ACTION OF THE PANCREATIC JUICE IN DIGESTION. 273 



Unlike the gastric juice, the secretion of the pancreas, under ordinary conditions of 

 heat and moisture, rapidly undergoes decomposition. In warm and stormy weather, the 

 alteration is marked in a few hours; but, at a temperature of from 50 to 70 Fahr., it 

 decomposes gradually in from two to three days. The changes which the fluid thus 

 undergoes are interesting, from the fact that some physiologists, having experimented 

 with an altered or an abnormal secretion, have failed to recognize certain of the charac- 

 teristic properties of the normal fluid. As it thus undergoes decomposition, the fluid 

 acquires a very offensive, putrefactive odor, and its coagulability diminishes, until finally 

 it is not affected by heat. The alkalinity, however, increases in intensity ; and, when 

 neutralized with an acid, there is a considerable evolution of carbonic acid, which does 

 not occur in fresh pancreatic juice. 



Action of the Pancreatic Juice in Digestion. 



It is only since the observations of Bernard, in 1848, that the pancreatic juice has been 

 regarded as a fluid of any great importance in digestion. It has now been demonstrated, 

 both by cases of disorganization of the pancreas in man and by experiments on animals 

 in which the tissue of the organ has been destroyed, that the pancreatic juice is essential 

 to digestion and to life, animals dying of inanition when its function has been abolished. 



The most striking feature in the discovery made by Bernard was the action of the 

 pancreatic juice in the digestion of fats; it being shown that these principles are acted 

 upon almost exclusively by the pancreas, and that they pass through the alimentary canal 

 undigested when this organ has been destroyed. For this reason, probably, the action 

 of the pancreas in the digestion of fatty substances has received an undue prominence ; 

 and its action upon other articles of food, though not at the present day overlooked, does 

 not always receive proper consideration. We shall find that the pancreatic juice has an 

 important action in the digestion of nearly all the alimentary principles as they pass out 

 from the stomach. 



Action upon Fats. Even before the publication of Bernard's researches, it was pretty 

 generally admitted that the digestion of fat consisted in its minute subdivision and sus- 

 pension in the form of an emulsion. This view was adopted from the fact that, during 

 the absorption of fats from the intestinal canal, the lacteals and thoracic duct always 

 contain innumerable small, fatty globules ; but the ideas of physiologists as to the par- 

 ticular fluid by which the emulsification of fats is accomplished were not very well 

 settled. The most generally-received opinion, however, was that this was effected by 

 the bile ; but experiments on this subject were very contradictory. 



One of the most remarkable facts observed by Bernard was that, in the rabbit, after 

 the ingestion of fatty matters, vessels filled with white chyle do not make their appearance 

 at the commencement of the small intestine, as in other animals, but are first seen from 

 twelve to twenty inches below the pylorus. The anatomical peculiarity in these animals 

 is that the pancreatic duct, instead of opening into the intestine with the bile-duct at the 

 upper part of the small intestine, has its opening from twelve or twenty inches below, 

 just at the point where the chyliferous vessels are observed. This fact, which we have 

 frequently confirmed, points directly to the pancreatic juice as the agent principally, if 

 not exclusively, concerned in emulsifying the fats; while it shows that the bile possesses 

 little or no immediate efficiency in this regard. Following out this line of inquiry, and 

 operating with fresh, coagulable pancreatic juice and the liquid fats or those capable of 

 being liquefied by gentle heat, it was found that slight agitation of this fluid with the fats 

 produced a very fine and permanent emulsion, similar in every respect to the milky fluid 

 found in the lactenls during digestion. In fact, comparative analyses of the lymph and 

 chyle have shown that the latter liquid is nothing more than lymph with the addition of 

 fatty emulsion. As soon as the absorption of fat is completed, the lacteal vessels lose 

 their opaque, white contents and carry nothing but colorless lymph. This is one of the 

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