APPENDIX TO BULLETIN NO. 80. 
J. A. HUMMEL, ASSISTANT CHEMIST. 
In order to give in a more complete manner, the method 
of carrying on a digestion trial and of making the calcu- 
Jations, a more detailed account is given in these pages. As 
was stated in the preceding part of this bulletin, the animals 
were fed the ration to be studied for a preliminary period of 
about ten days in order to accustom them to the ration. 
They were then put into the stalls, usually at eight o’clock 
a.m. and the feces and urine collected, weighed and sampled 
each day for a period of exactly four days with the exception 
of the first trial which was extended over a period of five 
days. Samples of about eight or ten pounds of feces were 
taken at eight o’clock a.m. each day for the full period. 
From these samples the total dry matter was determined 
by drying in a water bath at 70 degrees C. A composite 
sample for analysis was made of these dried portions. 
Samples of the urine were also taken at eight o’clock daily. 
The specific gravity of the urine was determined and the 
determinations of total nitrogen and the heat of combustion 
were made immediately after sampling in order to prevent 
as far as possible decomposition of the urine. 
In all of the analyses the methods adopted by the Associ- 
ation of Official Agricultural Chemists* were used. 
The heats of combustion were in every case determined 
with a bomb calorimeter. The standard or unit of measure- 
ment of the heat of combustion is the Calorie, which is the 
energy in the form of heat required to raise the temperature 
of one pound of water 4 degrees F. The Calorie is equiva- 
lent to the work of lifting one ton 1.53 feet. The following 
description of the calorimeter and the method of using is 
taken from the U. S. Dept. of Agr., office of Experiment 
Stations, Bul. 101, pp. 11-12. ‘The bomb is made of fine 
steel and is lined with platinum. It consists of a cylinder to 
* U.S. Department of Agriculturael, Division of Chemistry, Bulletin No. 46. 
