Animal Morphology. 12? 



with certain conditions of the surface of the ground, or sub- 

 stratum, beneath which special conditions are so far changing 

 every few yards in continuous succession that, though they 

 are totally unrecognized by us, yet, that to these winged 

 tribes, they give distinct sensations in the act of respira- 

 tion, which, reaching the sensorium, are there registered ; 

 and, when the desire for return arrives, then, one by one, the 

 past order of sensations becomes only sufficiently intense to 

 be agreeable to the creatures feeling, when they are return- 

 ing within a given range from the point from whence they 

 were first received. 



This view makes sensation in its general principles, or 

 binary product, a self-instructor by principles of contrast and 

 comparison. 



It will be said there are eight, and not seven, senses, and 

 that previously it had been said that there was a decided ob- 

 jection to needlessly increasing the number ; to which reply 

 is made, that it is more than probable that there are only 

 seven senses in any one body or being. The sense of smell 

 is particularly deficient in most birds, especially such as 

 arrive in fixed localities after travelling very long dis- 

 tances, as is the case with the cuckoo, the swallow, and 

 the passenger pigeon. 



The observations of any one individual are totally insuffi- 

 cient to settle a matter like the present, but the general 

 notion entertained about the senses is this that the Telluric 

 or the atmospheric sense (for such a name may stand for the 

 travelling sense), and the sense of smell, are mutually com- 

 pensating senses, or where one is, there the other is absent, 

 or for all practical purposes may be counted as absent. In 

 man, for instance, it is so for a non-active sense for locality, 

 that it may be doubted whether it has ever shown itself, 

 saving here and there in some blind man, as Metcalf, unless 

 perchance it is unduly exalted in asthmatics, when it is the 



