224 GENERAL PHENOMENA OF TRYPSIN-PROTEOLYSIS. [BOOK II. 



pose, and we shall, on this account, in our brief sketch of the pro- 

 teolytic action of trypsin confine our attention, in the first instance, 

 to fibrin. 



Blood-fibrin, obtained by stirring recently shed blood with twigs 

 and then washing in a stream of water until it has become perfectly 

 white, is very readily digested by trypsin. The fibrin may be in a 

 raw or thoroughly boiled condition, some observers having employed 

 it in the one, others in the other condition. Thoroughly boiled fibrin 

 whilst it is somewhat less rapidly acted upon than the unboiled, 

 presents the great advantage that it has been freed from organic germs, 

 and especially from putrefactive bacteria, by the process, so that by 

 making use of it, it is easy to conduct a pancreatic digestion so as to 

 avoid the development of putrefaction and the subsequent complica- 

 tions which the putrefactive process introduces when its influence is 

 superadded to that of trypsin. 



As will be seen in the sequel, it is, however, easy to inhibit 

 putrefactive changes during the course of a pancreatic digestion, by 

 the use of salicylic acid or of thymol, agents which whilst they pre- 

 vent the development of putrefactive germs and therefore of putre- 

 faction, exert no unfavourable influence on the pancreatic enzymes 

 which in the presence of these chemical agents, manifest their cha- 

 racteristic activities, unchecked. 



When -boiled fibrin is placed in a 1 p.c. solution of sodium car- 

 bonate, Na 2 C0 3 , at the temperature of 40 C., it remains unchanged. 

 If a small quantity of an active glycerin extract of pancreas, or some 

 other active preparation of trypsin, be added to the fluid, solution 

 very soon commences. 



In this and other similar experiments, that most admirable preparation 

 known as Benger's ' Liquor Pancreaticus ' may be used with great advan- 

 tage. Apart from its great and uniform activity, there is no risk with it 

 (if scrupulous attention to cleanliness have been observed in boiling the 

 fibrin, and solution of Na 2 CO 3 , sterilising the flask in which the digestion 

 is carried on, &c.) that the digestion will, against the wish of the experi- 

 menter, become putrefactive. 



It is to be noted that, under the influence of trypsin, the fibrin 

 does not undergo any preliminary process of swelling, as is the case 

 when fibrin is subjected to the action of pepsin and hydrochloric 

 acid. 



As the solvent action of trypsin proceeds, the fibrin does not 

 become translucent, but its margins become more and more eroded, 

 and it diminishes in size, gradually disappearing, and often leaving 

 scarcely any residue, although as a rule a certain amount of a greyish, 

 pulverulent residue is obtained when a considerable quantity of fibrin 

 is digested by means of trypsin. 



The course of pancreatic digestion proceeds, as has been already 

 said, in a very different manner when putrefactive changes are 



