596 



EXPERIMENT STATION RECORD. 



obtained with tlie same substances by the potassium chlorate metbod 

 shows the Ibllowinji- lehition: 



Heats of cumbu8tion by old and new methods. 



Material. 



Casein 



Egg albumen 



Ciystallizetl albiiuicn 



Fibrin 



Couglutin 



Average of all albuiniuoids 



With 

 oxygen. 



Small 

 calories. 

 5, 858. .3 

 5, 735. 2 

 5, 672. 

 5, 637. 1 

 5,479.0 



With 

 KCIO3. 



Small 

 calorics. 

 5,717 

 5,579 

 5,598 

 5,511 

 5,362 



5,711.0 



5,567 



Relation of 

 ileterinina- 

 tions by 

 two meth- 

 ods. 



97.59 



97.28 

 98.70 

 97. 7G 

 97.86 



97.48 



From the standpoint of thermodynamics the albuminoids are never 

 completely consumed in the animal body. Only in isolated cases, with 

 au absolute meat diet, for instance, is the digestion of albuminoids at 

 all complete. Generally a considerable part of the albuminoids of the 

 food passes through the body undigested. Herbivorous animals digest 

 only 50 to 80 per cent of the albuminoids, the amount varying some- 

 Avhat with the character of the food. Furthermore, when an albumi- 

 noid is digested in the animal body it never gives up all its energy, 

 but breaks np, leaving urea and other nitrogenous products uno.xidized. 

 These cleavage products, which are excreted, are laden with energy 

 which can not, however, be used to advantage by the animal organism. 

 The amount of energy of the alliuminoid which is really utilized by the 

 organism, be it little or great, is determined by the quantity and char- 

 acter of these cleavage products which are excreted. 



Let us suppose that in a given case the food consumed contains an 

 average albuminoid, with 10 per cent of nitrogen, and yielding 5,711 

 small calories, and that the total nitrogen is excreted in the form of 

 urea. One gram of albuminoid yields 0.3428 gm. of urea, 1 gm. of 

 urea yields 2,537 small calories; hence the above quantity yields 8,697 

 small calories — that is, 15,23 per cent of the energy of the albuminoid 

 is not utilized. 



In another case let the albumen be in the form of couglutin, which 

 contains 17.51 per cent of nitrogen and furnishes 5,179 small calories. 

 Under tlie same conditions as before 1 gm. of couglutin yields 0.3752 

 gm. of urea with 951.9 small calories. Therefore, 17.37 per cent of the 

 energy of the couglutin is lost to the organism. 



In very many cases, however, the cleavage of the albuminoid does 

 not progress as far as urea. A part of the nitrogen is used in forming 

 uric acid and other cleavage products. Herbivorous animals often 

 excrete a considerable part of the nitrogen as hippuric acid. It maybe 

 easily shown by thermochemical methods that only the glycocol group 

 of the hippuric acid molecule is derived from albumen. Now, 1 gm. 



