4 PHYSIOLOGY AT THE FARM. 



brane, it will be seen that the trunk of the animal body may 

 be likened distantly to a hollow pillar, the external convex 

 surface of which pillar corresponds to that part of the trunk 

 which is covered by the skin, while the interior concavity or 

 pipe of the pillar answers to that part of the trunk of the body 

 which is traversed by the alimentary canal from the mouth 

 to the fundament. Thus the substance of the pillar also cor- 

 responds to the fabric of the trunk, composed of flesh, blood, 

 bone, and the other constituents of an animal organism. Thus 

 the alimentary canal, corresponding to the pipe of a hollow 

 pillar, receives the food which enters by the mouth, and prepares 

 it, in several parts of its cavity, to yield up its nutrient material 

 to minute tubes at certain points in the substance of the trunk 

 answering to the solid portion of the pillar; while the refuse, 

 after various changes, is thrown out by the fundament at the 

 opposite end of the canal in the form of excrement. The 

 nutrient part of the food taken up from the alimentary canal, 

 after various important changes, finally passes into the blood ; 

 and the blood is the sole source from which the various solids 

 and fluids of the body are actually repaired or augmented. 

 Whatever the body loses in weight and when it is stationary 

 it loses daily a weight exactly equivalent to the weight of its 

 food it loses through the blood, with the single exception of 

 the excrement or the refuse thrown out by the fundament. But 

 even the excrement is not made up entirely of the unabsorbed 

 part of the food ; for that unabsorbed part, in its passage 

 towards the fundament, is mingled with secreted matters 

 derived from the mucous lining membrane and from the several 

 glandular organs, as the liver and sweetbread, which pour their 

 products into the intestines. Hence, even when an animal is 

 kept fasting, excrement is passed, owing to the large proportion 

 of it supplied by matters secreted from the blood. When a 

 looseness sets in, the quantity of more or less altered excrement 



