A HISTOKY OF METABOLISM 49 



respiration, and we see that the wisdom of the Creator has added to all the 

 foods the remainder of the carbon in the form of sugar, starch, etc., which is 

 necessary for the renewal and maintenance of animal heat and for the conversion 

 of inspired oxygen into carbonic acid. If these substances had not been present 

 in the food and there had been the same intake of oxygen, then the materials 

 of the animal's own body would have been used instead. 



Liebig says that only a small fraction of the bile is unabsorbed and 

 cannot contribute greatly to the formation of the feces. 

 As to the formation of fat, Liebig argues as follows: 



A spider, fierce with hunger, sucks the blood of the first fly, but is not to 

 be' disturbed by a second or third fly. A cat eats the first and perhaps a second 

 mouse, and will kill but not eat a third. Lions and tigers react the same way, 

 driven by hunger to devour their prey. 



How different with a sheep and a cow in the pasture, which eat almost 

 without intermission as long as the sun in the heavens shines upon them. 



The herbivorous animals eat in such excess that the ingestion of starch is 

 greater than is necessary for union with oxygen, and hence the animals fatten 

 through conversion of starch into fat. 



Concerning alcohol, he makes the following comments: "Alcohol is 

 oxidized in the body, the carbon dioxid elimination decreases after alcohol 

 (Vierordt) because relatively more oxygen unites with hydrogen." 



Liebig has been informed that in England all servants are given beer, 

 or where the Temperance Society is influential the money equivalent of 

 beer. Under the latter conditions more bread is eaten, so that the beer 

 is paid for twice, once in money and once in extra food containing the 

 same carbon and hydrogen equivalents as the beer. 



Liebig enters into the calculation of the oxidation of various foods 

 in the body and gives the following values (p. 106) : 



100 Liters of O 2 And they warm liters of 

 combine with water from to 37 



120.2 gm. starch 28.356 



48.8 em. fat 27.647 



Liebig also calculates the caloric value of meat. He prepares a table 

 of isodynamic equivalents which are given below, contrasted with the 

 values given by Rubner (d) later in 1885 (p. 75). 



Liebig writes: 



Since the capacity of these substances (the respiratory materials) to develop 

 heat through union with oxygen is dependent on the amount of combustible 

 elements which equal weights contain, and since the amount of oxygen neces- 

 sary for their combustion increases in the same proportion, therefore it is pos- 

 sible to calculate approximately their relative heat producing power or respira- 

 tory value. The following table contains the respiratory materials arranged in 

 one possible order. The figures express the relative amount of each substance 

 which a given amount of oxygen would convert into carbonic acid and water or 



