AN ESSAY UN FAT AND MUSCLE. 601 
in order to convert the carbon into carbonic acid 131bs. 3£oz. of 
oxygen, and the milch cow 11 lbs. lOf oz. in the same time. 
In whatever way carbon may combine with oxygen, the act of 
combination cannot take place without the disengagement of heat. 
There exists in the living body no other known source of heat but 
the chemical action between the elements of the food and the 
oxygen of the atmosphere, and it signifies nothing what interme- 
diate changes the food undergoes in becoming assimilated to organ- 
ised tissues, or in its passage through the liver in the formation of 
bile. The last change is uniformly the combustion of the carbon 
and hydrogen, and the production of carbonic acid, watery vapour, 
and animal heat. No part of the oxygen taken into the system is 
given out again in any other form than that of a compound of 
carbon and hydrogen ; and as these substances are supplied in the 
food, it is clear that the amount of nourishment required for any 
animal will be proportionate to the quantity of oxygen taken into 
the system. 
There are two causes which chiefly contribute to increase the 
consumption of oxygen gas ; these are TEMPERATURE and EX- 
ERCISE. We will proceed to consider the effect of these in the 
living organism by a few examples from the farmer’s every-day 
practice. In the winter the air is more condensed than in the 
summer, consequently the same volume of air in the winter con- 
tains a larger per centage of oxygen than in warm weather, when 
it is more rarified. It is for this reason that a larger supply of 
food is consumed by persons living in cold countries than by those 
who are inhabitants of hot climates. We thus perceive an ex- 
planation of the apparently anomalous habits of different nations. 
The maccaroni of the Italian and the train-oil of the Greenlanders 
are not adventitious freaks of taste, but necessary articles fitted to 
administer to their comforts in the different climates in which they 
have been born. 
Example No. 1. — A flock of Leicester sheep on tolerably good 
food will increase in weight throughout the year about 52 lbs. of 
mutton for each sheep, but this accumulation takes place chiefly 
during the spring and summer months, for, during the cold weather, 
it requires all the farmer’s supplies of food to keep them at the 
same weight. Should the cold prove very intense, and the sup- 
plies of carbon and hydrogen in the form of food be not at hand, 
the store of fat which the animals have been accumulating in the 
mild seasons will be soon made use of to keep up the animal 
temperature. 
Example No. 2. — “ One hundred sheep were folded by divisions 
of pens, each of which was 22 feet in length by 10 feet in breadth, 
and possessed a covered shed attached to it. They were kept there 
