292 DIGESTION. 



acid reaction in the jejunum and ileum, which remains for three or 

 four hours after the injection of the sugar. 



Vegetable mucus (Bassorin) was made the subject of several 

 experiments by Frerichs,* who found that during the process of 

 digestion, at all events the greater part of it was not altered, and 

 reappeared unchanged with the excrements. [Gum tragacanth, in 

 which bassorin exists abundantly, was the substance actually 

 experimented upon by Frerichs. G. E. D.] 



Like Blondlot, Frerichs convinced himself that vegetable jelly 

 (pectin, and its derivatives) is totally unaffected by the digestive 

 fluids. 



No group of nutrient matters has presented so many difficulties 

 to physiologists as that of the/ate, and even in the present day we 

 must not flatter ourselves that we perfectly understand the process 

 of their digestion. 



We shall, in the first place, notice the successive changes which 

 may be perceived to take place in the fat in its passage from the 

 mouth downwards in the different parts of the intestinal tract. We 

 could scarcely expect to observe any changes in the fat while in the 

 mouth and in the stomach ; for we have already seen that both the 

 saliva and the gastric juice are devoid of any influence either of a 

 mechanical or chemical nature upon it ; and in point of fact, we 

 find on examining the contents of the stomach after the use of fat 

 (whether it has been taken alone or in conjunction with other sub- 

 stances), that the fat itself has not undergone the slightest change. 

 Every physiologist, moreover, coincides in this point, that the 

 digestion of fat commences in the duodenum. 



In the duodenum, and still more in its further course along 

 the small intestine, we find that the fat ceases to appear in large 

 drops or semifluid masses ; the further we descend in the small 

 intestine, so much the smaller do we find these drops becoming, 

 till at length the fat appears very finely comminuted, and the 

 chyme presents an emulsive appearance. Since we see the lacteals 

 distended with white (fatty) chyle after the use of fatty food, it is 

 obvious that the principal course by which the fat makes its way 

 into the blood is through the lymphatics of the intestinal walls. 

 If, however, we follow this fat, which is easily recognisable with 

 the microscope, in its course from the cavity of the intestine to the 

 finest branches of the lacteals in the villi, we find that notwith- 

 standing repeated rinsings with water, fat-globules may be per- 

 ceived at intervals on and between them, which, however, only 

 * Handworterbuch der Physiologic. Bd. 3, Abt. 1, S. 807. 



