288 PHYSIOLOGY OF ALIMENTATION. 



in water. Others are soluble in water if bile is present, and 

 some are soluble in protoplasm. If, therefore, it could be 

 shown that under the conditions which exist in the body it 

 is possible for all the fat of a fatty meal to be converted into 

 digestion products soluble in the body fluids, and this within 

 the time allowed for the absorption of such a meal under 

 physiological conditions, one of the great difficulties in the 

 way of believing that all fat is absorbed only in the form of 

 its soluble digestion products would be overcome. The ex- 

 tent to which the fat of a fatty meal is split into fatty acid and 

 alcohol during an ordinary period of digestion has been greatly 

 underrated by the majority of investigators. We know now 

 from the observations of RACHFORD 1 that in the hours making 

 up the ordinary period of pancreatic activity consequent 

 upon a meal ample time is allowed for the splitting of at 

 least the larger portion, and probably all of the fat consumed 

 in that meal. 



Before entering further into the discussion of this question 

 let us ask first of all whether fat can be absorbed in the form 

 of an emulsion. If this question is answered in the affirma- 

 tive, then we have to ask, Is all the fat absorbed in this form, 

 or only a part of it, and how much? The mere question as 

 to whether fat can be absorbed in the form of an emulsion 

 must, perhaps, be answered in the affirmative. From a 

 physical standpoint the question is one which asks whether 

 substances having a high molecular weight can diffuse through 

 animal membranes. The physical experiment to settle this 

 question has been made by EiJKMANN, 2 who found that a 

 solution of glue poured upon an agar-agar plate will, if a 

 proper temperature- be maintained, soon diffuse into the 

 agar-agar. In this case we have one colloid diffusing into 

 another. The physiological experiment to answer this ques- 

 tion has been made by FmEDENTHAL, 3 who fed colloidal so- 



1 RACHFORD: Journal of Physiology, 1891, Xtl, p. 72. 



2 EIJKMANN: Centralbl. f. Bacteriol., 1901, XXIX, p. 841. 



3 FRIEDENTHAL: Archiv fur (Anat. und) Physiologie, 1902, p. 149. 



