THE SPECIAL SENSES 271 



44. The sense of smell is developed in a remarkable degree 

 in certain of the inferior animals, and is especially acute in 

 reference to the peculiar odors that characterize the different 

 animals. The lion and other carnivorous beasts scent their 

 prey from a great distance ; and the fox-hound is able to track 

 the fox through thickets and over open country for many miles ; 

 while the timid, helpless herbivora, such as the deer and sheep, 

 find in the sense of smell a means of protection against their 

 natural enemies, of whose approach they are in this manner 

 warned. By training this sense in the dog, and making it sub- 

 servient to his use, man is able to hunt with success certain shy 

 and very fleet animals, which otherwise he could but seldom 

 approach. Among men, individuals differ greatly in respect to 

 the development of this sense ; and especially in certain savage 

 tribes it is found to be extremely delicate. Humboldt states 

 that the natives of Peru can by it distinguish in the dark 

 between persons of different races. (Head Note 7.) 



sight of one whose nerve of smell is not benumbed like their own. In- 

 stead of seeking to blunt the sensibilities of this nerve, it should be a 

 study to improve it, as the most delicate and available test of air im- 

 purity far superior, under ordinary circumstances, to the tests of 

 science. In this way all ordinary atmospheric impurities may be quickly 

 detected ; and it is truly remarkable how, by a little attention, this sense 

 can be so improved as to detect instantly even slight impurities to 

 which it had before been insensible. In many houses, by the total 

 neglect of this sense, there is an ever-present family odor, produced by 

 some special kind of household impurity, and of which the inmates do 

 not seern to be aware. To those accustomed to pure air, house odors are 

 always perceptible and disagreeable. This ought to be accepted as suffi- 

 cient evidence of their unhealthful tendencies ; not perhaps of an instant 

 or violent sort, yet enough so to give rise to many sensations of slight dis- 

 comfort, and producing, when long continued, a state of the body very 

 favorable to the beginning and growth of virulent diseases." Black's 

 Ten Laws of Health. 



7. The Effects of Certain Odors. "I have not seen it anywhere laid 

 down as a general rule, but I believe it might be affirmed, that we are 

 intended to be impressed only sparingly and transiently by odor. There 

 is a provision for this in the fact that all odors are vapors or gases, or 

 otherwise volatile substances ; so that they touch but the inside of the 

 nostril, and then pass away. 



44. Sense of smell in inferior animals ? How, and in what cases Illustrated ? 



