X.] PANCREATIC DIGESTION. 8 1 



4. II. Proteolytic Action and its Conditions (Trypsin the fer- 

 ment). 



(a.) Half-fill three test-tubes A, B, C, with i per cent, solution 

 of sodium carbonate, and add 5 drops of glycerin pancreatic extract 

 or liquor pancreaticus in each. Boil B, and make C acid with dilute 

 hydrochloric acid. Place in each tube an equal amount of well- 

 washed fibrin, plug the tubes with cotton-wool, and place all in a 

 water-bath at 40 C. 



(k.) Examine them from time to time. At the end of one, two, 

 or three hours there is no change in B and C, while in A the fibrin 

 is gradually being eroded, and finally disappears, but it does not 

 swell up, the solution at the same time becoming slightly turbid. 

 After three hours, still no change is observable in B and C. 



(c.) Filter A, and carefully neutralise the filtrate with very 

 dilute hydrochloric or acetic aqid = a precipitate of alkali-albumin. 

 Filter off the precipitate, and on testing the filtrate, peptones are 

 found. The intermediate bodies, the albumoses, are not nearly so 

 readily obtained from pancreatic as from gastric digests. 



(d.) Filter B and C, and carefully neutralise the filtrates. They 

 give no precipitate. No peptones are found. 



(e. ) Test the proteolytic power of an extract of Kiihne's " pancreas powder " 

 (Lesson X., I, e). For this purpose the salicylic and alkaline extracts are 

 mixed with well-washed fibrin and digested at 40 C. for ten hours or longer. 

 The vessel is covered with thymolised paper. Strain through linen and 

 then filter. Test the digest for peptones. It is difficult to get any albumoses 

 after this time ; the anti-albumoses are already converted into anti-peptones, 

 the hemi-albumose into hemi-peptone, and some of the latter is decomposed 

 into leucin and tyrosin. 



As putrefaction takes place with great rapidity in pancreatic 

 digests, it is essential to prevent this either by the addition of an 

 alcoholic solution of thymol or chloroform water (5 cc. chloroform 

 to i litre water). To get satisfactory results it is better to do it on 

 a somewhat larger scale (Salkowski}. 



Tryptic Digestion. 



50 grams fibrin + 200 cc. alkaline (carbonate of soda i per cent.) chloroform 

 water + liq. pancreaticus digested for 36 hours ; then boil and filter. 



Residue ; coagulated Filtrate (A) (reaction with bromine) 



Proteid. concentrated by evaporation 



and allowed to stand. 



I 



Deposition (B) of Filtrate (C) further 



Tyrosin. concentrated ; Leucin 



and Peptone. 



