63 



active in the study of these problems, that provided a sufficient amount 

 of protein is supplied for physiological maintenance, i. e., to replace 

 the wear and tear of body tissue, it is immaterial which of the three 

 classes of nutrients (protein, fat, and carbohydrates) furnishes the 

 energy necessary for external muscular work performed by horses. 

 The opinion of these investigators, which is quite generally accepted, 

 has been summarized as follows by Warington: "■ 



The doctrine laid down by Wolff and his fellow workers at Hohenheim is a very- 

 simple one. He distinguishes between the food necessary to maintain the horse at 

 rest without loss of weight and the extra food which must be given when work is 

 performed, if the horse is again to be maintained, without its weight suffering loss. 

 Between the weight of digestible matter in this extra food and the quantity of work 

 accomplished there is a tolerably uniform relation. Wolff reckons that digested 

 nutritive matter equivalent to 100 grams of starch is capable of producing 85,400 kilo- 

 grammeters of work, or, expressed in English terms, 1 pound of starch digested by a 

 horse will accomplish 1,232 foot-tons of work. This is 48 per cent of the full work 

 which the starch could accomplish if burned outside the body. The result is the 

 average of many experiments with different diets. 



The horse requires for its maintenance in weight while at rest a certain daily sup- 

 ply of albuminoid substance [protein], which must never fall below a certain quan- 

 tity; but the extra food given when work is to be performed may consist indifferently 

 of any digestible combustible substance, wdiether albuminoids or not. The horse 

 keeper is thus at liberty to select from a wide range of foods, and is not obliged to 

 give a preference to those which are specially nitrogenous. It should, however, be 

 borne iu mind that w^hat has just been said applies strictly only to horses which are 

 already in good working condition. Horses which are low in condition, and must 

 gain in weight of muscle before they are fit for hard work, must, of course, receive 

 a more nitrogenous diet. 



A view very commonly held to-day is much the same and in accord 

 with the above, viz, that provided an adequate quantity of protein 

 and energ}' are available for maintenance, it is theoretically immaterial* 

 which class of nutrients furnish the energy for mus(;ular work, 

 although carbohydrates and f it are practically better suited for this 

 purpose than protein, since any great excess of the latter is costly and 

 may prove injurious to the health. In this case the term maintenance 

 is not used in its strict physiological sense, but refers to a condition 

 in which no appreciable amount of external muscular work is per- 

 formed, and in which the internal muscular work is fairly uniform 

 from day to day and the body weight practically constant. Most of 

 the experiments reported on the effect of muscular work on the 

 amount of nutrients required have had to do with external muscular 

 work. A number of these investigations are referred to below. The 

 effect of internal muscular work on food requirements has also been 

 studied, especially in recent years. The experiments of this sort are 

 referred to on page 68. 



« Jour. Bath and West of England Soc, 4. ser., 4 (1893-4), p. 188. 



