36 HORSE MANAGEMENT IN INDIA. 



the performance of their functions impossible." Such 

 fat, he points out, must, therefore, be regarded as a tissue 

 former, and not alone as a supplier of heat, although it 

 will serve in the latter capacity on becoming broken up. 



Waste of Tissue. Every tissue of the body has a 

 certain limited time for existence (a period which is 

 directly shortened by exercise) after which it becomes 

 broken up, and is absorbed into the blood. In order to 

 remove these effete and deleterious matters, the system 

 is provided with various excretory organs, such as the 

 lungs, kidneys, &c. During respiration, the oxygen, 

 which is absorbed from the air by the blood-vessels in 

 the air-cells of the lungs, is carried through the various 

 parts of the body, so that it may break up the effete 

 tissue by combining with its carbon to form carbonic 

 acid, which the blood, at the completion of its circuit, 

 conveys to the lungs, to be by them expelled into the 

 atmosphere. 



A small amount of carbonic acid is eliminated by the 

 skin. 



We may roughly express the oxidation of the various 

 tissues as follows : 



1. Fat + oxygen = carbon -f hydrogen + oxygen 



+ oxygen = carbonic acid + water. 



2. Starch (or sugar) -f- oxygen = carbon + water 



+ oxygen carbonic acid + water. 



3. Albumen + oxygen = carbon + hydrogen + 



nitrogen + oxygen + oxygen = carbonic 

 acid + water + degraded nitrogenous matters, 

 such as urea (C a H 4 N 2 O a ), &c. 



