ABSORPTION AND TRANSPORT OF FATS 145 



cases, the fat globules were largely in the inner part of the cells. It is now 

 believed that these two pictures may represent different stages in fat ab- 

 sorption. According to the Schafer concept, fat is carried into the cells by 

 the leucocytes; it is presumably deposited there temporarily, and gradually 

 works its way to the basement membrane of the oell. During its passage 

 through the length of the cells, the large droplets gradually disappear, to be 

 replaced by much finer ones, preliminary to their removal from the cell 

 through the basement membrane. 



In 1888, Heidenhain 689 proposed a slightly modified hypothesis to ex- 

 plain fat absorption. The main difference from the Schafer theory lay in 

 the fact that he ascribed a minor role to the leucocytes in the fat absorption 

 process. Heidenhain cites numerous data to prove that no parallelism 

 exists between the leucocyte population and fat absorption. For example, 

 in newborn puppies, leucocytes are seldom present in the intestinal epi- 

 thelium during active fat absorption, although they are found in large num- 

 bers during fasting. Again, many leucocytes which apparently contain fat 

 are present in the glands of Lieberkuhn ; there is no logical explanation, in- 

 sofar as absorption is concerned, to account for their presence in this area. 

 Finally, granules which stain black with osmic acid may be found in fasting 

 animals, near and within Lieberkiihn's gland. Although osmic acid is 

 generally accepted as a stain which is specific for fat, it has been suggested 

 that some substance, other than fat, accounts for the stained particles 

 found in these experiments. 



The results of Clark and Clark 690 throw further light on the functions of 

 the leucocytes in fat absorption. These workers have confirmed Zawary- 

 kin's findings 691 that leucocytes are present in large numbers in the intestinal 

 mucosa during fat absorption. However, they are only rarely found in the 

 lumen of the intestine, but occur chiefly in the lacteals 692,693 and around the 

 epithelial cells. These data lead one to the conclusion that the leucocytes 

 are not concerned with the first stage in fat absorption, namely, the trans- 

 fer of fat from the lumen of the gut to the epithelial cells. The leucocytes 

 would exert their chief function in the second stage of fat absorption, i.e., 

 the transport of the fats from the epithelial cells to the lacteals. 



Munk, 694,695 in 1884, was more definite in his hypothesis that fat was 



689 R. Heidenhain, Arch. ges. Physiol. (Pfluger's), 43, suppl., 1-103 (1888). 



690 E. R. Clark and E. L. Clark, Am. J. Anat., 21, 421-448 (1917). 



691 T. Zawarykin, Arch. ges. Physiol. (Pfluger's), 31, 231-239 (1883). 

 « 92 T. Zawarykin, Arch. ges. Physiol. (Pfluger's), 85, 145-157 (1885). 

 t9J R. Zipkin, Anal. Hefie, 23, 113-186 (1904). 



694 1. Munk, Ergeb. Physiol., 1, 296-329 (1902). 



695 1. Munk, Arch. -path. Anat. Physiol. (Virchow's), 95, 407-467 (1884). 



