MAINTENANCE REQUIREMENTS OF MATTER 343 



TABLE 63 . ALKALI RATIO OF ASH 



434. Balancing of ash ingredients in the ration. While 

 the animal body has a considerable degree of adaptability to 

 variations in the ash supply, and while, during short periods, 

 relatively large errors in this respect may be compensated for 

 out of the comparatively large stock of ash in the body, never- 

 theless, it is clear from previous paragraphs that in the long 

 run a reasonably close balance of the ash ingredients in the 

 ration is necessary, and tables like that of the Appendix have 

 been computed as guides for this purpose. That they convey 

 useful information cannot be denied, but any attempt to base 

 actual estimates regarding ash maintenance or the ash balance 

 on such data overlooks some important considerations. 



Ash not entirely digestible. It must be remembered that not 

 all of the ash ingredients of the feed can be assumed to be di- 

 gested and resorbed-. It is true that much of the ash found in 

 the feces has really been digested and excreted again in the 

 lower intestines but this is by no means true of the entire quan- 

 tity. In the case of herbivora, especially, a considerable share 

 of the dry matter of the feed escapes digestion and it can hardly 

 be doubted that it carries with it into the feces more or less of 

 its ash elements. This is particularly true of the sulphur and 

 phosphorus of the proteins and the nucleoproteins. So far as 

 these escape digestion, they carry their organic sulphur and 

 phosphorus with them into the feces without giving it oppor- 

 tunity to contribute to acid production in the body. How far 

 the same thing is true of the other ash elements it is impossible 



