56 CHEMICAL PHYSIOLOGY. 



of distilled water, and 1 drop of liquor ferri perchloridi. 

 The blue solution thus obtained is changed to yellow by 

 lactic acid, while it is not affected by 0*2 per cent. HC1 

 (Uffelmann's Reaction). 



These reactions for a mineral acid are specially to be noted, as 

 they are sometimes used clinically for ascertaining the presence 

 or absence of hydrochloric acid e.g., in a vomit. This acid is 

 almost invariably absent from the gastric juice in cancer of the 

 stomach. It is to be noted, however, that the presence of pep- 

 tones interferes with the delicacy of these reactions. 



LESSON VIII. 

 PANCREATIC DIGESTION. 



1. Preparation of Artificial Pancreatic Juice. 



(a.) Use part of the pancreas of an ox twenty-four hours 

 after the animal was killed. Mince a portion of the pancreas, 

 rub it up with well-washed fine sand in a mortar, and 

 digest it with cold water, stirring vigorously. After a time 

 strain through muslin, and then filter through paper. 

 The filtrate has digestive properties chiefly upon starch. 

 Instead of water a more potent solution is obtained by 

 digesting the pancreas at 40 C. for some hours with a 2 

 per cent, solution of sodic carbonate. To prevent the putre- 

 factive changes which are so apt to occur in all pancreatic 

 fluids, add a little 10 per cent, alcoholic solution of thymol. 



(b.) Make a glycerin extract of the pancreas in the same 

 way as described for the stomach (Lesson VII., 1, b.) 

 Before putting it in glycerin it is well to place it for two 

 days in absolute alcohol to remove all the water. This 

 extract acts on starch and proteids. 



(c.) For most experiments it is more convenient to use 

 the excellent pancreatic extracts now supplied by Mr. Benger, 

 of Manchester, as "Liquor Pancreaticus," or those of 

 Messrs. Savory & Moore, or Burroughs, Wellcome & Co. 



