62 



Scientific Proceedings (36). 



manifest that the methods are materially lacking in exactness. 

 Consequently, the results have been divergent. 



The viscosimeter * appears to offer a method which avoids these 

 difficulties, and gives constant and reliable quantitive results. The 

 viscosimeter is a capillary tube, as designed by Ostwald, on which 

 there are two markings ; the time is measured which is required by 

 a solution to flow from the upper of these markings to the lower. 

 Constant conditions of temperature are afforded by the use of a 

 constant water bath with glass walls to permit the readings. A 

 constant medium may be secured by making up a solution of the 

 medium so as to run through the viscosimeter always in a definite 

 space of time. For the purpose of testing tryptic digestion we 

 have used solutions of gelatin. The delicacy of the method may 

 be indicated by the following series of figures for variations of one 

 tenth of one per cent, in the strength of the solution : 



Normal salt solution, 



70 



y 1 ^ per cent, gelatin in above, 



71 



T % per cent. " " " 



m 



T 3 j per cent. " " " 



74f 



T 4 ff per cent. " " " 



7Si 



•j- 5 ^ per cent. " " " 



7»! 



T % per cent. " " " 



8of 



y 7 ^ per cent. " " " 



82| 



T s 5 per cent. " " " 





T 9 5 per cent. " " " 



86| 



1 per cent. " " " 



893 



It is evident that the greater the degree of digestion of the 

 gelatin, the lower will be its viscosity and the lower the corre- 

 sponding figures. 



The accuracy with which the digestive action of varying 

 amounts of the ferment upon gelatin may be determined, is indi- 

 cated by the following series of figures, in which the differences 

 are given for one hundredth of one per cent, of the trypsin, diges- 

 tion having been interrupted at the end of one hour : 



0.5 percent, trypsin: 2 minutes, 51 seconds. 

 0.49 per cent. " 2 " 53 " 

 0.48 per cent. " 2 " 56 " 



*The viscosimeter was first used in digestion experiments by Spriggs [Zeit. f. 

 physiol. Chemie, 1902, XXXV., p. 480). Owing to the fact that he used a beef extract 

 as his medium, the results were inconstant, and the method failed of any further appli- 

 cation. 



