10 



SCIENCE. 



[N. S. Vol. XXII. No. 549. 



Wolf^^ finds that none of these amino 

 snbstances has any effect on the blood pres- 

 sure of animals, so far as he has examined 

 them. 



Although some proteid metabolism may 

 take place as above outlined, it is an un- 

 doubted fact that proteid may be synthe- 

 sized in the body with the formation of new 

 tissue, and also that proteids injected into 

 the blood stream, as in cases of transfusion 

 of blood serum, are rapidly destroyed and 

 the nitrogen eliminated as urea. The con- 

 ditions of proteid metabolism may, there- 

 fore, be entirely similar to those of starch 

 metabolism, (1) digestive hydrolysis, (2) 

 partial combustion of the end products, 

 and (3) possible regeneration of portions 

 of the end products into substances similar 

 to the originals, but characteristic of the 

 organism, i. e., glycogen and body proteids. 

 In the case of proteids the second or meta- 

 bolic process involves the partial passage of 

 the end products through the glucose stage. 

 The third or regenerative process is pro- 

 moted by such a proteid as casein, which 

 yields a variety of cleavage products. 



Folin^^ has discovered that a man fed 

 with creatin free food eliminates a constant 

 quantity of creatinin nitrogen in the urine 

 irrespective of the amount of nitrogen in- 

 gested with the food. Thus the urine of 

 one man contained 16.8 grams of total ni- 

 trogen with 0.58 gram of creatinin nitro- 

 gen. The same man at another time, after 

 large carbohydrate ingestion, eliminated 

 3.60 grams of total nitrogen and 0.60 gram 

 of creatinin nitrogen. Folin conceives that 

 the constancy of the creatinin and uric 

 acid output is a true index to the neces- 

 sary protoplasmic breakdown, and would 

 define the nitrogen of such destruction as 



'=Wolf, Journal of Physiology, 1905, Vol. 32, 

 p. 171. 



^^ Folin, American Journal of Physiology, 1905, 

 Vol. 13, p. 66. 



the endogenous nitrogen. To what extent, 

 if any, urea nitrogen enters into this essen- 

 tial life metabolism he is not prepared to 

 say. The same idea was expressed by 

 Burian^'^ in an article published ten days 

 later than Folin 's. Burian believes that 

 purin bases are a constant product of 

 muscle metabolism and that these are oxi- 

 dized to uric acid, a part of which is fur- 

 ther converted into urea. This process of 

 itself would evolve urea as a constant 

 product of the endogenous nitrogen metab- 

 olism. According to this newer conception 

 the cells of the body through the swing- 

 ing motion of their particles do continu- 

 ally break down their own protoplasm with 

 the production of creatinin, purin bases, 

 and perhaps other substances. These same 

 cells may also break up exogenous amino 

 radicles derived from ingested proteid or 

 circulating proteid itself. 



Neuberg and Loewi^^ have made an ob- 

 servation which is not in accord with the 

 idea that proteid metabolism normally 

 passes through the amino-acid stage. These 

 authors investigated a case of cystinuria, a 

 condition in which cystin formed from 

 proteid can not be burned, but is elimi- 

 nated in the urine. After ingesting leucin, 

 ty rosin and aspartic acid these also were 

 almost quantitatively eliminated in the pa- 

 tient's urine, although the normal organ- 

 ism burns them. Since these substances 

 were not eliminated by the patient on a 

 normal diet, the presumption is that they 

 can not be normal products of intermediary 

 proteid metabolism. .The authors find it 

 difficult to explain this according to the 

 conception of a general breakdown of pro- 

 teid into amino acids. This experiment 

 lacks confirmation. 



^' Burian, Zeitschrift fiir physiologische Chem., 

 1905, Bd. 43, p. 532. 



^* Neuberg and Loewi, Zeitschrift fiir physio- 

 logische Chemie, 1904, Bd. 43, p. 338. 



