NORMAL FAT METABOLISM 195. 



the chyle but always the glycerol triesters of the fatty acids involved. The 

 presence of the glycerids in the chyle presupposed a splitting of the esters 

 fed and a synthesis of the fatty acids with glycerol which if not supplied 

 with the fatty acids by the experimenter must have been furnished by the 

 organism. Further details on this interesting point have been furnished in 

 recent work by Bang (a) (1918), who found that fatty acids alone pro- 

 duced but little lipemia while when these are fed with glycerol there is 

 marked lipemia, indicating that the ability of the organism to supply gly- 

 cerol is limited. One experiment which he reported in which he fed 59 

 grams of fatty acid to a dog and recovered only 2 grams in the chyle would 

 indicate that absorption in this case was directly into the blood. 



Direct evidence against the absorption of fat in emulsified form has 

 also been forthcoming. Connstein, experimenting with lanolin, a wax 

 which emulsifies well with water and has a melting point (40-42 C.) 

 only slightly above body temperature, showed that when this substance 

 was fed about 98 per cent of it could be recovered in the feces, showing 

 that neither emulsifying power nor melting point was the criterion for 

 absorption. The same fact was more strikingly shown by Henriques and 

 Hansen, who dissolved vaselin in lard and fed the well emulsified 

 mixture to rats and were able to recover practically all (98 per cent) of 

 the vaselin fed while the lard was completely absorbed. The com- 

 panion test to this one the attempt to recover the substance from the 

 chyle was carried out by Bloor (a) (1913) with negative results. In this 

 experiment a liquid paraffin was dissolved in olive oil, the whole well emul- 

 sified and fed, to dogs. A suitable time after the feeding chyle was collected 

 from the thoracic duct, the contained fat extracted and examined for the 

 paraffin oil. None was found. Thus though all conditions were favorable 

 for the absorption of unchanged emulsion which would have included the 

 mineral oil, no trace of it could be demonstrated while the food fat was 

 completely absorbed. Summing up all the evidence then, the hypothesis 

 of Kiihne appears to be very well supported. Facilities are provided 

 for complete splitting of the fats in the intestine, fatty acids and soaps 

 are absorbed and appear in the chyle as triglycerids, esters of the fatty 

 acids which are hydrolyzable by the intestinal Upases are absorbed but 

 always as triglycerids, while non-hydrolyzable esters of the fatty acids 

 and other fat-like substances which cannot be made water soluble are 

 rejected. Altogether it seems likely that fats are no exception to the rule 

 that substances pass from the intestine only in water solution, and since 

 solubility in water appears to be a necessary prerequisite for use in living 

 cells the intestine acts as a barrier against the admission of substances 

 that cannot be made soluble. The fact that fats appear in the blood 

 stream largely in the insoluble suspended form is probably only an 

 apparent exception since they are readily and quickly transformed in the 

 blood into soluble phospholipoid. 



