DIGESTION IN THE SMALL INTESTINE. 405 



precipitating with alcohol the proteolytic ferment may be isolated comparatively 

 pure. From the filtrate of the precipitate obtained with collodion the diastolic 

 ferment may be isolated by evaporating under an air-pump, filtering off the pre- 

 cipitate, again precipitating witli alcohol, and dissolving the precipitate in a 

 mixture of two parts of water and one of alcohol, by which proteid matter is 

 removed. The remaining substance will convert starch rapidly into sugar, but is 

 without action on proteids. 



Ktihne's method is to form an aqueous extract of a pancreas at the freezing 

 point and to precipitate with alcohol ; the precipitate is re-dissolved in water, 

 again precipitated with absolute alcohol, and the precipitate a second time re-dis- 

 solved in water and treated with acetic acid up to 1 per cent. 



The same treatment is repeated a second time, and the watery solution, after 

 the addition of acetic acid, is warmed to 40° C. and then filtered. The filtered 

 liquid is made alkaline with sodium hydrate, by which the greater part of the 

 earthy salts and tyrosin are precipitated, the trypsin or proteolytic ferment is then 

 freed by dialysis from tyrosin, peptones and other crystalline substances, and 

 finally precipitated with alcohol. 



Paschutin recommends a process for the isolation of these ferments which 

 depends upon the fact that solutions of different salts have special capabilities of 

 extracting the separate ferments. He found that sodium chloride, calcium chlo- 

 rate, and sodium sulphate were able to dissolve all three of the ferments, while 

 other solutions had special degrees of power in extracting the individual ferments. 

 Thus, the proteid ferment is especially dissolved by potassium iodide, potassium 

 arseniate, and potassium sulphate. The fatty ferment is readily extracted by 

 solutions of bicarbonate of sodium containing a small quantity of caustic soda, 

 while the diastatic ferment is most readily extracted by a solution of arseniate of 

 potassium to which a small quantity of ammonia has been added. 



2. The Action of the Pancreatic Juice on Food-Stuff*. — When study- 

 ing gastric digestion, it was seen that all the different phenomena could 

 be most conveniently studied with an artificial fluid in experiments con- 

 ducted outside of the body. The same conditions prevail in the study of 

 pancreatic digestion. An artificial pancreatic juice may be made b} r 

 three different processes : — 



First. The fresh pancreas of a dog killed some hours after a full meal is cut into 

 pieces, washed to remove the blood, and then infused for two hours in four 

 times its weight of water, warmed to 25° C, taking care to keep the mixture at 

 that temperature during the whole time of infusion. It is then to be filtered, first 

 through muslin and then through paper. Since the filtrate will be usually acid 

 from the development of fatty acids through the action of ferments on fats of the 

 pancreas, it must be neutralized with sodium carbonate. The fluid will be slightly 

 opalescent from the small amount of fat held in the form of emulsion. This 

 preparation has all the properties of pancreatic juice, although the degree of its 

 digestive action on proteids will depend upon the nutritive state of the pancreas 

 from which it was made. For, if the pancreas of a fasting animal was employed, 

 it will possess scarcely any digestive powers. 



Second. An artificial pancreatic juice may be obtained by allowing a minced 

 pancreas to remain for two clays in absolute alcohol, which is then to be filtered 

 off and the residue covered with glycerin ; this glycerin extract will contain a 

 considerable quantity of the amylolytic ferment, while the quantity of proteolytic 

 ferment, as in the first, will depend upon the condition of the gland. 



Third. The pancreas may be taken from an animal in full digestion, minced, 

 and rubbed up in a mortar with powdered glass. For each gramme of gland-sub- 

 stance, one cubic centimeter of 1 per cent, acetic acid should be added and mixed 

 thoroughly in a mortar for ten minutes, and then ten times its volume of glycerin 

 added, and the whole allowed to stand for three days. This preparation will con- 

 tain a much larger proportion of proteolytic ferment than was obtained by either 

 of the preceding processes, since the acetic acid seems to possess the power of 

 converting into ferment the zymogen, or the substance which yields the proteo- 

 lytic ferment. 



