INTRODUCTION. | 14 
other germs of disease, the indigested portion will 
pass out as feces. The pig should be fed as much 
during the fattening period as it can digest and 
nothing more. This can be easily ascertained by 
examining the feces. The kidneys secrete the 
urine and other effete material, the result of the 
disintegration of the nitrogenous substances in 
the body; they require to be in a healthy, active 
state to perform this function, or blood poisoning 
is the result; if not blood poisoning, sufficient dis- 
turbance is caused to leave the animal liable to 
disease. The heart should be strong and vigorous 
in order to be able to propel the blood to all the 
tissues of the body to nourish them. The lungs 
should be strong, with large capacity to draw in 
oxygen and give off carbonic dioxide and other ef- 
fete materials, in this way keeping the blood pure. 
The nerves which govern all parts of the body 
should be strong and active. This is largely ac- 
complished by the kind of food we feed the animal. 
What is the animal body composed of? The 
chemical constituents of the animal body may be 
thus classified: First, albuminous substances, 
characterized by the presence of nitrogen, carbon, 
hydrogen and oxygen. Second, carbo-hydrates 
and hydro-carbons, characterized by the absence 
of nitrogen and the presence of carbon, hydrogen 
and oxygen. Third, salts and water. In order to 
keep all the tissues of the body in healthy action 
and vigor, it is necessary to see that the animal 
gets a food which contains all these elements or 
to give a mixed diet which will combine to furnish 
