CLEA VA GE THEOR Y OF PROTEID DIGESTION. 409 



Five hundred grms. of unboiled fibrin, squeezed as dry as possible with the 

 hand, were placed at room temperature for twenty-four hours in 5 litres of 0'2 

 per cent, hydrochloric acid ; the mixture was then heated to 37 C., and 

 100 c.c. of gastric extract added. Solution took place inside an hour, after 

 which the fluid was filtered through a hair sieve, digestion stopped by neutral- 

 isation, and the neutralisation precipitate filtered off. This precipitate is stated 

 to be essentially antialbumose. It was long washed with water, and did not 

 then dissolve easily in 0'2 per cent, hydrochloric acid, so was heated for some 

 hours at 40 C. This acid solution was treated with an equal volume of strong 

 gastric extract in 0*2 per cent, hydrochloric acid for forty-eight hours, again a 

 heavy neutralisation precipitate was obtained. This precipitate, after washing 

 with water thoroughly till no biuret peptone reaction was given, was treated 

 with sodium carbonate solution of 2*5 per cent., in ichich it ivas not easily soluble, 

 and the solution was not clear until it had been digested for forty-eight hours at 

 48 C. with trypsin. Even then, on neutralising, a precipitate behaving like 

 antialbumid was obtained. Kedissolved in 2 '5 per cent, sodium carbonate solu- 

 tion, and redigested with trypsin, it was again precipitated in clotlike flakes, 

 and was only very slowly and partially converted by repeated tryptic digestion. 



Here, again, there is no guarantee, after heating the first neutralisation 

 precipitate for some hours with 0'2 per cent, hydrochloric acid in order 

 to dissolve it, that a natural digestion product remains to be dealt with 

 in the subsequent processes. In addition, the obstinate resistance of the 

 substance to both peptic and tryptic digestion proclaims it a product of 

 experimental procedure, and not a true stage in natural or uninterrupted 

 digestion. 



Hemialbumose. Kiihne and Chittenden 1 also obtained a precipitate, to 

 which they gave the name of hemialbumose ; this was obtained from the pro- 

 ducts of fractional peptic digestion in the filtrate after the removal of the 

 so-called antialbumose by neutralisation. This filtrate was concentrated to one- 

 fourth of its volume, acidified with acetic acid, boiled and filtered from a scanty 

 coagulum, again concentrated and precipitated by the addition of excess of 

 alcohol. In this precipitate by alcohol, the authors recognised, besides peptones, 

 two forms of albumose, soluble and insoluble hemialbumose. The precipitate 

 was rubbed up with cold water, until the wash water no longer gave the biuret 

 reaction. A part of the albumose (soluble hemialbumose) went into solution, 

 accompanied by all the peptone, a part remained insoluble (insoluble hemi- 

 albumose). The latter substance was not pure, but contained a proteid substance 

 insoluble in 2 per cent, acetic acid and in sulphuric acid of 0'4 per cent., and 

 with difficulty soluble in dilute caustic soda solution. The " insoluble hemialbu- 

 mose " was separated from this by treating with boiling water. From solution 

 in boiling water a part of the "insoluble hemialbumose" was precipitated as 

 the solution cooled. This was separated ; the remainder was precipitated from 

 the cold solution and added to it. The " soluble hemialbumose " was obtained, 

 free from its admixture with peptone in the cold water extract, by Salkowski's 

 method of boiling with excess of sodium chloride and dilute acetic acid so as 

 to form a saturated solution, washing the precipitate with saturated sodium 

 chloride solution, dissolving in water and dialysing until the dialysate gave 

 no reaction for chlorides with silver nitrate. 



These hemialbumoses on tryptic digestion yielded leucine and tyrosine 

 abundantly, but could not be completely broken up by such digestion, 

 a variable amount of peptone being always left, no matter how prolonged 

 the digestion, which could only (on the cleavage theory) be antipeptone, 

 and so pointed to impurities in the form of anti-compounds in these 



1 Loc. cit. 



