon. Four 



