53 



184. The filtrate obtained from 183 is to be divided into 

 two portions. To the first portion apply Trommer's test. 

 A red precipitate indicates the presence of a reducing- sugar 

 — lactose. 



185. To the second portion of the filtrate apply the xan- 

 thoproteic reaction. An orange color represents the presence 

 of a proteid (1 act-albumin). 



186. To the precipitate obtained from 183 add a little 

 ether in a test-tube and agitate for a few minutes. Pour off 

 the ether upon some paper and note that it leaves a perma- 

 nent greasy stain indicating the presence of fat. 



187. To the residue left in 186 add a little dilute caustic 

 potash (0.1%). A solution is effected. Apply the xan- 

 thoproteic reaction to this fluid. An orange color denotes 

 the presence of a proteid — caseinogen. 



188. To a test-tube half filled with 0.2% hydrochloric 

 acid and 2 cc. of gastric extract add a small piece of cheese. 

 Put the tube in the incubator and examine at the next exercise 

 for peptones and intermediate products. 



189. The action of milk with pancreatic extract is some- 

 what complicated on account of the complexity of milk itself. 

 The sug-ar, fat and proteids all undergfo some change from 

 the action of the different pancreatic ferments. Perhaps the 

 most interesting of these changes is that produced in the pro- 

 teids, and is commonly called peptonization. The peptoniza- 

 tion, or digestion, of milk is quite often practised in the pre- 

 paration of food for the sick room, and is illustrated by the 

 following experiment. Dilute about 10 cc. of milk with an 

 equal volume of distilled water and add a half a gram of 

 sodium bicarbonate. Then add a few drops of pancreatic 

 extract, shake the mixture and ieep at 40° C. on the water- 

 bath for about a half an hour. Then filter and apply the 

 biuret test for peptones. The pancreatic extract from beef 

 acts more strongly upon the proteids ; that from the pig is 

 very active in converting starch into sugar. 



190. Fill a test tube half full of milk and boil it. Add a 

 tablet of rennin. Prepare another test tube in the same way, 

 but use fresh unboiled milk. Place both tubes in the water 

 bath at 38°C. After some minutes compare the tubes. The 

 boiled milk should not be coagulated. The unboiled milk. 



