22 GASTRIC DIGESTION OF PROTEINS 



determined; after appropriate time for digestion sodium 

 chloride is added to all of the samples, and the result esti- 

 mated by the degree of turbidity ensuing (absent in fully 

 digested specimens). M. Jacoby and Solms substitute ricin 

 for edestin; Gross casein; and Rose protein (globulin) of 

 garden-pea in modification of the latter method. 59 



Law of Pepsin Fermentation. Based upon these 

 methods it has been thought possible to establish a "fer- 

 mentation law" for the activity of pepsin. The Schiitz- 

 Borissow rule, making the effectiveness of the pepsin 

 proportionate to the fourth root of its quantity, has at- 

 tained considerable popularity and has been very much 

 discussed. 60 Without going into the details of ferment 

 activity it may be stated that P. v. Grutzner 61 has concluded 

 from his careful and critical studies in reference to pepsin 

 and trypsin * t that there is no uniform law prevailing during 

 the entire course of a process. . . . In the processes of 

 digestive fermentation at the beginning one rule prevails, 

 which is not the same for the intermediate stage or for the 

 terminal part. Moreover, as stated, the absolute and rela- 

 tive quantity of a ferment will cause variation of the law and 

 it is impossible to speak of a law in the usual meaning of 

 the term for any one ferment." 



Propepsin. Pepsin does not exist in completed state in 

 the glands of the gastric mucosa, as shown by the studies of 

 Ebstein and Griitzner and those of Langley, but in the form 

 of a pro ferment which (in contrast to pepsin, which is very 

 sensitive to alkalies) is resistant to alkali, and immediately 

 changes into pepsin when brought in contact with hydro- 



68 Cf . critique of methods, P. v. Grutzner ( Festschr. f . G. Fano ) , Arch, di 

 Fisiol., 7, 223, 1909; E. Henrotin, Ann. de la Soc. roy. des Sciences md. et 

 natur. de Bruxelles, 18, fasc., 2, 1908; W. C. Rose, Arch, of Intern. Med., 5, 

 459, 1910; A. Fubini, Gaz. Osped., SO, 409, 1909; P. W. Cobb (Cleveland), 

 Amer. Journ. of Physiol., 13, 448, 1905. 



w Cf. J. Schutz (Laborat. Hof meister ) , Zeitschr. f. physiol. Chem., SO, 1, 

 1900; Reichel, Wiener klin. Wochenschr., 1908, No. 30. 



64 P. v. Grutzner, Pfluger's Arch., 141, 115, 1911. 



