528 PRINCIPLES OF ANIMAL NUTRITION. 
of the work done as not altogether satisfactory. In a preliminary 
paper * Atwater & Rosa compute a utilization of 21 per cent. 
Inasmuch as they have not further discussed the question of the 
utilization of the food energy for work production it would seem 
premature to attempt to do so here. It may be remarked, however, 
that the figures given seem to indicate a rather low degree of effi- 
ciency for the particular form of work investigated (riding a station- 
ary bicycle). 
Wolff's Investigations. 
The horse, being par excellence the working animal, has natu- 
tally been the subject of experiments upon the relation of food to 
work. While as yet the respiration apparatus or calorimeter has 
not been applied to the study of this phase of the subject, two ex- 
tensive and important series of investigations have been made 
upon the work horse, viz., by Wolff and his associates in Hohen- 
heim and by Grandeau, LeClere, and others + in Paris, in which the 
attempt has been made to judge approximately of the equilibrium 
between food and work from the live weight and the urinary nitro- 
gen. 
Grandeau’s experiments were made for the Compagnie générale 
des Voitures in Paris, and were directed specifically toward a scientific 
investigation of the rations already in use by the company and to 
a study of the most suitable rations for the different kinds of ser- 
vice required of the horses. They were, therefore, while executed 
with the greatest care and exactness, largely “practical” in their 
aim. 
Wolff’s experiments were made at the Experiment Station at 
Hohenheim and were broader in their scope, being directed largely 
to a determination of the ratio of (digested) food to work. The 
following paragraphs are devoted chiefly to an outline of Wolff’s 
experiments, but with more or less reference also to Grandeau’s 
results. 
Methods.—In discussing the effects of muscular exertion on 
metabolism in Chapter VI, mention was made of the interesting 
* Phys. Rev., 9, 248; U.S. Dept. Agr., Office of Experiment Station, Bull. 
98, p. 17. 
{ L’alimentation du Cheval de Trait, Vols. I, II, III, and IV, and Annales 
de la Science Agronomique, 1892, I, p. 1; 1893, I, p. 1; and 1896, II, p. 113 
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