CHAP. III.] PREPARATION OF SOLUTIONS OF TRYPSIN. 



221 



Method of 

 obtaining an 



the pancreas of 

 dead animals. 



Trypsin is very soluble in water, but it is insoluble in alcohol 

 and, strangely, in pure glycerin. The watery solution is not decom- 

 posed by long digestion at 40 C., and when evaporated it yields a 

 translucent, non-crystalline, yellowish, solid residue. Trypsin may be 

 long digested with solutions of sodium hydrate at 40 C. without 

 undergoing decomposition. 



When -boiled, trypsin yields about 20 per cent, of albumin and 

 80 per cent, of peptone (antipeptone). 



In watery solution pure(?) trypsin is able to dissolve large 

 quantities of raw fibrin with surprising rapidity, indeed well-nigh 

 instantaneously. 



1. Heidenhairi s Method. A very active glycerin 

 solution of trypsin can be obtained by the following 

 active solution method which is based upon the behaviour of the 

 of trypsin from zymogen of the proteolytic enzyme, to weak acids : 



A dog is killed from 18 to 20 hours after a full 

 meal of meat and the pancreas having been carefully 

 removed is weighed and pounded in a mortar with ground glass ; 

 the comminuted mass is allowed to remain at the temperature of the 

 laboratory for 24 hours and is then well mixed with 1 c.c. of dilute 

 acetic acid (1 per cent.) to each gramme of pancreas. To each part 

 by weight of the acid mixture there are added 10 parts by weight of 

 glycerin. In three days the glycerin solution may be filtered from 

 the insoluble residue. 



2. Roberts s Method. This has been described under the head 

 of the Diastatic Enzyme (p. 204). 



3. Kuhnds Methods of preparing active Solutions of Trypsin. 

 The complexity of the method of preparing a solution of pure (?) 



trypsin is such that Ktihne has devised methods by means of 

 which very active solutions of trypsin may be made at any time 

 from pancreatic tissue prepared according to a method of his own, 

 and which admits of being indefinitely preserved. 



Preliminary The fresh pancreas of slaughtered animals, that of 



treatment of the ox being generally used, is freed from adhering 

 pancreatic fat and connective tissue, and is then minced and 

 digested first with cold alcohol, and afterwards re- 

 peatedly extracted with boiling ether in one of the many forms of 

 fat extraction-apparatuses. The insoluble residue is then exposed to 

 the air, so as to allow the ether to evaporate, when there is left a 

 white friable solid mass. This may be kept indefinitely, and made 

 use of to prepare solutions of trypsin. It is now an article of 

 commerce in Germany, being sold by those who deal in reagents and 

 materials necessary to the physiological chemist, under the term of 

 Kuhne's ' Pankreas-pulver ' (or Pancr. siccum purissimum, nach 

 Ktihne). 



