HEART, LUNGS, AND SKIN. 291 



THE HEART AND LUNGS. 



There is nothing whatever remarkable in the heart and lungs ; 

 but the blood-vessels, like those of most of the lower animals, are 

 so elastic in their coats that they quickly contract when divided, 

 and a fatal bleeding rarely results. 



THE SKIN. 



The skin of the dog is said to be quite free from perspiration, 

 but this is a mistake, as I have often seen the short hairs of a 

 smooth-coated dog glistening with fine beads of liquid, poured 

 out on a hot day, when strong exercise was taken. The tongue, 

 however, is the grand means of carrying off heat by evaporation, 

 and its extensive surface, when hanging out of the mouth, is suf- 

 ficient for the purpose, as the fluid is carried off more rapidly 

 from the air passing over it in expiration. I am persuaded that a 

 considerable amount of insensible perspiration is constantly going 

 on from the surface of the skin, and that nothing ought to be done 

 which is likely to check it. This, however, is contrary to the 

 generally received opinion, which is that nothing of the kind 

 takes place in this animal. 



