134 The Ottawa Naturalist. [September 



formula C^, H,^^ Og, whilst that of protein is indicated by the 

 formula C,o Hm Njg SOgo, and that of carbohydrates by 

 Cj5^ H , .1 Og. From a comparison of these formulae it is evident 

 that in fats the ratio of the carbon and hydrogen (taken together) to 

 the oxygen is greater than in the protein and carbohydrates. Now 

 you are aware that the heat in the body is produced by combustion, 

 and as carbon and hydrogen are the only two combustible sub- 

 stances in these compounds (with the exception of a small amount 

 of sulphur in proteins), that class of compounds in which these 

 two elements (not already combined with oxygen) predominate 

 must necessarily be the greater heat producer. Rubner has very 

 carefully estimated the relative heat value of fat, carbohydrates and 

 protein with the follow^ing results : — 



roo grammes of fat are equivalent to 211 grammes of protein, 

 to 132 grammes of starch, to 234 grammes of cane sugar and to 

 256 grammes of grape sugar. 



Besides being used as tuel to keep up the body temperature 

 and produce energy, tats are stored up in the body as fat. 



Perceiving that fats are absorbed with the food and deposited 

 in the body, physiologists have asked themselves whether there 

 is a direct transposition into the ' adipose tissue without any 

 previous decomposition. Radziejewsky, Subbotin and others 

 endeavoured to solve the problem. 



Radziejewsky fed a dog with erucin, the glyceride of erucic 

 acid, but could find only small quantities of it in the tissues. 



Subbotin fed another dog with spermaceti and found none at 

 all in the fat cells, and only traces in the intestinal fats and 

 internal organs. What conclusions could he draw, if not that in 

 the case of carnivora the fat in the food does not pass directly into 

 the cells of the body ? 



These experiments were repeated by I. Munk, who fed a dog, 

 which had fasted a long time previously, with erucin and he got 

 contrary results finding a considerable amount of the neutral fat. 

 This, however, does not prove that the fat is transferred directly 

 without previous decomposition, for is it not possible that the fat 

 may be saponified and absorbed as a soap, and the neutral fat of the 

 same composition afterwards synthesized in the epithelium cells ? 

 In fact the most credited and better experimentally sustained idea 



