92 THEORY OF FEEDING. 



breathing be restricted by the impediment offered to the 

 contraction of the diaphragm. As the full action of the 

 diaphragm is demanded during health only when the power of 

 breathing is considerably taxed (forced breathing), this ques- 

 tion of undue bulk of the stomach and intestines as affecting 

 breathing, is essentially one of work. In pleurisy, the 

 breathing is chiefly abdominal, because any movement of the 

 ribs will cause pain to the inflamed membrane which lines the 

 ribs. 



As almost all the nitrogen of the broken-up nitrogenous 

 matters of the body is contained in the urine ; we can, by 

 making an analysis of that fluid, find out the disintegrating 

 effect which work has on these substances. Contrary to what 

 we might have expected, such an analysis shows that a horse, 

 under ordinary healthy conditions, excretes as much, or nearly 

 as much, nitrogen along with his urine during rest, as he does 

 when in fairly strong work. The expenditure is increased to 

 some extent during severe and continued labour, and in a 

 marked manner during extreme starvation. Work has a far 

 greater effect in reducing the bodily fat than in breaking up 

 nitrogenous tissue, the larger portion of which consists of 

 muscle (the lean of meat). Besides, no advantage is obtained, 

 from a working point of view, by increasing beyond a narrow 

 limit the quantity of nitrogenous matter in the food. On the 

 other hand, the amount of starch, sugar, and fat which the 

 animal can eat with benefit, is proportionate to the severity of 

 his work. Although horses cannot, like carnivora, digest a 

 comparatively large quantity of fat, fat is a necessary con- 

 stituent of their food, and cannot be wholly replaced by starch, 

 sugar, or nitrogenous matter without injury to the animal's 

 health. The large percentage of fat in oats and maize un- 

 doubtedly enhances the value of these grains as foods for 

 horses. 



When animals are deprived of food for a long period, there 



