RESEARCHES ON PROTEID METABOLISM, 



BY E. PFLUGER. 



IT is generally accepted at the present day, in conse- 

 quence chiefly of Voit's researches and writings, 

 that : — 



First, the energy for muscular work is afforded by the 

 consumption, not of proteids, but of carbohydrates and fats. 



Secondly, the fat in the body is formed from all three 

 classes of food-stuffs, proteids, carbohydrates and fats, taken 

 in with the diet. 



Thirdly, the proteid of the food has a twofold destiny, 

 a small part going to repair tissue-waste, and being stored 

 up as tissue or morphotic proteid, while the larger part 

 enters only into the circulating juices of the body as circu- 

 lating proteid, and is broken up within twenty-four hours 

 after its entry into the body, to give rise to a corresponding 

 amount of urea. 



The work by Pfliiger and his pupils, which is presented 

 to us in the appended papers, is directed to show that all of 

 these three statements are incorrect. We may consider, in 

 the first place, the question of the source of inttsatlar energy. 

 It was strongly maintained by Liebig that all the muscular 

 work of the body was done at the expense of the proteids, 

 the fats and carbohydrates, by their oxidation and disinte- 

 gration, merely serving for the production of heat. Experi- 

 ments however, carried out by Fick and Wislicenus, Voit 

 and others, showed that muscular exercise gave rise to no 

 increase in the amount of urea excreted, or that in some 

 cases where a trifling increase was produced, the increase, 

 or, indeed, the total amount of urea excreted, was insufficient 

 to account for the energy expended on doing the work. On 

 the other hand, it was found that muscular work gave rise to 

 a great increase in the excretion of C0 2 and in the amount 

 of oxygen absorbed, so that some carbonaceous material, 

 probably sugar, was looked upon as the chief source of 

 muscular energy. 



Argutinsky (i), who has re-examined this question, finds 



