July 7, 1905.] 



SCIENCE. 



9 



titative relationship between histidin, ar- 

 ginin and lysin in' the composition of liver 

 substance after phosphorus poisoning, ar- 

 ginin in particular being reduced below 

 the quantity found in the liver of the nor- 

 mal dog. This possibly suggests a specific 

 action by phosphorus on certain cell pro- 

 teids rich in arginin which are essential to 

 vitality. All forms of proteid decomposi- 

 tion follow, therefore, the pathway of 

 cleavage into amino acids. 



The cj[uestion arises, to what extent may 

 the amino bodies formed within the in- 

 testine be regenerated into proteid? It is 

 believed that the cells of the intestinal vil- 

 lus regenerate fat from fatty acid and 

 glycerin, since neutral fat alone is found 

 in the thoracic duct. But all the starch 

 fed is not regenerated into starch, nor is 

 maltose regenerated into maltose in the 

 body. Much may be burned as dextrose 

 and only a part is transformed into gly- 

 cogen. Long ago Schultzen and Nencki^ 

 stated that a certain amount of amino 

 bodies formed in digestive proteolysis was 

 absorbed and burned, and that the ab- 

 sorbed proteid itself followed the lines of 

 an enzymatic cleavage into amino bodies. 

 In the light of newer knowledge several 

 authorities have recently elaborated theo- 

 ries along similar lines. It has been point- 

 ed out by Folin^ that there is little evidence 

 of reconstruction of all the proteid in- 

 gested. He cites the experiments of 

 Nencki and Zaleski,^" which showed that 

 the portal blood during digestion contains 

 four times as much ammonia as arterial 

 blood, and that the mucosa of both stomach 

 and intestine yield large quantities of am- 

 monia. The inference is that the ammonia 

 of the portal vein is derived from ammonia 



' Schultzen and Nencki, Zeitschrift fur Biologic, 

 1872, Bd. 8, p. 124. 



® Folin, American Journal of Physiology, 1905, 

 Vol. 13, p. 117. 



" Nencki and Zaleski, Zeitschrift fiir physio- 

 logische Chem., 1901, Bd. 33, p. 206. 



produced in the mucosa as well as from that 

 which normally originates in the intestine 

 during tryptic proteolysis. 



The existence of denitrogenizing en- 

 zymes is afforded by the example of the 

 guanase and adenase of Walter Jones,^^. 

 which respectively convert guanin into 

 xanthin and adenin into hypoxanthin with 

 the liberation of ammonia. 



Folin believes that the greater part of 

 the proteid ingested undergoes a denitro- 

 genization through the hydrolysis of the 

 amino cleavage products. Such a reaction 

 would read 



= CNH, + H,0 = COH + NH3. 



The ammonia may be converted into urea 

 within the organism, and the nitrogen free 

 rest may be converted into sugar. The 

 simplest expression of this is seen in the 

 experiment of Neuberg and Langstein,^^ 

 who found glycogen in the liver and lactic 

 acid in the urine of a rabbit following the 

 ingestion of alanin. The transformation 

 of alanin into lactic acid may be written 



CH3 • CHNH. • COOH + HoO = 



CHs- CHOH- COOH + NH3. 

 Alanin. Lactic Acid. 



The transformation of lactic acid into 

 sugar is demonstrated by the experiment 

 of A. R. Mandel,^^ who showed an increase 

 in the sugar output in diabetes after the 

 ingestion of lactic acid. 



Stiles and Lusk^* have shown that inges- 

 tion of the mixture of amino bodies pro- 

 duced from the tryptic digestion of meat 

 may yield sugar in large quantity in dia- 

 betes. 



" Jones and Winternitz, Zeitschrift fiir physio- 

 logische Chemie, 1905, Bd. 44, p. 1. 



"Neuberg and Langstein, Archiv fiir Physiol- 

 ogic, Suppl. Bd., 1903, p. 514. 



" ]\Iandel, ' Proceedings of the American Physio- 

 logical Society,' Am. Jour, of Physiol., 1905, Vol. 

 13, p. xvi. 



" Stiles and Lusk, American Journal of Physiol- 

 ogy, 1903, Vol. 9, p. 380. 



