470 EXPERIMENT STATION RECORD. [Vol.37 



servations upon five indi\iduals suffering from Graves's disease showetl that the 

 amount of creatin excreted depended on the intake of protein. It was increased 

 by high protein feeding and decrea.sed by low protein feeding. 



Inhibition of digestion of proteins by adsorbed tin, B. C. Goss (Jour. Biol. 

 Chem.. SO (1917), No. 1, pp. 53-60. fig. 1). — This paper reports experiments in 

 which artificial gastric and tryptic ditcestions of proteins were carrie<l out in 

 the presence and absence of adsorbed tin. The main object was to determine 

 whether or not the .stable tin-protein complex, formed by the adsorption of tin 

 by foods having a high protein content, would pass through the body without 

 being broken up by digestion. 



It was found that " tin is readily adsorbed from solutions by coagulated 

 proteins in amounts varying with the concentration according to the adsorption 

 law of Freundiich. This adsorption takes place rapidly at first and then 

 continues to increase slowly for several days, presumably becau.=e of the time 

 required for diffusion into the solid. The adsorption complex is extremely 

 stable and does not lose tin to a dilute acid or jilkaline aqueous phase con- 

 taining no tin. altliough the percentage of tin in the solid may be as high as 

 fiO per cent. The presence of this tin. even in small amounts, interfered 

 markedly with the digestion of the protein by either peptic or tryptic digestion, 

 as was indioated by the change in color of the biuret reaction and by the 

 visible retardation of the solution of coagulated proteins." 



It appoarefl that it was only part of the protein, directly joined to the tin. 

 whose digestion was hindered. " The effect of this retardation on the food 

 value of a protein containing tin can only be a matter of conjecture, but it Is 

 probably small, since the total tin In foods rarely exceinls 0.03 per cent." 



It was found that even after two days, in the ca.se of artificial peptic 

 digestions of the tin albumin containing 32 per cent of tin, there was no tin 

 in a dialyzahle form and only a very small amount in a filterable form, the 

 latter probably bein-.: present as a colloid suspension of particles of the tin 

 protein complex, split away from the .solid by .solution of the conne<'ting 

 albumin. " In the tryptic digestions no dialyzahle tin was found in the liquor 

 and only traces of filterable tin. Moreover, during digestion the percentage 

 of tin in the solid rapidly increased, indicating that the protein which was 

 not dirwtly bound to the tin was being dissolved away." 



The insoluble complex formed when coagulated proteins are brought into con- 

 tact with solution containing tin was not broken up to any extent by artificial 

 gastric and tryptic digestions. The author states that " while it is impossible 

 to predict what the action of bacteria in the stom.ich and intestine would be, 

 it Is to be questioned whether the tin-protein complex is broken up in the 

 actual digestive processes in the body and whether the tin which is combined 

 in this way can have any toxic action." 



Effect of ing'estion of coffee, tea, and caflfein on the excretion of uric acid 

 in man, L. B. Mendei. and Emma L. Wardeli, (Jour. Amer. Med. Assoc. 68 

 (1917). No. 2.'i. pp. 1805-1807. fig. /).— The authors review the literature of the 

 physiological effect of caflfein and report the results of a study undertaken to 

 determine the effect of caflfein ingestion upon the excretion of uric acid. The 

 subject of the oxiierinient received a purin-free diet and. after the endogenous 

 level of uric acid excretion had been reached, a definite quantity of coflfee 

 infusion of known caffein content was added to the diet (»n each of five con- 

 scutive days. Experiments were also made with decaffeinated coflfee, caffein, 

 and tea. 



The authors state that a modification of Benedict's method for determining uric 

 acid made possible more accurate determinations than had hitherto been 

 obtained. 



