PEPSIN DIGESTION. 447 



inorganic acids. The degree of acidity is also of the greatest importance. 

 With hydrochloric acid the degree of acidity is not the same for different 

 protein bodies. For fibrin it is 0.8-1 p. m., for myosin, casein, and vege- 

 table proteins about 1 p. m., for coagulated egg-albumin, on the con- 

 trary, about 2.5 p. m. The rapidity of the digestion increases, at least 

 to a certain point, with the quantity of pepsin present, unless the pepsin 

 added is contaminated by a large quantity of the products of digestion, 

 which may prevent its action. 



According to E. ScnuTz, 1 whose observations have been confirmed by 

 several others, the digestion products obtained in a certain time are, 

 within certain limits, proportional to the square root of the relative 

 amounts of pepsin (the ScnuTZ-BoRissow rule) while, as explained in 

 detail in Chapter II, under certain conditions another rule exists where 

 the quantity digested increases in proportion to the quantity of enzyme. 

 The kind of protein is of importance, for example, for besides what was 

 said above in regard to the fibrin, hard-boiled egg albumin is much easier 

 digested by an acidity of 1-2 p. m. HC1 than liquid egg albumin, which 

 is rather resistant to the action of gastric juice. 



The accumulation of produc'ts of digestion has a retarding action on 

 digestion, although, according to CHITTENDEN and AMERMAN 2 the removal 

 of the digestion products by means of dialysis does not essentially change 

 the relation between the proteoses and true peptones. Pepsin acts 

 more slowly at low temperatures than it does at higher ones. It is even 

 active in the neighborhood of C., but digestion takes place very slowly 

 at this temperature. With increasing temperature the rapidity of diges- 

 tion also increases until about 40 C., when the maximum is reached. 

 According to the investigations of FLAUM 3 it is probable that the rela- 

 tion between proteoses and peptones remains the same, irrespective 

 of whether the digestion takes place at a low or high temperature, so 

 long as the -digestion is continued for a long enough time. If the swelling 

 up of the protein is preve'nted, as by the addition of neutral salts, such as 

 NaCl, in sufficient amounts, or by the addition of bile to the acid liquid, 

 digestion can be prevented to a greater or less extent. Foreign bodies 

 of different kinds produce dissimilar effects, in which naturally the 

 variable quantities in which they are added are of the greatest impor- 

 tance. Salicylic acid and carbolic acid, and especially sulphates (PFLEID- 

 ERER), retard digestion, while arsenous acid promotes it (CHITTENDEN), 

 and hydrocyanic acid is relatively indifferent. By experiments with 

 salt solutions so strongly diluted that the action, on account of the strong 

 dissociation, was brought about by ions and not by the electrolytically 

 neutral molecules (min. -$ and max. ^ normal salt solutions), J. SCHUTZ 4 



1 Zeitschr. f. physiol. Chem., 9. 3 Zeitschr. f. Biologie, 28. 



2 Journ. of Physiol., 14. 4 Hofmeister's Beitrage, 5. 



