THE HEART AND LUNGS--THE SKIN, 351 
partially so, The bowels are extremely liable to become costive, 
which is in great measure owing to the want of proper exercise, 
and this also is very apt to produce torpidity of the liver. It may, 
however, be observed that in almost all particulars, except the 
tendency to vomit, the digestive organs of the dog resemble those 
of man. 
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, how- 
ever, is the grand means of carrying off heat by evaporation, and 
its extensive surface, when hanging out of the mouth, is sufficient 
for the purpose, as the fluid is carried off more rapidly from the 
air passing over it in expiration. I am persuaded that a consider- 
able 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. 
