PANCREATIC DIGESTION. 61 



and keep it at 40 C. Within a few minutes a solid coagulum 

 forms, and thereafter the whey begins to separate. 



(b.) Repeat (a.), but add a grain or less of bicarbonate of 

 soda to the milk. Coagulation occurs just as before, so that 

 this ferment is active in an alkaline medium. 



(c.) Boil the ferment first. Its power is instantly 

 destroyed. 



9. Action on Milk. 



(a.) Dilute cow's milk with 5 volumes of water. Test 

 a portion, and note that acetic acid throws down a flocculent 

 precipitate of casein. Place some of the diluted milk in a 

 test-tube, add a drop or two of pancreatic extract, or the 

 Liquor Pancreaticus of Benger. Expose on a water-bath at 

 40 C. for half an hour. Note that the casein is first curdled 

 and then dissolved, and as this occurs, the milk changes 

 from a white to a yellowish colour. 



(b.) Divide the fluid of (a.) into two portions, A and B. To 

 A add dilute acetic acid, there is no precipitation of casein, 

 which has been converted into peptones. To B add caustic 

 soda and dilute copper sulphate, which give a rose colour, 

 proving the presence of peptones. 



10. To Peptonise Milk. A pint of milk is diluted with a 

 quarter of a pint of water, and heated to a luke-warin tempera- 

 ture, about 140 F. (or the diluted milk may be divided into two 

 equal portions, one of which may be heated to the boiling point 

 and then added to the cold portion, the mixture will then be of 

 the required temperature). Two tea-spoonfuls of Liquor Pan- 

 creaticus, together with about fifteen grains or half a level tea- 

 spoonful of bicarbonate of soda are then mixed therewith. The 

 mixture is next poured into a jug, covered, and placed in a warm 

 situation to keep up the heat. In a few minutes a considerable 

 change will have taken place in the milk, but in most cases it is 

 best to allow the digestive process to go on for ten or twenty 

 minutes. The gradually-increasing bitterness of the digested 

 milk is unobjectionable to many palates; a few trials will, how- 

 ever, indicate the limit most acceptable to the individual patient ; 

 as soon as this point is reached, the milk should be either used or 

 boiled to prevent further change. From ten minutes to half 

 an hour is the time generally found sufficient. It can then be 

 used like ordinary milk. 



