172 A Manual of Veterinary Physiology. 



Fats are chemically neutral, but if rancid they are acid ; 

 if carbonate of soda be added to a fat containing even a 

 small proportion of free fatty acid, the fatty acid unites 

 with the alkali and forms a soap ; this soap envelops the 

 fat globules and a true emulsion results. 



If the fat acted upon be a neutral fat, nothing less than a 

 free alkali, such as caustic potash, can liberate the fatty 

 acids. 



Pancreatic juice, however, can attack perfectly neutral 

 fats, splitting them up into free fatty acids and glycerin, 

 and this it is enabled to do by means of the fat-splitting 

 ferment it contains. 



The most important action on the fat is probably the 

 formation of the minute oil globules or emulsionizing, by 

 which means rapid absorption through the intestinal villi 

 occurs. 



Colin's experiments on horses and other animals, showed 

 that fats were as perfectly absorbed from the intestine in 

 the entire absence of pancreatic juice as in its presence. 

 This is probably due to the alkaline intestinal fluid. 



The ferments of the pancreas which bring about all the 

 changes we have described do not exist ready formed in the 

 gland, but they are formed from a mother-substance termed 

 Trypsinogen, which is manufactured in the cells of the 

 gland. This zymogen by decomposition yields the ferments. 



The changes occurring in the cells of the gland cor- 

 respond very closely with those we have described in the 

 salivary secretion. There is a period of rest during which 

 the gland is rapidly forming the mother-substance of the 

 ferments, which can be seen as minute granules tilling the 

 cells, and there is a period of activity during which the 

 gland is discharging its manufactured products. In the 

 herbivora the gland is practically constantly secreting, but 

 the periods of rest, and activity still occur tor the reason 

 that all the lobes are not active at the same time. 



When a pancreas or lobe of a pancreas has been some time 

 at rest the cells forming it- are rendered very indistinct, the 

 lumen of the alveolus is nearly obliterated by the swollen 



