ACTION OF THE ENZYMES OF PANCREATIC JUICE S3? 



it will not work in the presence of free acid. It therefore differs from pepsin 

 in being able to act without the aid of any other substance than water. In 

 the process of tryptic digestion, proteid matter does not swell up at first, but 

 seems to be corroded at once. 



Amylopsin. Starch is converted into maltose in an exactly similar manner 

 to that which happens with saliva, erythro-dextrin and one or more achroo- 

 dextrins being the intermediate products. The amylolytic enzyme of the 

 pancreatic juice, which cannot be distinguished from ptyalin, is called amyl- 

 opsin. The maltose thus formed is converted to dextrose by the maltase, 

 in which form it is ultimately absorbed. 



Pancreatic juice, according to certain observers, possesses the property 

 of curdling milk. It contains a special ferment, rennin, for that purpose. 

 The ferment is distinct from trypsin, and will act in the presence of an acid 

 (W. Roberts). The milk-curdling ferment of the pancreas is, in some pan- 

 creatic extracts, said to be quite powerful, insomuch that i c.c. of a brine ex- 

 tract will coagulate 50 c.c. of milk in a minute or two. 



Steapsin or Lipase. Oils and fats are emulsified and saponified by the pan- 

 creatic secretion. The terms emulsification and saponification may need a 

 little explanation. The former is used to signify an important mechanical 

 change in oils or fats, whereby they are made into an emulsion, or in other 

 words are minutely subdivided into small particles. If a small drop of an 

 emulsion be looked at under the microscope it will be seen to be made up of 

 an immense number of minute rounded particles of oil or fat, of varying 

 sizes. The more complete the emulsion the smaller are these particles. An 

 emulsion is formed at once if oil or fat, which when old is slightly acid from the 

 presence of free fatty acid, is mixed with an alkaline solution. Saponification 

 signifies a distinct chemical change in the composition of oils and fats. An 

 oil or a fat being made up chemically of glycerin, a triatomic alcohol, and 

 one or more fatty-acid radicles, when an alkali (potassium hydrate) is added 

 to it and heat is applied, two changes take place : first, the oil or fat is split up 

 into glycerin and its corresponding fatty acid ; second the fatty acid combines 

 with the alkali to form a soap which is chemically known as stearate, oleate, 

 or palmitate of potassium. Saponification thus means a chemical splitting 

 up of oils or fats into new compounds, and emulsification means merely a 

 mechanical splitting up into minute particles. The pancreatic juice has been 

 for many years credited with the possession of a special ferment, which was 

 called by Claude Bernard steapsin, and which is a lipase or fat-splitting fer- 

 ment. This ferment has not been isolated, but its presence may be demon- 

 strated by adding portions of the fresh pancreas to butter or other fat and 

 maintaining the proper temperature. Its action is made manifest by the libera- 

 tion of butyric acid, which smells like rancid butter. 



The generally accepted theory is that only a small portion of the fat which 

 is eaten is thus changed into soap, and that the function of the saponified fat 

 22 



