GENERAL EEMAEKS ON THE ^ENSES. 519 



to clear mental perceptions, together with the value of past ex- 

 perience in the interpretation of our sensations. A man can 

 necessarily have positive knowledge only of his own conscious- 

 ness ; hut he infers similarity of conscious states hy likeness in 

 action and expression in his fellows. It is by an analogous 

 process and by such alone that we can draw any conclusions in 

 regard to the sensations of the lower animals. The presence of 

 structures, undoubtedly sensory, in them is fairly good evidence 

 that their sensations resemble ours when similar organs are em- 

 ployed. However, this does not absolutely follow ; and the 

 whole subject of the senses of animals incapable of articulate 

 speech is beset with great difficulties. It only remains for us to 

 set forth what is known regarding man, assuming that at 

 least much of it applies to our domestic animals. Patient 

 thoughtful observation will in time place the subject in a better 

 position. 



