HANDBOOK FOR BIO-CHEMICAL LABORATORY. 35 



Trypsin. 



Preparation. 1. The fresh pancreas ol an ox is freed from 

 adhering fat and connective tissue and then minced and di- 

 gested first with cold alcohol, and afterwards extracted with 

 boiling ether in an extraction apparatus. The insoluble resi- 

 due is then exposed to the air, so as to allow the ether to 

 evaporate, when there is left a white, friable mass. This 

 may be kept indefinitely, and made use of to prepare solu- 

 tions of trvpsin. (Called Killings pancreas powder.) 



One part by weight of the above pancreas powder is digested 

 at 40 C. for 4 hours with 5 parts of 0.1$ salicylic acid solu- 

 tion. The residue after being squeezed is further digested for 

 12 hours with 5 parts of 0.25$ Na a C0 3 solution, and the resi- 

 due is again squeezed out. The acid and alkaline extracts 

 are mixed together, the whole made up to contain 0.25-0.5$ 

 Ka 2 C0 3 , and digested for at least a week in the presence of 

 0.5$ thymol. By this means all the first-formed albumoses are 

 fully converted into peptones ; this is essential. At the end 

 of the week the fluid is allowed to stand in the cold for 24 

 hours, filtered, faintly acidulated with acetic acid, and satu- 

 rated with neutral ammonium sulphate. By this means all the 

 trypsin is separated out and maybe collected on a filter, where 

 it is washed with (XH 4 ) 2 S0 4 (saturated solution) till free 

 from peptones. It is now finally dissolved off the filter in a 

 little 0.25$ NA a C0 3 solution, to which thymol is added, and 

 thus an extremely active and pure digestive solution is ob- 

 tained. The ammonium sulphate present may be gotten rid 

 of by dialysis. (Kuhne.) 



2. The pancreas is carefully removed from a dog killed 18 

 to 20 hours after a full meal and weighed. It is then pounded 

 up in a mortar with pure quartz sand or glass powder and 

 allowed to stand at the temperature of the laboratory for 24 

 hours and then mixed with 1 c.c. of 1$ acetic acid for every 

 gramme of pancreas, then for each part of the gland mass add 



