ABSORPTION AND TRANSPORT OF FATS 165 



ference of fat droplets from the cells to the interior of the villi. It is be- 

 lieved that this is accomplished by pumping movements produced by 

 lengthening and shortening of the musculature. 770 Within the villus, the 

 fat remains in relatively coarse globules, and it does not form the dust-like 

 particles until it reaches the chyle. 



(c) Hydrolysis-Resynthesis Theory of Loevenhart. 771 According to this 

 hypothesis, fat is hydrolyzed whenever it passes in or out of the intestinal 

 cells. It is assumed that, wherever the fat globules are required to pass 

 through a cell membrane, similar hydrolysis and resynthesis occur. 

 Loevenhart based his theory upon the fact that lipase is found to be widely 

 distributed in all tissues, especially in those which are most concerned in fat 

 metabolism. However, there is some question as to whether lipase or 

 esterase was the enzyme studied by this worker, as the substrate employed 

 was ethyl butyrate. 772,773 Moreover, Bradley 774 was unable to confirm 

 Loevenhart's demonstration of lipases in the mammary tissues and in fat 

 depots. 



(4) The Transport of Fat to the Liver and Tissues 



There are two pathways by which fat may be transported from the intes- 

 tine to the liver and tissues. One of these routes is by way of the lacteals, 

 the intestinal lymphatics, and the thoracic duct into the blood stream. 

 The second pathway originates in the capillary network in each villus, from 

 which the fat ultimately reaches the liver by way of the portal circulation. 

 Although this latter route is presumably of limited importance insofar as 

 fat is concerned, it is of major significance in the transport of water-soluble 

 substances to the body tissues. Accurate methods have not been available 

 until recently to trace the course of fat after absorption ; however, the use of 

 fat having fatty acids tagged with radiocarbon has apparently rendered 

 possible a much more quantitative evaluation than was possible before 

 this technic was employed. 



a. The Transport of Fat in the Lymph. In the classical experiments of 

 Munk and Rosenstein, 620 which were carried out on a patient suffering from 

 elephantiasis who developed a lymphatic fistula in the left leg, it was pos- 

 sible to account for only 60% of the ingested fat in the lymph. The re- 

 coveries of ingested fat reported by later investigators have been of a much 



770 F. Verzar, Ergeb. Physiol, 32, 391-471 (1931). 



771 A. S. Loevenhart, Am. J. Physiol, 6, 331-350 (1901-1902). 



772 M. Arthus, J. physiol. path, gin., ■'+, 455-461 (1902). 



773 C. Foa, Arch. ital. bid., 63, 229-238, 239-258 (1915). 



77 *< H. C. Bradley, J. Biol. Chem., 13, 407-418, 431-439 (1913). 



