278 THE DIGESTION OF FAT 



emulsified fat is given. Over-acidity of the gastric juice lowers the 

 action of this lipase. The ferment can be extracted from the 

 mucosa by glycerine, and is then very susceptible to the action of 

 alkali. This susceptibility is not observed in the case of gastric 

 juice, so that probably a zymogen exists in one case and the 

 enzyme in the other. As in the case of other ferments, the pro- 

 ducts of its action are in proportion to the square root of the 

 amount of enzyme present, and of the length of the period of 

 reaction. The bile contains no lipase. 



In 1834 Eberle recognised that pancreatic juice had the power 

 of emulsifying fat. Cl. Bernard discovered that it set up an 

 acid reaction in fat, and Berthelot at Bernard's request tested 

 the action of the juice both upon mono-butyrin and on neutral 

 fat. In both cases he obtained fatty acids. Many later workers 

 failed to obtain results owing to the sensitiveness of the ferment, 

 which renders manipulation difficult. It is soluble neither in 

 water nor in glycerine, so either pancreatic juice or minced gland 

 must be used. With either of these it is easy to obtain 

 rapid decomposition of either fluid or solid fats. The ferment 

 works best in weak alkali; it is harmed either by strong alkali 

 or acid. A mixture of bile and pancreatic juice will split 3| 

 times more fat than the juice alone. Macerated pig's pancreas 

 split no less than 86-4 per cent, of the fat of milk in 24 

 hours (Fr. Mtiller). The modern view of fat absorption is that 

 no neutral fat is absorbed, but all split and brought into com- 

 plete solution. The pancreatic lipase is sufficiently powerful to 

 effect the decomposition. 



Pawlow determined that taking of fat excites the secretion 

 of pancreatic juice, and increases the amount of lipase in the 

 juice. Thus the first two hours after the taking of milk a juice 

 relatively rich in lipase is secreted, while if fat-free milk be fed 

 an equal volume of juice is secreted, but the amount of lipase is 

 markedly lessened. No lipase has been obtained either from the 

 mucosa of the intestine or from the chyle. By the action of the 

 gastric and pancreatic Upases the neutral fat is split into glycerine 

 and fatty acids. Some of the latter unite with the alkali of the 

 pancreatic and intestinal juice and form soaps. The fatty acids 

 are entirely insoluble in water, while the sodium soaps are only 

 slightly soluble. 



The bile has a dual function" as 1 a solvent. Firstly, it 



