to the Rearing a?id Feeding of Cattle. 
231 
elevate it to the proper temperature of the body. This quantity 
of carbon corresponds to nearly 3 lbs. of mangold-wurzel. The 
actual loss is, however, very much greater than this, as much of 
the water is converted into vapour at a great expense of heat. 
In feeding; pigs we endeavour to avoid this loss as much as 
possible, by giving them little water and very dry food. Those 
who feed pigs are well aware of the fact, that they thrive more 
rapidly on dry than on wet food. The explanation of this fact 
has now been given. 
As muscle is formed only by the gluten or albumen of the food, 
which albumen is in reality flesh itself, we can ascertain the 
comparative value of food, as far as the production of muscle is 
concerned, by estimating the exact quantity of the nitrogenous 
constituent of the food. The following table has been con- 
structed by estimating the quantity of nitrogen in the food, and 
multiplying this by 6| ; the product is the quantity of albumen.* 
This method is far more exact than the mechanical process pro- 
posed by Sir Humphry Davy, which the progress of organic 
chemistry has shown to be insusceptible of accuracy. The ana- 
lyses used in the production of the table have been made by 
Boussingault and myself. When I found that my analysis 
differed considerably from that of Boussingault, I have taken the 
mean of both of our analyses, on the presumption that this will 
give a fairer indication of the average value of food, as the amount 
of nitrogenous matter varies, according to the state of cultivation. 
Nearly all the kinds of food analysed I have procured from Lord 
Ducie's farm at Whitfield, and they were selected as fair average 
specimens. In all cases the table is drawn out in correspondence 
with the preceding table of the quantity of water and ashes. 
When these are added to the quantity of albumen, which we find 
by analysis, and the combined number subtracted from the whole 
quantity of food, it is obvious the remainder must be the un- 
azotized part of the food : this being known, we are in possession 
of approximative, though not perfectly accurate, information 
relative to the value of the food for the support of respiration and 
production of fat :f — 
* The analyses which form the foundation of this table are given at the 
end of the lectures. 
t The second column is only intended to serve as a rough temporaiy 
approximation. Professor Liebig is engaged in examining this subject in 
detail, and will furnish a more accurate mode of determining this point. 
Azote and unazotized are synonymous terms with nitrogen and unnitro- 
genized. I have delayed giving the analyses of Swedish turnips and man- 
gold-wurzel, because I find them to vary in their value according to the 
soil in which they grow. I shall, however, publish the analyses, after a 
more extended examination. 
