THE FATS. 295 



will probably regard this mode of explanation as satisfactory. 

 Thus, indeed^ the absorption of fat in certain superficial parts of the 

 villi could be explained ; but not the admixture of fat in their 

 interior, since the fat in the minutest branches of the lacteals is seen 

 to be in a state of extreme comminution, and is mixed with 

 an albuminous fluid. Although the admixture of fat with an 

 aqueous fluid is regarded as impossible upon the surface, yet its 

 possibility is here being assumed where we can no longer make 

 direct observations. All the former attempts to explain the diges- 

 tion and resorption of fat are open to the same objections, since, as 

 we have already mentioned (in vol. ii, pp. 102 and 115), the pro- 

 perty of forming emulsions with oily fat, and, consequently, of pro- 

 moting the resorption of that substance, has been ascribed by some 

 physiologists to the bile, and by others to the pancreatic juice, 

 although we know that the fatty particles of an emulsion very 

 imperfectly, or scarcely at all, penetrate through a moist filter or 

 a moist membrane. It is, however, impossible to deny that the 

 emulsive condition of the fat essentially facilitates its resorption ; 

 the bile may, at all events in association with the pancreatic juice 

 and with the co-operation of the intestinal movements, reduce the 

 fat to a state of emulsion, that is to say, diffuse it in minute particles 

 through the watery fluid ; but this in no degree serves to explain 

 the mechanical process of resorption. Since Bidder and Schmidt 

 first proved by their experiments that bile was unquestionably 

 necessary for the digestion of fat (see note to p. 105 of vol. ii, in the 

 Appendix), von Wistinghausen* has succeeded, under their direc- 

 tions, in discovering the physical conditions under which the 

 resorption of fat occurs. He has ascertained that oil cannot be 

 made to penetrate through animal membranes without considerable 

 pressure, but that it may be forced through with comparative 

 facility when the membrane is saturated with a fluid which adheres 

 to, or has an affinity for oil. When the membrane was moistened 

 with a solution of potash, an abundance of saponified oil appeared 

 on this side of the membrane in the course of 10 hours, under the 

 pressure of a column of mercury of from 1*75 to 3*37 millemetres 

 [or from *068 to '132 of an inch], and associated with it was free 

 fat which had been mechanically borne along by the soap. When 

 a mixture of equal parts of potash-ley and albumen was employed, 

 the oil passed through the membrane even without pressure, 

 although in very small quantity, while in this case also a soap was 

 formed. The oil, however, passed through animal membranes, 

 * Diss. inaug. Dorp. Livon. 1801. 



