METHODS FOR ESTIMATION OF PEPSIN 21 



obtained there is bound to remain the objection that this 

 means nothing more than that enzyme action may continue 

 in degrees of dilution in which the most delicate reactions 

 fail to show protein. It is utterly impossible for any man 

 at the present time to say whether the ferments are of a 

 proteid nature or not. When a French physiologist gave it 

 as his opinion that ferments are in no sense material, but 

 energy alone, his statement called forth vehement opposi- 

 tion. To-day, however, when a slow but sure change is 

 taking place in our fundamental ideas about atoms, and the 

 very basis of our older .conception of nature, the duality of 

 matter and force, is decidedly wavering, such heretical 

 theories would scarcely excite anything like the same 

 indignation. 



Methods for Estimation of Pepsin. Numerous methods 

 have been applied to the quantitative determination of 

 pepsin. Griitzner estimates the amount of coloring mat- 

 ter passing into solution in the digestion of fibrin stained 

 with carmine, using a wedge-colorimeter. 58 In Mett's 

 method the length of a column of coagulated albumin 

 enclosed in a fine glass tube is measured after a fixed period 

 of digestion, Hammerschlag estimates by precipitation 

 with Esbach's reagent the amount of undigested protein 

 remaining after digestion of a known albumin solution for a 

 certain fixed time. Spriggs tries to draw a conclusion from 

 the loss of viscosity of a protein solution as to the progress 

 of its digestion. Vollhard begins with a known solution of 

 casein ; throws out the undigested casein by sodium sulphate, 

 and estimates the amount of digested protein in the filtrate 

 by its alkali-binding power determinable by titration : the 

 more advanced the digestion the more potassium or sodium 

 hydrate required. E. Fuld arranges a series of small 

 beakers each containing the same quantity of a hydrochloric 

 acid solution of a pure protein, edestin, adding graduated 

 quantities of the solution whose peptic quantity is to be 



88 P. v. Griitzner (Tubingen), Pfliiger's Arch., 144, 545, 1912. 



