718 P ROTE IDS. [A PP. 



it offers towards trypsin ; the name hemipeptone, given to the former, 

 signifies that this peptone is the twin or correlative half of antipeptone. 



We have seen (p. 243) that when any proteid is digested with 

 pepsin, what we may preliminarily call a bye-product makes its appear- 

 ance. This bye product, which has many resemblances to acid- 

 albumin or syntonin, appearing as a neutralisation precipitate soluble 

 in dilute acids and alkalis but insoluble in distilled water, is generally 

 spoken of as parapeptone. According to Finkler 1 this neutralisation 

 precipitate is especially abundant if the pepsin be previously modified 

 by exposure to a temperature of 40 to 60 C. The pepsin thus modified 

 is spoken of by Finkler as 'isopepsin.' Many authors regard parapep- 

 tone, syntonin, and acid-albumin as being the same thing. Meissner 

 however gave the name parapeptone to a body, which need not and 

 probably does not make its appearance during normal natural digestion 

 or during artificial digestion with a thoroughly active pepsin, but which 

 is formed when proteid s are subjected to the action of weak hydrochloric 

 acid, either alone or in company with an imperfectly-acting pepsin, and 

 which in certain characters is quite distinct from ordinary syntonin or 

 acid-albumin. Its distinguishing feature is that it cannot be changed 

 into peptone by the action of even the most energetic pepsin, though it 

 is readily so converted under the influence of trypsin ; otherwise it very 

 closely resembles syntonin. We have here an indication that the simple 

 characters by which we have described acid-albumin may be borne 

 by bodies having marked differences from each other. The researches 

 of Kiihne 2 have thrown an important light on these differences. The 

 fundamental notion of Kuhne's view is that an ordinary native albumin 

 or fibrin contains within itself two residues, which he calls respectively 

 an anti-residue and a hemi-residue. The result of either peptic or 

 tryptic digestion is to split up the albumin or fibrin, and to produce on 

 the part of the anti-residue antipeptone, and on the part of the hemi- 

 residue hemipeptone, the latter being distinguished from the former by 

 its being susceptible of further change by tryptic digestion into leucin, 

 tyrosin, &c. Antipeptone remains as antipeptone even when placed 

 under the action of the most powerful trypsin, provided putrefactive 

 changes do not intervene. 



Before the stage of peptone (whether anti- or hemi-) is reached, 

 there is an intermediate stage corresponding to the formation of synto- 

 nin. In both normal peptic and tryptic digestion antipeptone is 

 preceded by an anti-album ose, and hemipeptone by a hemi-albumose. 

 Of these the anti-albumose is closely related to syntonin, and has 



3 Pfliiger's Archiv, xiv. (1877), S. 128. 



2 Only a short account of these has as yet been published. Verhand. d. 

 hist-Med. Ver-Heidelbg. Ed. i. Hf. 4, 1876. 



