CLE. 1 1 : !<;/: THEOR Y OF PROTEID DIGESTION. 405 
with acid alone, but incomparably more slowly. The acid and ferment 
seem to mutually assist each other. Pepsin alum- is inactive, the acid 
alone acts with extreme slowness, but in the presence of the acid the 
ferment speedily dissolves the proteid, which is then rapidly attacked by 
the acid and converted into acid albumin. 
When the proteid undergoing digestion is fresh fibrin which has not been 
previously subjected to heat coagulation, a body possessing the properties of 
a globulin is found in the solution in the first stage of digestion, before or 
just when complete solution has taken place; a similar body is also said to be 
formed in small quantity as a first product of digestion of other forms of 
proteid. 1 In a recent paper it is stated by Arthus and Huber 2 that this 
globulin is simply dissolved fibrin. These authors found such a body co- 
agulating at 56 J C. on digesting unboiled fibrin; but boiled fibrin yielded no 
such product. They also determined that " Witte's Peptone " dissolved un- 
boiled fibrin, at 40 ' C. giving a solution which coagulated on heating at 
56°, 68 D , and 75° C. 
The acid albumin is next attacked by the pepsin and further 
altered, giving rise to a number of substances called albumoses, proteoses, 
or propeptones, ami these in turn are slowly and incompletely con- 
verted into peptones. Here the action of pepsin ceases. 
Cleavage theory of proteid digestion.— The cleavage theory of 
proteid digestion was first enunciated by Kiihne in 1877. 3 He describes 
the digestion of albumins by trypsin as taking place in two stages : in 
the first stage the albumin is changed into peptone (amphopeptone) ; 
in the second stage, one-half of this peptone (hemipeptone) is further 
changed, while the other half (antipeptone) remains unaltered. Peptic 
digestion is not essentially different from the first stage of tryptic, and 
while it is not possible to obtain two bodies from pepsin peptone, still it 
is probable that this substance is a mixture of two bodies, antipeptone 
and hemipeptone, as is also the case after the first stage of tryptic 
digestion. 
Unable to isolate two bodies from the end products of peptic 
digestion, one of which should remain unchanged when subjected to 
tryptic digestion, while the other broke up under like treatment into 
leucine and tyrosine, Kiihne surmised that the cleavage might take 
place earlier in the process of peptic digestion, and that more success 
might attend an attempt to separate the precursors of anti- and hemi- 
peptone, namely, the corresponding albumoses, by interrupting peptic, 
digestion at an early stage, and experimenting upon the products then 
in solution. By interrupting peptic digestion at an early stage, two 
substances were obtained : one was a neutralisation precipitate, which, on 
tryptic digestion, afterwards yielded only antipeptone, and was hence 
named antialbumose ; the other, obtained from the filtrate, was de- 
composed by trypsin, with formation of leucine and tryosine, and was 
hence named hemialbumose.* Kiihne 5 also reinvestigated the action of 
acids, renaming Schiitzenberger's hemiprotem antialbumid, and a body 
1 Briicke, Sitzungsb. d. k. Akad. d. fPissensch., Wien, 18.59, Bd. xxxvii. S. 1S2 ; Otto, 
Ztschr. f. physiol. Chem., Strassburg, 1883, Bd. viii. S. 129: Hasebroek, ibid., 1887, Bd. 
xi. S. 318; A. Herrmann, ibid., 1S87, Bd. xi. S. 508; Neumeister, Ztschr. f. Biol.. 
Miinchen, 1890, Bd. xxvii. S. 310. 
2 Arch, dephysiol. norm. <t path., Paris, 1893, tome xxv. p. 447. 
3 Verhandl. d. naturh.-m.ed. Ver. zu Heidelberg, 1877, X. F., Bd. i. S. 236. 
4 Vide infra. 5 Loc. cit. 
