FAT METABOLISM 



The chemical theory of Pa1 absorption further explains why there should 

 be such large quantities of soapy substances in the intestinal contents, 

 and also why the globules of fat presenl in the epithelial cells of the 

 intestine are so very much Smaller than those which lie on the surfi 

 the epithelium. 



It mighl be objected to the conclusions just stated that, although unde- 

 tectable, there is really some essential physical difference between emul- 

 sified fat and emulsified hydrocarbon. En order entirely to prove tl 

 for the chemical theory, ii is necessary to feed a neutral fal | sing 

 some characteristic thai depends on the manner of union existing between 

 fatty acid and glycerine, and then to see whether it appears in an un- 

 changed idition in the thoracic duct. It" it does so, the fat must hi 



been absorbed through the intestinal epithelium in an unbroken, unsapon- 

 ified condition, for it is unlikely that, in the resynthesis which occurs in 

 the intestinal epithelium, the fatty-acid molecules would reeombine with 

 the glycerine molecules in exactly the same manner as before. 



There are, however, bul very \'rw qualities of neutral fats, apart from 

 those of the fatty acids which compose them, by which they can be char- 

 acterized. The most likely one is that of optical activity. None of the 

 ordinary fats is optically active, although from chemical considerations 



it is quite < ceivable that Borne should be so. in order to obtain such a 



fal Bloor" conducted numerous experiments with the esters of stearic 

 acid.* In a series of experiments Bloor fed isomannid-dilaurate, a syn- 

 thetic fat of dextrorotatory power and as readily absorbed as natural fats, 

 and by examination of the neutral fal present in the chyle flowing from 

 the thoracic duct, found no evidence of the dextrorotatory fat. This 

 confirms previous work by Frank, who found thai the ethyl esters of 

 tany acids are nol absorbed unchanged. The results tl \' both workers 

 emphasize the probability thai readily Baponifiable fatty-acid i si s <1" 

 not escape saponification under the favorable conditions of the normal 

 intestine. In other words, had the fats been absorbed unchanged, 

 would be required by the mechanistic theory of fal absorption, they 



would have appeared in the chyle in optically active conditions. 

 These m08l important conclusions lead us to inqliit. a to 



for the changi in fat during its absorption. It can nol be for the pur] 

 of preventing the absorption of undesirable fatty substai es, s as the 

 petroleum hydrocarbons or the wool fats, because such substanc 

 so rarely presenl in our food. It is most probable that the breakdo 



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