483 GENERAI, THERAPEUTIC MEASURES 



Therefore no more protein is required by a horse at light work than at 

 rest, for repair of the machine. More fuel for working* the machine is, 

 however, needed. The requirements for working horses are: For light 

 work, digestible protein, 1.0 lb.; therms, 9.8. For moderate work, di- 

 gestible protein, 1.4 lb.; therms 12.40. For heavy work, digestible 

 protein, 2.0 lbs.; therms, 16.00. 



Horses doing hard work, growing and pregnant animals, and all 

 animals supplying nitrogenous products, as wool and milk, demand more 

 nitrogen in their food. The proteids, as we have seen, constitute a large 

 proportion of the solids and fluids of the body. The protein absorbed 

 into the blood is utilized in two ways. One part is energy-forming, the 

 circulatory protein of Voit. The other is tissue-building, or the organic 

 protein of Voit. 



That part which is devoted to energy-producing is not transformed 

 into tissue but is split up (katabolized) by the cells, or enzymes within 

 the cells (chiefly of muscles), and thus produces heat or energy. 



The other part is directly built into living protoplasm. If the 

 amount of circulatory protein is deficient, then the organized protein is 

 called upon, the tissues are re bled of their substance, and the body 

 emaciates. When a larger amount of protein is contained in the blood, 

 we have a proportionately larger elimination of nitrogenous matter in the 

 urine, as equilibrium is soon established in the adult animal of constant 

 weight, so that the amount of nitrogen eliminated equals that ingested. 

 In young and growing animals a portion of the nitrogen does not reap- 

 pear in the urine, but is utilized in tissue formation. This also applies 

 to previously starving animals on being well fed. An excess of circu- 

 lating proteiHj besides being wasteful economically, is harmful in caus- 

 ing various disordered conditions, resulting in the formation of products 

 of imperfect oxidation. 



The vegetable proteids are transformed into bodies of simpler chemi- 

 cal composition in the; stomach and are there converted in part by the 

 gastric juice, but chiefly by pancreatic (trypsin), biliary and intestinal 

 ferments in the intestines, into peptone, proteoses, and possibly acid 

 and alkali and native albumin. 



The epithelial cells of the intestines possess the power to transmute 

 peptones and proteoses into amino-acids. All proteids are absorbed into 

 the blood as amino-acids. It was formerly thought that they were ab- 

 sorbed as proteoses and peptones but these are transformed in the in- 

 testinal mucous membrane into amino-acids. The amino-acids in the 

 blood serve to build up all the forms of proteid tissue peculiar to the 

 various organs needed to supply waste or growth. The remaining unused 

 portion of the amino-acids in the blood is decomposed or de-aminized in 

 the liver into nitrogenous and non-nitrogenous constituents. The nitrogen 

 escapes from the kidneys in the form of urea and the carbon molecule is 

 split up (like that of carbohydrates) by the muscles cells to form heat 

 and energy, with COj as the end product. During starvation amino- 

 acid is found in the blood and tissues and evidently it is the only avail- 

 able form in which proteids can be utilized in the body, whether in the 

 building up (^^bolisE^y M^^^gjkj^^.^^g^^^^ tissue (katabolism) . It 



