430 SCIENCE PROGRESS 



obtained one gramme of urea nitrate from ten grammes of the 

 silver compound. 



Besides these basic bodies the number of amino- and amio- 

 acids known to result from the zymolysis of proteid has been 

 increased, aspartic and glutaminic acids and asparagin having 

 been identified. 



The occurrence of a body giving a purple colour with a few 

 drops of chlorine or bromine water was many years ago 

 described by Nencki, and for a long time its composition 

 remained undetermined. It has been called protein-chromogen 

 by some writers, but has more recently been termed trypto- 

 phane. Through the investigations of Hopkins and Cole it has 

 now been isolated and its constitution determined to be skatol- 

 amido-acetic acid. On decomposition it yields considerable 

 amounts of indol and skatol. Though the latter have long been 

 known to occur among the faecal products of digestion, they 

 have been considered to arise from putrefactive products of 

 digestion in the intestines. Hopkins and Cole have shown that 

 they are to be attributed, like the others mentioned, to the 

 action of the proteoclastic enzymes. In the course of their 

 researches they found cystin to occur side by side with tyrosin 

 and tryptophane. 



Other substances have been found to result from the 

 decomposition of proteids by hot acids and hot alkalis which 

 have been very completely investigated by various workers, and 

 which are beginning to find places in the scheme of proteid 

 zymolysis. 



Perhaps the most interesting and important of these are 

 those discovered by Fischer and Abderhalden about three years 

 ago, as they throw a light upon the relation between peptone 

 and the crystalline bodies accompanying or succeeding it in 

 intestinal digestion. On decomposing with hot acids casein, 

 edestin, egg-albumin, fibrin, the globulin of serum, and certain 

 other proteids, they found among the products a considerable 

 quantity of a-pyrrolidin-carboxylic acid, which accordingly they 

 were inclined to consider, like the ordinary amino-acids, as a 

 primary decomposition-product of the initial proteid. When, 

 however, they acted on these bodies with a strong pancreatic 

 enzyme, and continued the action for some long periods, as 

 long sometimes as several months, no trace of a-pyrrolidin- 

 carboxylic acid could be found. The solution was found, 



