ADDITIONS AND ;NOTES TO VOL. II. 511 



intestine are continuously permeated with aqueous moisture, and 

 can never be dry at any point, we cannot understand, from a phy- 

 sical point of view, how the oily fat can penetrate these membranes. 

 Hence it has been assumed that the fat is saponified by the alkali 

 of the bile ; but since the greater part of the chyle-fat is unsaponi- 

 fied fat, we are compelled either to withdraw altogether from this 

 hypothesis, or to assume with Moleschott,* that the fat is saponi- 

 fied in the intestine (by means of the pancreatic fluid), but is again 

 liberated in the lymphatics. This latter view, independently of its 

 teleological improbability, can hardly be accepted when we consider 

 that after the use of fatty food, mere traces of fatty acids are found 

 in the intestinal canal, that un saponified fat is recognisable even in 

 the epithelium and cells of the villi, and that, according to 

 Schmidt's experiments, the exclusion of the bile renders the chyle 

 very deficient in free fat, while it does not affect its quantity of 

 fatty acids. Lastly, the bile possesses so very slight a solvent 

 power (none whatever, according to Bidder and Schmidt) for neutral 

 fats (and even for the fatty acids it would appear from the experi- 

 ments of Lenz, not to be very considerable), that the bile which is 

 secreted would be perfectly insufficient to dissolve the whole of 

 the fat which is resorbed. It has been consequently supposed 

 that individual parts of the inner intestinal surface may be spe- 

 cially capable of absorbing fat, and that fat alone can penetrate 

 through them; but in that case the assistance of the bile in the 

 resorption of the fat would appear to be altogether superfluous. 

 But since the bile has been shown to be necessary to this object, 

 nothing in fact remains but to assume that the bile induces a modi- 

 fication in the relations of adhesion between the oleaginous fluid and 

 the moist watery membranes, by which the transmission of the fat 

 through these membranes is effected. The theory of the physical 

 relations of different kinds of fluids to different membranes has 

 been as yet so little studied, that such an assumption as the above 

 is by no means inadmissible; indeed we find that Bidder and 

 Schmidt performed an experiment which indicates with toler- 

 able distinctness the existence of such a relation ; they plunged two 

 glass capillary tubes in oil, having previously moistened the interior 

 of one of them with bile ; the oil rose far higher in the tube mois- 

 tened with bile than in the other, either when it was perfectly dry 

 or when moistened with a saline solution. This mode of explaining 

 the absorption of fat has been established beyond all doubt by the 



* Physiologic des Stoffwechscls Erlangen, 1851, S. 209. 



