368 A MANUAL OF VETERINARY PHYSIOLOGY 



In some German experiments made by Wolff on the subsist- 

 ence ration, 83 pounds of digestible dry organic material were 

 found necessary to maintain the body weight, and from this the 

 digestible fibre, i-6 pounds, was deducted, as in the experience of 

 Wolff the fibre digested by horses was of no value as sustenance 

 either at work or rest. In the writer's observations on the 

 essential diet for horses, it was found the body weight could be 

 maintained on 12 pounds of hay. 



The essential diet presupposes that the food possesses a suffi- 

 cient proportion of digestible proteins. In one of Grandeau's 

 experiments a horse received 33 pounds of wheat-straw per diem, 

 which furnished 13 pounds of digestible matter daily (nearly 

 twice the amount actually required), but this diet only supplied 

 0-157 pound of digestible proteins, or less than one-third of the 

 minimum, the result being the horse died from starvation. 



The essential diet for an ox weighing 1,000 pounds is, accord- 

 ing to the experiments of Wolff, 0-5 pound to 06 pound of 

 protein, and 7 pounds to 8 pounds of non-nitrogenous matter 

 reckoned as starch. The ratio of nitrogenous to non-nitrogenous 

 matters is as 1 : 14. According to the same authority, sheep 

 require a relatively larger essential diet, owing to the growth of 

 wool and its accompanying fat — viz., for 1,000 pounds of live 

 weight 0-9 pound of protein and 10 -8 pounds of non-nitrogenous 

 matter, the ratio being 1 : 12. 



The Fattening of Animals for Food may not be regarded as a 

 physiological process, nevertheless, the fundamental principles 

 involved are purely physiological. The whole agricultural world 

 is indebted to the life labours of the late Sir John Lawes and the 

 late Dr. Gilbert for a knowledge of the true principles of fattening. 

 We have seen how their work led to the Liebig doctrine of the 

 physiology of dietetics being overthrown. In one of the public 

 statements made by Lawes on the subject of these experiments 

 he explained the method of inquiry adopted :* 



' Writers on agricultural chemistry and physiology have generally 

 assumed that it is chiefly the proportion of the nitrogenous or so- 

 called flesh-forming substances contained in them which determines 

 the comparative value for feeding purposes of different foods. The 

 coloured diagram before you will enable you to judge whether or 

 not this supposition is justified by the practical experience of feeding. 

 This diagram has been constructed by the animals themselves. 

 They know nothing about nitrogenous or non-nitrogenous con- 

 stituents, digestible or indigestible cellulose, and so on ; but are 

 gifted with an unerring instinct which enables them, not only to 

 distinguish between substances which are and are not food, but also 

 to select from a variety of food-stuffs those which are most suitable. 

 ... In the experiments to which the diagram refers, as well as 



* ' The Chemistry of the Feeding of Animals,' a lecture delivered before 

 the Royal Dublin Society, March, 1864, by John Bennett Lawes, F.R.S. 



