CHAPTER Y. 



METHODS OF INVESTIGATION. 



The practical result of a particular method of feeding 

 shows itself, if we neglect for the moment the production 

 of milk and wool, in a gain of flesh or fat in the body of 

 the animal and in the production of work. We have, 

 then, to consider more minutely the various circumstances 

 which are favorable or unfavorable to the production of 

 fat or flesh, and by which a greater or less amoimt of use- 

 ful exertion is made possible to the animal. 



But before so doing, it will be profitable to cast a brief 

 glance upon the methods used in investigations on these 

 subjects — on the ways and means by whoso help our 

 knowledge, especially of the laws of flesh-production, has 

 of late been essentially increased and made clearer. 



§ 1. DeTERMIKATIOK of DiaBSTIBXLITY. 



Digestion Experiments.— While the pure nutrients 

 are theoretically capable of being wholly dissolved and re- 

 sorbed in the digestive apparatus, yet in practice they are 

 so enclosed in or impregnated by indigestible matters, 

 which protect them from the action of the digestive flu- 

 ids, or the effect of the latter is so modified by the pres- 

 ence of several nutrients at once, that a greater or less 

 portion escapes digestion and is excreted in the dung. 



To determine the digestibility of a feeding-stuff, both 

 the latter and the dung of the animal are carefully weighed, 



