Page:Popular Science Monthly Volume 65.djvu/190

186 experiments, and by the combustion of alcohol in a specially devised lamp.

As indicating the character of the work carried on by Professor Atwater with this apparatus, a recent experiment may be cited. In this the subject remained in the respiration chamber for thirteen consecutive days, making the experiment the longest one on record and in many respects the most

complete. There were three days of work on a so-called sugar diet, three days on a fat diet, one day of hard work on a fat diet, two days of fasting, and four days on a light and very simple diet, the subject sleeping or lying down during one day, sitting up one day, and two days doing light work on a bicycle provided with an ergometer for measuring the work. The observations were unusually complete, including in addition to the carbon, hydrogen and heat, the oxygen and the income and outgo of sulphur and phosphorus. A record of the body weight was also made by a new method in which the subject was weighed from the outside.

The adaptation of the respiration calorimeter to use with farm animals marks a decided advancement in the method and facilities for studying the fundamental principles of animal nutrition. This has been accomplished by Dr. H. P. Armsby and J. A. Fries, who, working in cooperation with the Bureau of Animal Industry of the Department of Agriculture, have constructed an apparatus of this type at the Pennsylvania Experiment Station. In adapting the apparatus to experiments with large animals, it was necessary not only to increase the size of the respiration chamber, but to introduce a considerable number of special features so that the operations of feeding, weighing, collecting the excreta, etc., could be performed entirely from without. Among the most interesting of these are the devices for weighing the heat absorbers from the outside, the air lock for introducing feed and water without allowing the escape of air from the respiration chamber, and similar devices for the collection of the liquid and solid excretory products.

By check experiments the apparatus has been found to be very accurate, the measured heat being practically identical with the theoretical amount produced by burning alcohol in the respiration chamber. In ordinary