172 CLASS REPTILIA. 



vertebrata. Like the mainmifera and birds, they have five 

 senses ; while in fish, that of smell seems more than doubt- 

 ful ; and as we descend among the inferior animals, we find 

 sight, or hearing, or taste, reduced to a nullity, until at last 

 we find the scope of sensibility limited to a simple faculty of 

 touch. 



However, though the saurians have all their senses, yet, 

 with the exception of that of sight, they are all feeble in 

 comparison to those of mammalia and birds. Their percep- 

 tion of impressions must consequently be much more limited, 

 their internal emotions less strong and less frequent, their 

 want of communication with the external world less urgently 

 renewed, and less completely satisfied ; their feelings colder, 

 their apathy more remarkable, their instinct ill determined, 

 and their volitions ill decided ; and such, in fact, are the 

 general characteristic of these numerous animals. 



It is to this union of causes, under the immediate depend- 

 ance of a principal one, that we must connect a fact, which 

 we have already noticed in our observations on the class ; 

 namely, that among the animals of which we are writing, the 

 muscular irritability is energetic, out of all proportion with 

 the small developement of sensibility, with the little delicacy 

 of most of the senses, and with the relative smallness of 

 volume in the brain. The weakness of the senses which 

 characterizes these animals sufiices, in all probability, to 

 produce such changes in their internal organization, as may 

 cause the decrease of swiftness, of sensibility, and of internal 

 heat observable in the descent from one genus to another. 



If to such considerations we unite that of the small abun- 

 dance of blood in reptiles, the long time which it takes in 

 circulation, without passing through the lungs^ which, more- 

 over, according to some anatomists, receive no other blood 

 than what is necessary to their support, and may be opened, 

 cut, and lacerated, without producing immediate death, we 



