DIGESTION AND ABSORPTION OF HYDROCARBONS 275 



thoracic duct. They were unable to demonstrate the transport of any 

 appreciable quantity by way of the portal venous system. Chaikoff and 

 co-workers 157 were able to account quantitatively for the absorbed chole- 

 sterol in the lymph of rats. Thus, when 3.5 mg. of ring-labeled chole- 

 sterol dissolved in 0.5 ml. of corn oil was given to rats by stomach tube, 

 from 22 to 49% was shown to be absorbed. These workers were able to 

 recover 70 to 90% of that absorbed in lacteal lymph, and 94 to 101% in 

 the thoracic duct lymph. About 50% of the cholesterol in the lymphatics 

 was shown to be esterified. 69,157 It is suggested that the esterification of 

 dietary cholesterol takes place during its passage from the lumen to the 

 site of lymph collection. Swell and collaborators 83 reported that the 

 pancreas is the major source of the cholesterol esterase of the rat intestinal 

 mucosa. 



6. The Digestion and Absorption of Hydrocarbons 



(1) Paraffins 



In all of the earlier work on the absorption of paraffins, the experi- 

 mental data were interpreted to mean that none was absorbed. This 

 conclusion was based upon the ability to recover administered hydro- 

 carbons practically quantitatively from the feces, and also upon the failure 

 to find any trace of such substances in the chyle. Thus, Henriques and 

 Hausen 158 were able to recover 95% of the vaselin administered in a vaselin- 

 lard mixture from the feces of rats. Furthermore, Bloor 159 obtained 85 

 to 100% of the hydrocarbons in the feces after giving a liquid hydrocar- 

 bon mixture, and also vaselin alone or in emulsions in olive or coconut oil. 

 Connstein 160 had earlier reported a quantitative recovery, from the feces 

 of a dog, of 20 g. of lanolin which had previously been fed. However, 

 lanolin consists of sterols and triterpenes, which should not be confused 

 with the aliphatic hydrocarbons. Moreover, Bloor 159 was unable to 

 demonstrate the presence of any absorbed hydrocarbon in the chyle. 

 Clark and Clark 161 and Clark alone 162 reported a similar rejection of hydro- 

 carbons when they were injected into the tails of larvae of the bullfrog 

 (Rana catesbiana) and Fowler's toad (Bufo lentiginosus Fowleri). Fi- 



167 I. L. Chaikoff, B. Bloom, M. D. Siperstein, J. Y. Kiyasu, W. O. Reinhardt, W. G. 

 Dauben, and J. F. Eastham, J. Biol. Chem., 194, 407-412 (1952). 



168 V. Henriques and C. Hausen, Zentr. Physiol, 14, 313-316 (1900). 



169 W. R. Bloor, J. Biol. Chem., 15, 105-117 (1913). 

 180 W. Connstein, Arch. Physiol, 1899, 30-32. 



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



162 E. R. Clark, Anal Record, 10, 191-192 (1915-1916); 11, 1-17 (1916-1917). 



