76 DIGESTION OF FAT. 



the teeth, and when these have carried the subdivision as far as mechanical 

 means can, it is continued by chemical agents. Upon these principles, 

 the pancreatic juice divides starch into lactic acid in duodenal digestion 

 a product which, without difficulty, finds its way at once into the system. 



Besides starch and sugar, there is another group of bodies belonging 

 Digestion of to the class of calorifacient food, which, in the case of carniv- 

 fafc - orous animals, seems to be exclusively employed. The fats 



and oils constitute this group. 



The action of the pancreatic and enteric juices upon these bodies, in 

 bringing them into the condition of an emulsion, has already been stated. 

 That this occurs in the intestine appears from the fact that if the pan- 

 creatic duct be tied, no emulsion forms, and the chyle in the laeteals 

 is limpid instead of being milky. In the rabbit this duct opens much 

 lower in the intestine than the biliary, and it is observed that it is only 

 after the food has passed that point that it becomes emulsioned. The 

 place for pancreatic digestion seems to be very constant in tribes that are 

 far apart in habits of life. Thus, in fishes, the pancreas consists of a cor- 

 onet of coecal tubes, surrounding the pyloric extremity of the intestine, 

 each opening into that organ by a separate mouth. 



The fats reach the duodenum without undergoing any change. There, 

 under the influence of the pancreatic juice, they become subdivided into 

 extremely minute portions, which, absorbed by the laeteals, give to the 

 chyle its characteristic aspect. Beyond this condition of subdivision 

 no other change is thus far impressed, the fat of the laeteals being abso- 

 lutely the same as that of the chyme. To the introduction of fat into 

 the laeteals, the presence of bile seems to be necessary, or, if not absolute- 

 ly necessary, absorption is greatly facilitated by it. 



The gastric and pancreatic juices stand in a remarkable relation to one 

 Bernard's doc ano ^ ner the former being an acid liquid, having the power 

 trine of the ef- of bringing into a state of solution nitrogenized bodies, such 

 and alkalinity as ^ Tm 5 tne latter alkaline, without action on nitrogenized 

 in the digest- bodies, but operating energetically on starch, sugar, and oils. 



J U1< From this it might be supposed that the intrinsic qualities of 



these juices are different, and that they act in this manner because of a 

 special dissimilarity of constitution. 



Attempts have been made to prove that this difference of action de- 

 pends wholly on the chemical relations of the juice itself. If pancreatic 

 juice or saliva be purposely acidulated with hydrochloric acid, it is said 

 that it loses at once the power of acting on calorifacient food, but can 

 bring about the solution of the histogenetic. On the other hand, if gas- 

 tric juice be rendered alkaline by admixture with soda, it no longer dis- 

 solves fibrin or coagulated albumen, but gains the power of acting on 

 starch and sugar. Since, then, it thus appears that the same organic body 



