550 NUTRITION OF FARM ANIMALS 



method of comparison in the case of the animal as well as being 

 the most convenient in practice. 



651. Analysis of total work. A quadruped performs work 

 by means of locomotion, with or without draft, either horizon- 

 tally or on an inclined plane. The work which it performs 

 may therefore be subdivided into work of locomotion, work of 

 draft and work of ascent and the efficiency for each form com- 

 puted separately. The same is of course true of man, but in 

 addition other forms of work, such as turning a crank with 

 the hands or with the feet (stationary bicycle) or lifting a 

 weight directly may be performed. The method of analyzing 

 the work of a quadruped has been worked out especially by 

 Zuntz and may be conveniently illustrated from Zuntz and 

 Hagemann's investigations on the work horse. 1 The methods 

 of indirect calorimetry were used, carbon dioxid production 

 and oxygen consumption being determined with the Zuntz ap- 

 paratus (279) and the corresponding energy output calculated. 

 The work was done upon a special tread-power located in the 

 open air, and during the rest experiments the animal likewise 

 stood in the tread power. The inclination of the platform of 

 the power could be varied, and it could also be driven by a steam 

 engine, so that by setting it horizontal the work performed by 

 the animal was reduced to that of locomotion alone. The dis- 

 tance traveled was measured by a revolution counter and in the 

 experiments on draft the animal pulled against a dynamometer. 

 The apparatus used is illustrated in Chapter VI, Fig. 33 (313). 



652. Horizontal locomotion. This is an important factor 

 in work production, since it requires the expenditure of con- 

 siderable energy in successive liftings of the body at each step 

 and the overcoming of internal resistances. The energy thus 

 expended does not ultimately produce any work in the me- 

 chanical sense, but all appears as heat. The work of locomotion, 

 therefore, is in a sense not useful work although necessarily in- 

 cident to the performance of the work. 



If the tread power be set horizontal and driven by a motor, 

 the total energy output by the subject will measure what may 

 be called, by analogy with the gross efficiency (648), the gross 

 expenditure in locomotion. Subtracting the energy output 

 during rest (standing) from the total output during locomotion 



iLandw. Jahrb., 18 (1889), i; 23 (1894), 125; 27, Ergzbd. Ill, (1898). 



