MILK PRODUCTION AND BODY INCREASE OF DAIRY COWS 7 
composite was one-twentieth of the total, and was preserved by the 
addition of chloroform to the storage bottle. The feces were weighed, 
immediately dumped on a large zinc-covered mixing board, mixed 
quickly, quartered, and sampled, the sample being placed in covered 
cans which were taken to the laboratory for the preparation of the 
composite samples. These composite samples were made up of one- 
fortieth of the total feces, and were kept in duplicate in covered zinc 
cans of about 3 liters capacity. The lid was made air-tight by a 
broad rubber band over the crack, and a few drops of carbon bisul- 
phide were added from time to time as a preservative. 
WEIGHING AND SAMPLING MILK 
The milk, after weighing, was well mixed by pouring from one 
bucket to another. A sample was preserved by the addition of 1 
cubic centimeter of 40 per cent formalin per liter. 
The morning milk was combined with the evening milk in the pro- 
portion of their respective weights to form the daily sample. From 
these daily samples the aliquots for the composites were weighed out, 
one twenty-fifth of the total being so preserved. The composite 
samples were weighed out in duplicate. A separate portion of each 
of the daily milk samples was kept for nitrogen estimations. All 
weights of urine, feces, and milk were taken on scales weighing ac- 
curately to within 5 grams. The aliquots were weighed on balances 
accurate to within 0.01 gram. 
THE RESPIRATION CALORIMETER 
Apparatus. — The respiration calorimeter, as its name implies, is an 
apparatus for the measurement of the animal respiratory products 
and the heat emission. This particular apparatus is an open-circuit 
Atwater and Rosa respiration calorimeter modified so as to be suit- 
able for work with cattle instead of men. A detailed description of 
its construction and operation has been published by Atwater and 
Benedict (l) 2 and by Armsby (2). It consists of a copper-lined cham- 
ber containing a comfortable stall large enough for a medium-sized 
cow, the animal being able to lie down or stand at will. 
Gases. — -The doors close tight against rubber gaskets and the ven- 
tilation is maintained by means of a pump which draws a constant 
current of air through the chamber and measures the volume at the 
same time. This ventilating air current is sampled and analyzed as 
it enters and leaves the chamber and in this way the gases added by 
the animal are determined. 
Heat. — The heat removal and measurement are accomplished by 
means of a current of cold water circulating through a coil of copper 
tubing within the chamber. In this experiment the gas and heat 
measurement covered 24 hours, subdivided into two 12-hour periods. 
Calorimeter period. — The cow was placed in the calorimeter cham- 
ber at about 1 p. m. At 6 p. m. the experiment began, ending the 
second day following at 6 p. m. While the animal was in the respira- 
tion calorimeter no attempt was made to keep the urine and feces 
separate, and the total excreta were weighed and sampled at the end 
of each 24 hours. 
* Figures in italics in parenthesis refer to Literature Cited, page 33. 
