182 LABORATORY WORK ON GASTRIC DIGESTION. [BOOK II. 



of the liquids is determined with the aid of a decinormal solution of 

 baryta or soda ; the former is preferred by Berthelot and Richet, but 

 for reasons which do not appear sufficient. 



The ' coefficient de partage ' is found by dividing the volume of 

 standard alkaline solution required to neutralize a given volume, say 

 10 c.c. of the aqueous, by the volume required to neutralize an equal 

 volume of the ethereal solution. 



Before determining the acidity of the ether, the liquid is diluted 

 with say 10 c.c. of absolute alcohol ; there is thus obtained an 

 alcoholic-ethereal liquid which is miscible with water. 



After the first determination, the process of shaking the gastric- 

 juice and ether may be repeated a second or even a third time, and 

 also the titrations. 



In cases where the exact ' coefficient de partage ' of the acids 

 soluble in ether is desired, the ethereal liquid obtained by agitation 

 should be shaken with water and the coefficient be again deter- 

 mined. 



8. Determination of the Peptic activity of different samples of 

 Pepsin or of Solutions containing Pepsin. 



As we cannot separate pure pepsin so as to ascertain its amount, 

 we are obliged to judge of the relative richness in pepsin of different 

 preparations by determining their relative activity. We may do so 

 either by observing the relative amounts of a proteid which can be 

 dissolved in a given time, or by determining the relative times occu- 

 pied in the solution of a given amount of proteid. 



Method of In this as in all other cases, a digestive liquid must 

 Bidder and be first made by mixing a known weight or volume of 

 Schmidt and eac h o f the preparations under examination with water 



containing either one or two parts of HC1 per 1000. 

 The same volume of each digestive liquid is taken and placed in 

 an incubator, and to each there is then added the same weight of hard- 

 boiled white of egg cut in pieces of approximately the same size and 

 shape. A portion of the same sample of boiled white of egg is ana- 

 lysed so as to determine the proportion of solid matter which it 

 contains. After, say 24 hours, the liquids are filtered and the undi- 

 gested white of egg in each case is dried and weighed. In this way 

 is found the amount of albumin which has been dissolved in each 

 case, and this will represent the relative peptic activities of the pre- 

 paration employed. 



Brttcke's A known weight or volume of the preparations 



method. to be compared is mixed with water and hydrochloric 



acid, so as to yield solutions which contain exactly 1 part of HC1 in 

 1000. At the same time an aqueous solution of HC1 of the same 

 strength is prepared. Seven mixtures of each of the digestive liquids 

 with various proportions of the acidulated water are then made and 



