64 GRAHAM LUSK 



pressed ( 1 ) by excessive oxidation, heat production, by increased evapora- 

 tion of water, and (2) by the cleavage of one-eighth of the carbon and one- 

 third of the hydrogen of protein in the form of urea. Only the smallest 

 quantity of this urea production is necessary for the maintenance of the 

 animal; it arises from the cleavage of the metabolized body protein itself. 

 The larger part is eliminated in order to yield tne carbon, hydrogen and 

 oxygen containing rest in a form suitable for respiration and not injuri- 

 ous to the body. Protein nitrogen cannot be eliminated through the 

 lungs, for nitrogen scarcely combines with blood and if liberated would 

 fill the capillaries with gas, nor can ammonia be produced for this destroys 

 the blood corpuscles." 



The greater the quantity of fat given,, the smaller is the Luxus consump- 

 tion in carnivora. Among herbivora it is usually very slight because here 

 protein is taken in conjunction with an excessive quantity of carbohydrates and 

 is almost entirely used in replacement (Wiederersatz) of the body protein neces- 

 sarily destroyed which latter is the typical (minimum) protein metabolism. 



They find that following fat ingestion the feces contain magnesium 

 and calcium soaps, as shown by Boussingault. 



The authors suggest that protein may be composed of taurin, glyco- 

 coll and a carbohydrate, a "respirations "rest," they call it. One hundred 

 grams of protein would contain: 



Taurin 6.2 gm. 



Glycocoll 79.3 gm. 



"Respirations rest" 28.3 gm. 



Taurin and glycocoll would yield 33.2 gm. of urea and 49.8 gm. of 

 carbohydrate. 



They add, "It is not possible to formulate a well-grounded hypothesis 

 concerning the formation of urea because of the present uncertainty of 

 our knowledge of the composition of protein." 



At the end of the book there is a beautiful chart showing the metabol- 

 ism of the fasting cat and giving the bile secretion as intermediary 

 metabolism. 



Max von Pettenkofer (1818-1901). Pettenkofer, who is well known 

 as the man who first raised hygiene into a science of sufficient dignity to 

 be provided with an independent laboratory of its own, was not only 

 responsible for the modern drainage system of the town of Munich, 

 which converted it from the "pestilential city of Europe" into one which 

 was extraordinarily healthful, but he also made notable contributions to 

 the physiology of nutrition. 



He noted that a child with St. Vitus' dance, who partook of an in- 

 ordinate amount of apple parings, voided a urine containing a large 

 amount of hippuric acid. This was one of the earliest discoveries of the 

 influence of food on the composition of the urine. 



