150 PHYSIOLOGY OF ALIMENTATION. 



are to-day acquainted with the presence of lipase in a large 

 variety of plant -cells, it is interesting that the discovery of 

 lipase was originally made in experiments on the physiology 

 of the pancreas. This organ contains large quantities of the 

 ferment, but it is well to remember that lipase is one of the 

 most widely distributed enzymes in the animal organism, oc- 

 curring in practically every organ of the mammal. The liver, 

 the stomach, the small intestine, the kidneys, the subcuta- 

 neous tissues, the mammary glands, the blood, and the lymph, 

 all contain lipase. ^ 



The fats of greatest physiological importance are all of 

 them esters of the triatomic alcohol glycerine with palmitic, 

 stearic, or oleic acids. These fats (known as palmitin, stearin, 

 and olein) take up water under the influence of lipase and 

 split into glycerine and fatty acid. A quantitative deter- 

 mination of the activity of a lipase may therefore be made 

 by ascertaining the amount of acid that is formed. Quali- 

 tatively the formation of the acid can be readily demon- 

 strated by the addition of an indicator to a mixture of fat and 

 lipase. 



In laboratory studies with lipase, palmitin, stearin, and 

 olein are comparatively little used. Other esters are acted 

 upon more rapidly by the ferment, so that this property, in 

 addition to their ready solubility in water, renders them more 

 suitable for study. In this way monobutyrin, ethyl butyrate, 

 etc., have come to be extensively used. 



Pure preparations of lipase have never been obtained. 

 The best rapidly lose in strength in the course of a few days, 

 even when most carefully protected. Ordinarily, simple 

 aqueous or NaCl-solution extracts are made of entirely fresh 

 organs which are minced and ground up in a mortar with 

 quartz sand. These extracts are then used for experimental 

 purposes. Glycerine extracts have also been prepared. 



Lipase is, in the presence of water, exceedingly sensitive 

 to comparatively low temperatures. When dry, the lipase 

 from the castor-oil bean will stand a temperature above 100 C. 



