CHAP. II.] LABORATORY WORK ON GASTRIC DIGESTION. 183 



placed in seven separate vessels, the proportion of digestive liquid to 

 water being arranged as follows t-r- 



(1)16:0, (2)8:8, (3)4:12, (4)2:14, (5)1:15, 

 (6)0-5:15-5, (7) 0'25 :157. 



Thus if we had n samples of pepsin to examine, we should have 

 n sets of seven vessels, each set containing the dilutions according to 

 the above plan. 



Now, into each of the vessels is placed a flocculus of well-washed 

 blood-fibrin, and all are placed in an incubator at about 40 C. 



The vessels are then closely observed in order to find those of 

 the different sets in which digestion has proceeded to the same ex- 

 tent. If we had, for instance, two sets A and B, and we found 

 that in vessel 1 of set A digestion occurred in the same time as in 

 vessel 2 of set B, we should conclude that the digestive activity, which 

 is, within wide limits, proportional to the quantity of pepsin, of B 

 was twice as great as that of A. 



For all the precautions to be followed in employing this method 

 the reader is referred to the description given by its author 1 ; it has 

 now been generally superseded by the methods to be described below. 

 Grttnfcagen's Well washed blood-fibrin is placed for several hours 

 method 2 . i n water containing two parts of HC1 per litre. When 



the fibrin has swollen, it is placed upon filters to drain. If several 

 solutions of pepsin have to be examined, a given weight of the swollen 

 fibrin is placed upon as many filters as there are solutions, and then a 

 measured volume, say 1 c.c., of each of the liquids is poured over the 

 contents of a corresponding funnel. After some minutes, the contents 

 of the funnel begin to dissolve, as is evidenced by liquid beginning to 

 drop from the funnel. The relative peptic activity may be judged of 

 by counting the drops which fall in a given time, or by the volume of 

 liquid which is collected in a given time, or by the time occupied in 

 the complete liquefaction of the whole mass. 



Thus, to take an example. In one of v. Wittich's experiments 3 , 

 in which he was compariDg the relative richness in pepsin of a gly- 

 cerin extract of the mucous membrane of the fundus and of the 

 pylorus, designating the first 1 and the second 2 : he added 1 c.c. of 

 the extract in each case to swollen fibrin placed in two funnels, 

 which were maintained at the temperature of the room. In 1 (fundus) 

 dropping began in two minutes, and at the end of two hours 13 c.c. of 

 fluid had been collected. In 2 (pylorus) dropping began in ten minutes, 

 and at the end of two hours 4'5 c.c. of fluid had been collected. 



Griitzner's Although no very accurate way of testing the rela- 

 tive amounts of pepsin contained in two extracts exists, 

 the one which is most generally useful is Griitzner's Colori metric 



1 Briicke, 'Vorlesungen,' "Quantitative Bestimmung des Pepsins," p. 302 et seq. 



2 Griinhagen, "Neue Methode die Wirkung des Magen-Pepsin zu veranschaulichen 

 nnd zu messen." Pfliiger's Archiv, Vol. v. (1872), p. 203. 



3 v. Wittich, "Das Pepsin und seine Wirkung auf Blutfibrin." Pfliiger's Archiv, 

 Vol. v. p. 435. 



