to the Rearing and Feeding of Cattle. 
219 
anythina: which tends to increase the amount of oxygen inspired 
will occasion a greater consumption of food. Thus exercise in- 
creases the number of our respirations and consequent supply of 
oxygen to the system, and the result is, that, after exercise, we 
consume more food than we should have done had we not re- 
ceived it. 
The only use of clothes, in the abstract, is to economise food. 
They assist in retaining the heat of the body, and render less food 
or fuel necessary for this purpose. 
In herbivorous animals the fuel used in the production of heat 
consists of sugar, starch, gum, and other ingredients of food, 
which do not contain nitrogen. 
In carnivorous animals, or those which live entirely upon flesh, 
the heat of their bodies is supported by the combustion of their 
own tissues. Hence it is that we see the hyena, pent up in the 
cage of a menagerie, move continually from one side of the den to 
the other. These movements do not arise from an impatience of 
confinement, but from the necessity of sustaining the temperature 
of its body by the combustion of its tissues. Its continued motions 
accelerate the waste of its body, and introduce more oxygen into 
its system by the increased rapidity of its respirations. 
From this rapid sketch of the functions performed bv the 
various ingredients of food, you will be enabled to understand the 
meaning of the following table, which is extracted from Professor 
Liebig's work on Animal Chemistry : — 
Elements of Nutrition . Elements of Respiration. 
, A, ^ , y< ^ 
Vegetable fibrine Fat Pectine 
„ albumen Starch Bassorine* 
„ casein Gum Wine 
Animal flesh Cane sugar Beer 
„ blood Grape sugar Spirits 
Sugar of Milk 
The elements of nutrition contain nitrogen, and are of the same 
composition as flesh, while the elements of respiration are des- 
titute of nitrogen, and unfitted for the nutrition of the animal 
frame. 
II. — In the preceding part of the lecture we have given a rapid 
sketch of some of Liebig's discoveries in Animal Nutrition. We 
cannot follow him, on an occasion like this, in his elaborate 
reasonii gs, to prove the accuracy of his views; but at the same 
time it is necessary that you should be possessed with a perfect 
confidence of their truth, otherwise you will be unwilling to 
admit the explanations which they furnish of your own practice. 
* The chemical substances called pectine and bassorine are the pure 
principles of gum and mucilage. 
