CHEMICAL BASIS OF THE ANIMAL BODY. 877 



generally spoken of as parapeptpne. According to Finkler 1 this neutralization 

 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 Fink- 

 ler as "isopepsin." Many authors regard parapeptone, syntonin, and acid-albu- 

 min 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 proteids 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 really so converted under the influ- 

 ence 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 re- 

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

 fundamental notion of Kiihne' 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 an ti peptone, 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, etc. 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 in- 

 termediate stage corresponding to the formation of syntonin. In both normal 

 peptic and tryptic digestion antipeptone is preceded by an anti-albumose and 

 hemipeptone by a hemi-albumose. Of these the anti-albumose is closely related 

 to syntonin, and has hitherto been regarded as syntonin. The hemi-albumose 

 has not been so frequently observed ; it was, however, isolated by Meissner ; it is 

 apparently the body called by him A-peptone. It possesses several peculiar feat- 

 ures. If its solutions are heated they partially coagulate at about 60-63 C. : the 

 precipitate is soluble at about 70 C. and is reprecipitated as the temperature 

 again falls. It also yields a precipitate with nitric acid and potassic ferrocyanide, 

 and this also is soluble at the higher temperature, reprecipitating on cooling. In 

 these respects it closely resembles a proteid body observed by Bence-Jones in the 

 urine of osteomalacia. It approaches myosin in being readily soluble in a 10 per 

 cent, solution of sodic chloride. 



If, however, albumin be digested with insufficient or with imperfectly active 

 pepsin, or simply with dilute hydrochloric acid at 40 C., anti-albumose is not 

 formed, but in its place a body makes its appearance which Kiihne calls anti-albu- 

 mate. 3 Its characteristic property is that it cannot be converted by peptic digestion 

 into peptone, though it can be so changed by tryptic digestion. It is in fact the 

 parapeptone of Meissner. 



It may perhaps be advisable, now that Meissner' s parapeptone is cleared up, to 

 reserve the name parapeptone for the initial products of both peptic and tryptic 

 digestion, and to speak of anti-albumose and hemi-albumose as being both para- 

 peptones. But in this sense parapeptone will be an intermediate and not a collat- 

 eral product of digestion. 



Meissner also described a particularly insoluble form of his parapeptone as dys- 

 peptone, and another intermediate product as a metapeptone ; but further investi- 

 gation of both these bodies, as well as his B-peptone, is necessary. Under the 

 influence of dilute hydrochloric acid, anti-albumate becomes changed into a body 

 which Kiihne calls anti-albumid, and which seems identical with the very insoluble 

 proteid described by Schiitzenberger as "hemiprotein," and probably with Meiss- 

 ner 'a dyspeptone. The same body is produced at once in company with products 

 belonging to the hemi-group by the action of 3 to 5 per cent, sulphuric acid on 

 native albumin or fibrin. The following tables show the relations and genesis of 



* Pfliiger's Archiv, Bd. xiv. (1887), S. 128. 



2 Only a short account of these has as yet been published. Verhandl. d. Naturhist.-med. 

 Verein, Heidelberg, Bd. i. Heft 4, 1876. 



3 An albumate must not be confounded with an albuminate. 



