450 PRACTICAL PHYSIOLOGY 



The various reactions described on page 224 should be applied to 

 each of the separated products. 



Method of Estimating Activity of Pepsin Solutions. (1) Grutzner's 

 Method. Fibrin, purified as above described, is stained with carmine 

 solution, 1 and washed free of adherent stain. Equal weighed quantities 

 are then placed in two test-tubes, and 10 c.c. of 0*2 per cent, hydro- 

 chloric acid are added to each. Equal quantities of the pepsin 

 solutions which it is desired to test are added, and the tubes placed 

 in the incubator. As the fibrin becomes digested the carmine is 

 liberated, and stains the solution. The more deeply stained solution, 

 therefore, contains the stronger ferment. The exact amount of carmine 

 liberated may be determined by comparing the digests with an artificial 

 scale consisting of ten solutions of carmine of different known strengths. 



(2) Mett's Method. A narrow glass tube, 1 to 2 mm. in diameter, is 

 filled with egg white, and is then heated so that a column of coagulated 

 albumin is obtained. It is then cut into segments of equal length and 

 two of these are placed in a test-tube which contains the pepsin 

 solution acidified with 0*2 per cent, hydrochloric acid. Two similar 

 tubes are placed in another test-tube with the other pepsin solution. 

 Both are placed in the incubator for several (10) hours. The length 

 of dissolved proteid column is then measured in both cases, and the 

 desired result is obtained by squaring this distance. 



Thus if in one test-tube the length were 2, and in the other 3, the 

 strength of the two pepsin solutions has the ratio of 4 to 9. 2 



CHAPTER VIII. 

 PANCREATIC DIGESTION. 



The Products of Digestion of Proteids by Trypsin. The method of 

 preparing the digest, and the chemical nature of the products of it, 

 have already been described on page 227. All that remains to describe 

 here is the method for separating the more important of these products 

 (Tyrosin, Leucin, and Antipepton). If it be desired to isolate the 

 hexone bases, the method described on page 426 may be employed. 



1 Dissolve 1 gr. carmine in 1 c.c. ammonia and mix with 400 c.c. distilled water. 

 Place in a loosely stoppered bottle till the smell of ammonia has become faint, and 

 then cork tightly. 



2 This law is only approximately correct. 



