ABSORPTION OF FATS AND INSOLUBLE SUBSTANCES. 289 



during the digestion of fat, as contrasted with the epithelium observed dur- 

 ing the intervals of digestion, showing the cells, during absorption, filled with 

 fatty granules. 



It has not been demonstrated exactly how the fatty particles penetrate the 

 epithelium of the villi, but the fact of such penetration is undoubted. From 

 the epithelium, the particles of emulsion 

 pass into the substance of the villi 

 probably into the lymph-spaces and ca- 

 nals and from these they readily find 

 their way into the lymphatic capillaries. 

 It has been shown that fatty emulsion 

 will pass more easily through porous 

 septa that have been moistened with 

 bile; and it is probably in this way 

 mainly that the bile aids in the passage 

 of the fine particles of fat into the lac- 

 teals. 



As a general law, insoluble substan- 

 ces, with the exception of the fats, are 

 never regularly absorbed, no matter how 

 finely they may be divided. The appar- 

 ent exceptions to this are mercury in a state of minute subdivision like 

 an emulsion, and carbonaceous particles. As regards mercury, it is well 

 known that minute particles in the form of unguents may be introduced into 

 the system by prolonged frictions ; but this can not be taken as an instance 

 of physiological absorption. The passage of small, carbonaceous particles 

 through the pulmonary membrane seems to be purely mechanical. The same 

 thing may possibly occur when fine, sharp particles of carbon are introduced 



FIG. 94. Epithelium of the small intestine of 

 the rabbit (Funke). 



FIG. 95. Epithelium from the duodenum of a 

 rabbit, two hours after having been fed 

 with melted butter (Funke). 



FIG. 96. Villi filled with fat, from the small 

 intestine of an executed criminal, one hour 

 after death (Funke); 



into the alimentary canal ; but the experiments of Mialhe with pulverized 

 charcoal, and particularly those of Berard, Robin and Bernard with lamp- 



