40 THE ALBUMINS. 



can be no doubt that a phenyl-a-amino-propionic acid radicle is pres- 

 ent in all albumins. 



2. The same is true of a tyrosin radicle (oxyphenyl-alanin- 

 p-oxyphenyl-a-amino-propionic acid). 



III. Heterocyclic radicles. 



1. Radicles of the pyrrol group. Through the researches of E. 

 Fischer and his pupils it has been shown that a prolin radicle (a-pyr- 

 rolidin carbonic acid) is represented in all albumins; oxyprolin 

 (oxy-a-pyrrolidin carbonic acid) is usually obtained at the same time. 



2. Radicles of the indol group. The indol group is probably 

 represented in the albuminous molecule by the tryptophan complex, 

 which Hopkins and Cole have identified as skatol-amino-acetic acid. 

 This radicle is the mother-substance of indol, skatol, skatol-carbonic 

 and skatol-acetic acids, all of which are formed during albuminous 

 putrefaction and in part also on fusion with caustic alkali. The 

 kynuric acid of dogs' urine likewise (a-oxy-/3-quinolin carbonic acid) 

 is a derivative of tryptophan, as also possibly skatosin, which has been 

 encountered among the products resulting from pancreatic autolysis, 

 as also on prolonged peptic digestion of serum-albumin. 



The presence of the various radicles just considered has been 

 largely established by a study of the decomposition-products of the 

 albumins which result on hydrolysis, by means of boiling mineral 

 acids and alkalies, proteolytic ferments, etc. Other methods in part 

 at least yield other end-products, which, however, so far as they 

 have been studied, can readily be reduced to the same radicles that 

 are furnished by hydrolysis. 



As a result of putrefactive changes indol, skatol, skatol-carbonic 

 acid, and skatol-acetic acid are obtained, all of which are derivatives of 

 the tryptophan complex ; further, phenyl-propionic (hydrocinnamic) 

 acid, phenyl-acetic acid, and phenyl-ethylamin, all three derivatives 

 of phenyl-amino-propionic acid ; further, para-oxyphenyl-propionic 

 (hydroparacumaric) acid, para-oxyphenyl-acetic acid, cresol, and 

 phenol, all derivatives of para-oxy phenyl-amino-propionic acid 

 (tyrosin) ; then a-amido-valerianic acid and putrescin, derivatives of 

 arginin ; cadaverin from lysin ; hydrogen sulphide from cystin, etc. 



On oxidation with potassium bichromate and sulphuric acid ben- 

 zoic acid has been obtained ; with barium permanganate guanidin is 

 formed. 



On fusion with caustic alkali leucin, tyrosin, indol, skatol, hydro- 

 gen sulphide, and methyl mercaptan are quite constantly obtained, 

 the most notable being indol and skatol, whose formation under 

 these conditions is generally regarded as one of the most character- 

 istic reactions of the albumins. 



With any method, of course, products are also obtained which 

 are not primary components of the albuminous molecule, but which 

 result on further destruction of the essential radicles. Such bodies 

 are carbon dioxide, oxalic acid, formic acid, acetic acid, butyric 

 acid, isovaleric aldehyde, acetone, ammonia, hydrogen sulphide, etc., 



