Reactions of certain Sunthesised Proteid-like Substances. 339 



if a trace of a soluble salt of either barium, strontium, calcium, 

 magnesium, or sodium be added, a pronounced coagulum is obtained 

 011 heating. This point will be returned to you in a subsequent- 

 section, but the similarity to dialysed serum-albumen may be pointed 

 out, as that substance is stated not to coagulate when heated.* 



The solution does not coagulate spontaneously on standing, 

 neither will the addition of "fibrin ferment (i.e., a nucleoproteidf) 

 induce coagulation. It gives a typical xanthoproteic reaction, a 

 violet with copper sulphate and potash, a dark heliotrope-purple 

 with cobalt sulphate and potash, and a faint yellow with nickel 

 sulphate and potash. It also gives Frdhde's sulpho-molybdic reaction ; 

 I may, however, remark that I found that several substances chemi- 

 cally allied to proteids yield this reaction, which is therefore not 

 diagnostic of proteids alone. An alcoholic solution of alloxan gives 

 with the solid plates a brilliant red coloration (Krasser'sJ reaction) 

 similar to that produced with plates of serum-albumen. Negative 

 results were obtained with the reactions associated with the names of 

 Liebermann, Adamkiewicz,|| and Millon.^f 



The solution is neutral and laevorotatory (a D = 52), and if treated 

 with pepsin and a O2 per cent, hydrochloric acid, or by an alkaline 

 solution of trypsin, for several days at 38 C. it does not peptonise. 



Qualitative analysis shows that this substance does not contain 

 phosphorus in its molecule. 



It is precipitated from solution by mercuric chloride, silver nitrate, 

 and lead acetate. These precipitates yield the same colour reactions 

 as the original substance. 



The precipitate formed by the addition of lead acetate, like that 

 obtained by the addition of this substance to a proteid solution, 

 redissolves on the passage of a current of sulphuretted hydrogen 

 through the solution in which it is suspended, and judging by 

 chemical tests alone, the nature of the substance is unchanged by the 

 processes of precipitation and redissolving. Its physiological action 

 is, however, markedly changed, as will be shown later on. 



The original solution is readily precipitated by trichloracetic, 

 phosphotungstic, phosphomolybdic acids, and by acetic acid and 

 potassium ferrocyanide, as well as by salicylsulphonic acid ; the pre- 

 cipitate formed by this last substance is coagulated by heating in a 

 manner similar to the coagulation produced by heating the pre- 

 cipitate resulting from the addition of this substance to a proteid 



* Schmidt and Aronstein, ' Pfluger's Arcliiv,' vol. 8, p. 75, 1874. 



f Vide Halliburton, ' Journ. Physiol.,' vol. 18, p. 306, 1895. 



J Krasser, ' Monat. i'iir Chem.,' vol. 7, p. 673 ; ' Muly's Jahresb.,' vol. 16, p. 1. 



Liebermann, ' Maly's Jahres.,' vol. 18, p. 8. 



|| Adamkiewicz, 'Ber. d. deut. Chem. Gresell.,' vol. 8, p. 761. 



If Millon, ' Comptes Kendus,' vol. 28, p. 40. 



