302 AN AMERICAN TEXT-BOOK OF PHYSIOLOGY. 



Products of Tryptic Digestion. — Tryptic digestion resembles peptic diges- 

 tion in that proteoses and peptones are the chief products formed, but the two 

 processes differ in a number of details. The naked-eye appearances, in the first 

 place, are different in cases in which the proteid acted upon is in a solid form ; 

 for while in the pepsin-hydrochloric digestion the proteid swells up and grad- 

 ually dissolves, under the action of trypsin it does not swell, but suffers erosion, 

 as it were, the solid mass of proteid being eaten out until finally only the indi- 

 gestible part remains, retaining the shape of the original mass, but falling into 

 fragments when shaken. In the second place, the hydrolytic cleavages seem 

 to be of a more intense nature. In peptic digestion, after the syntonin stage is 

 passed, there is a gradual change to peptone through the intermediate primary 

 and secondary proteoses. Under the influence of trypsin, according to the most 

 recent experiments, the solid proteid undergoes a transformation directly to 

 secondary proteoses (deutero-proteoses), the intermediate stages being skipped. 

 It was formerly thought that the solid proteid was converted first into a soluble 

 proteid, and that if the solution was alkaline some alkali-albumin was formed, 

 precipitable by neutralization, and comparable to the syntonin of pepsin-hydro- 

 chloric digestion. This soluble proteid was thought to be split into proteoses 

 of the hemi- and anti- groups which were then converted to the corresponding 

 peptones, according to Kiihne's schema (p. 293). There seems to be no doubt 

 that with the proteid most frequently used in artificial digestion — namely, 

 fibrin from coagulated blood— the first effect is a conversion to a soluble 

 globulin-like form of proteid ; but Neumeister finds that this does not happen 

 with other proteids, and he thinks that in the case of fibrin it is not due to a 

 true digestive action of trypsin, but to ;i partial solution of the fibrin by the 

 Inorganic salts in the liquid. In general, however, the preliminary stage of 

 a soluble proteid is missed, as also is that of the primary proteoses. The 

 proteid falls at once by hydrolytic cleavage into deutero-proteoses, and these 

 in turn are transformed to peptones. Just at this point comes in one of the 

 most characteristic differences between the action of pepsin and that of tryp- 

 sin. Pepsin cannot affect the peptones further, but trypsin may act upon 

 the supposed hemi-constituent and split it up, with the formation of a number 

 of much simpler nitrogenous bodies, most of which are amido-acids. The 

 final products of prolonged tryptic digestion are, first, a peptone which cannot 

 further be decomposed by the enzyme and which constitutes what is known 

 as anti-peptone? and, second, a number of simpler organic substances, amido- 



1 In the account of tryptic digestion as in the case of pepsin the nomenclature of Kiihne is 

 adhered to. It should he staled, however, that of late years some douht has been thrown upon 

 the existence of an anti-peptone. Siegfried [Ardkiv fur Physiologie, 1894) identifies it with a 

 body to which he <rives the name carnic acid, while Kutseher (Zeitschrift fur pkysiologische Chemie, 

 lid. 25) finds that anti-peptone prepared by Kiihne's method is at least a mixture, since it con- 

 tains the bases lysin, arginin, and bistidin. If it should he shown that what has been called 

 anti-peptone is not a peptone at all, but a mixture of simpler bodies, then it would seem that 

 the original basis of Kiihne's theory would be destroyed. There would be no occasion for 

 supposing the existence of hemi- and anti-groupings. The general schema of digestion that has 

 been developed by this theory, with its stages of proteoses and peptones, would not, however, 

 be interfered with. 



