CHEMISTRY OF DIGESTION AND NUTRITION. 231 



(trypsin, for example) are capable of splitting up a part of the peptones still 

 further. The fact that trypsin can act upon only a part of the peptone shows 

 that this latter substance is either a mixture of at least two separate although 

 closely-related peptones, to which the names of anti-peptone and hemi-peptone l 

 have been given, or it is a compound containing such hemi- and anti- groups, 

 and capable, under the action of trypsin, of splitting, with the formation of 

 hemi-peptone and anti-peptone (Neumeister). If we consider peptic digestion 

 alone, this distinction is unnecessary. The final products of peptic digestion 

 are therefore spoken of usually simply as peptones, although the name ampho- 

 peptone is also frequently used to emphasize the fact that two distinct varieties 

 of peptone are probably present. This description of the steps in peptic 

 digestion may be made more intelligible by the following schema, which is 

 modified somewhat from that given by Neumeister : 2 



Proteid. 



Syntonin. 



1 Kiihne's full theory of proteolytic digestion assumes that the original proteid molecule 

 contains two atomic groups, the hemi- and the anti- group. Proteolytic enzymes split the mole- 

 cule so as to give a hemi- and an anti- compound, each of which passes through a proteose stage 

 into its own peptone. A condensed schema of the hypothetical changes would be as follows : 



Proteid. 



Anti-albumose. Hemi-albumose. 



I I 



Anti-peptone. Hemi-peptone. 



Ampho-peptoue. 



In the detailed description of proteolysis given above, primary and secondary proteoses are pre- 

 sumably, according to this schema, mixtures in varying proportions of hemi- and anti- com- 

 pounds, or, in other words, they are ampho- proteoses. No good way of separating the anti- 

 from the hemi- compounds has been discovered except to digest them with trypsin. By this 

 means each compound is converted to its proper peptone, and by the continued action of the 

 trypsin the hemi-peptone is split into much simpler bodies (p. 241), only anti-peptone being left 

 in solution. The conception of a proteid molecule with hemi- and anti- groups and the splitting 

 into hemi- and anti-albumose is mainly an inference backward from the fact that there are two 

 distinct peptones, one of which, hemi-peptone, is acted upon by trypsin, while the other is not 

 so acted upon. The details of the splitting of the proteid under the influence of pepsin are still 

 further complicated by the fact that in some cases a part of the proteid remains undissolved, form- 

 ing a highly resistant substance to which the name antalbumid has been given. It has been shown 

 that if this substance is dissolved in sodium carbonate and then submitted to the action of trypsin, 

 only anti-peptone is formed, indicating that it contains none of the hemi- group. In fact, the prop- 

 erties of antalbumid show that it is a peculiar modification of the anti- group which may arise dur- 

 ing the cleavage of the proteid molecule, and may vary greatly in quantity in different digestions. 

 2 Lehrbuch der physiologischen Chemie, 1 893, p. 187. 



