BY DR. LAUDER BRUNTON. 483 



allowed to evaporate over sulphuric acid, it leaves a grayish 

 amorphous body, which contains nitrogen, and is not hygro- 

 scopic. It is sparingly soluble in water, more readily in dilute 

 acids, and digests fibrin. 



115. Digestive Action of Pepsin. Neither pepsin alone 

 nor dilute hydrochloric acid alone will digest fibrin, but when 

 mixed together they do so readily. Pepsin alone has no action 

 on fibrin whatever ; hydrochloric acid of 0.2 per cent, alone 

 causes it to swell up, but does not dissolve it for days, or even 

 weeks, at ordinary temperatures. At 35-38 C., it dissolves 

 fibrin readily in from twenty-four to forty-eight hours, but only 

 converts it into syntonin, so that the whole of the albuminous 

 matter (with the exception of a trace which Von Wittich says 

 is really converted into peptone), may be precipitated by neu- 

 tralization. Pepsin with dilute hydrochloric acid likewise 

 causes fibrin to swell and dissolves it, forming at first an opa- 

 lescent solution of syntonin which can be almost entirely pre- 

 cipitated by neutralization, a little peptone only remaining in 

 solution. Its action does not stop here, for it very quickly con- 

 verts the syntonin (parapeptone) into peptones which are not 

 precipitated by neutralization nor coagulated by boiling, but 

 are precipitated by alcohol, and possess all the characteristic 

 reactions of albuminous bodies. 



116. Products of the Digestion of Albuminous Com- 

 pounds. During digestion several substances are formed, to 

 which the names of parapeptone, dyspeptone, and metapeptone 

 have been given by Meissner. 



Parapeptone. Briicke considers that albuminous bodies are 

 converted into syntonin, and that the syntonin is transformed 

 entirely into peptones during digestion, but Meissner thinks 

 that the syntonin, instead of undergoing this transformation, 

 splits up into peptones and parapeptones. Parapeptones 

 agree with syntonin in every respect, except that they cannot 

 be converted into peptones by any amount of digestion, while 

 syntonin can be digested. When an albuminous body is sub- 

 jected to the action of gastric juice, the solution first obtained 

 yields, on neutralization, a precipitate of syntonin, which, 

 when again treated with gastric juice, is converted into pep- 

 tones. After digestion has gone on a little longer, the pre- 

 cipitate consists, according to Meissner, partly of syntonin 

 and partly of parapeptones, for he states that if this precipitate 

 is digested with fresh gastric juice, a less proportion of it than 

 of the former precipitate is converted into peptones, and that 

 this proportion diminishes more and more as digestion goes 

 on, and the remaining syntonin is split up. Briicke and others 

 have found, however, that fibrin can be completely converted 

 into peptones ; consequently, Meissner is not correct in sup- 

 posing that syntonin splits up into peptones and parapeptones. 



