METABOLISM 187 



The carbohydrates seem, however, to have a specific, function 

 in relation to the katabolism of fats. When the body is com- 

 pelled to draw its energy supply chiefly from the fats, as in 

 fasting or in diabetes (in which the power of katabolizing car- 

 bohydrates is lost), or when carbohydrates are absent from the 

 diet, the katabolism of the fats fails to be complete and con- 

 siderable amounts of beta-oxybutyric acid as well as the ab- 

 normal katabolic product aceton are excreted unoxidized in the 

 urine. 



267. Non-nitrogenous nutrients in general. While it thus 

 appears that both the fats (or lipoids) and carbohydrates may 

 serve special purposes in the body, it is, nevertheless, clear 

 that their chief function is to supply energy. Their amounts in 

 ordinary rations are so abundant that as compared with their 

 functions as carriers of energy any specific purposes which 

 they serve in the body are amply provided for. As related to 

 the nutrition of farm animals in particular, it is of special 

 interest to note that not only the fats and carbohydrates di- 

 gested as such but also the products of the bacterial fermenta- 

 tion of the insoluble carbohydrates are available as sources of 

 energy. 



268. Functions of ash ingredients. While the non-nitroge- 

 nous organic nutrients serve chiefly as carriers of energy and 

 only in a minor degree to provide the compounds necessary for 

 the performance of specific bodily functions, the so-called ash 

 ingredients represent the other extreme in this respect. They 

 introduce practically no available energy into the organism but, 

 on the other hand, they are not only essential structural com- 

 ponents of the body tissues but likewise supply and maintain 

 certain conditions indispensable to the performance of the 

 bodily functions. 



The structural importance of the ash ingredients is most 

 manifest in the case of the skeleton, which, in the higher ani- 

 mals, contains relatively large amounts of calcium and phos- 

 phoric acid and small quantities of magnesium, sodium and 

 carbonic acid (81) which impart to it certain necessary me- 

 chanical qualities of strength and rigidity. The necessity for 

 a supply of these substances in the feed, especially in that of 

 growing animals, is too obvious to require discussion. The 

 ash ingredients, however, have other equally important functions 



