ON THE VARIETIES OF VEGETABLE FOOD. 223 
comes of it? What is the result of the lapse of that period 
under such a temperature] You have produced out of that 
matter bones, sinews, nerves, heart, liver, lungs, feathers, brains, 
and claws. The whole of these are produced from the egg, and 
yet the egg itself is nothing more nor less than albumen. After 
this, gentlemen, you need not wonder that under the operation 
of the vital power nitrogenous matter should assume such great 
varieties of forms as we see it assume, not only in different 
kinds of animals, but even in the same animal. Now, gentle¬ 
men, a question arises as to how the animal heat could be pro¬ 
vided for an animal fed only on nitrogenous food, and furnished 
with none of the elements of respiration. Suppose a man to be 
compelled to eat nothing but mutton or beef] Gentlemen, we 
have this question answered by the case of carnivorous animals 
—animals which live entirely by eating other animals. How 
do these animals obtain the heat which is necessary to their 
existence] You will observe that they take an immense deal 
of exercise. In the pursuit of their prey they are obliged to ex¬ 
ercise the various muscles of their body ; and it is this motion 
of the muscles of the body which causes a consumption of those 
muscles by the air taken into the lungs, and thus keeps up the 
animal heat. In the case of the electric telegraph, you are per¬ 
haps aware that there is a zinc and copper plate, immersed in 
acid and water; and as soon as ever a communication has been 
made by wire between the two, an electric current passes along 
the wires, and at the selfsame instant the acid acts upon the zinc, 
and dissolves a portion of it, proportioned exactly to the strength 
and continuance of the electric current. In the very same way, 
gentlemen, when I stretch out my arm, the muscle which pro¬ 
duced that motion, that exercise of force, is acted upon by the 
air circulated through the arteries, and it is the oxidation or 
combustion of that muscle by the air that gives me the power 
necessary to move my arm. As soon as my will is exercised, 
and I attempt to put forth my arm, an electric communication is 
made, a portion of the muscle is insensibly consumed, and the 
proper amount of force is instantly produced. Now, we all 
know that the more a limb is exercised the more it wastes for 
the day. The muscles will be smaller at night than in the 
morning; for the period of sleep is that appointed for the in¬ 
crease of the muscles. It is well known that when parties have 
been taking a large amount of exercise, the muscles of their 
bodies are comparatively wasted. Now this waste is caused by 
the consumption of the muscles by the air which circulates 
through the arteries, and it is this consumption which provides 
animal heat when the animal can obtain none of the ordinary 
elements of respiration. You will observe how wonderful it is 
