166 II. DIGESTION AND ABSORPTION OF FATS 



lower order. For example, Eckstein, 775 working with anesthetized dogs, 

 was able to account for only 21% of ingested olive oil in the thoracic duct 

 lymph in twelve hours, or 17% in a six-hour period. The recoveries were 

 still less when oleic or palmitic acid was fed in the form of the free acid. 

 Eckstein pointed out that the fat absorption would probably have been 

 better under normal conditions if anesthesia had been avoided. Little 

 and Robinson 776 reported quite similar low recoveries in thoracic lymph 

 after fat feeding in the case of dogs. 



Bloom and his associates 777 recently reported a series of experiments on 

 rats which were fed palmitic acid containing C 14 in the carboxyl group. 

 The lymph was collected from the unanesthetized animals by means of a 

 new technic devised by Bollman, Cain, and Grindlay 618 for collecting lymph 

 from the thoracic duct or intestinal lymphatics. When palmitic acid was 

 fed as the triglyceride, or as the free acid, 70 to 92% of the absorbed fatty 

 acid was recovered from the thoracic duct lymph in nineteen to twenty-four 

 hours in nine of the ten tests, while 69 to 84% of the absorbed palmitic 

 acid-C 14 was accounted for in the intestinal lymph. 777 This is by far the 

 largest proportion of fat which has been proved to be transported by the 

 lymphatic pathway. 



It is possible that the palmitic acid-C 14 not recovered may have traveled 

 via the portal vein. However, Bloom et al. 777 call attention to the possi- 

 bility that additional amounts of the fatty acid over and above that re- 

 covered from the intestinal or thoracic fistulas may have entered the lym- 

 phatic circulation in the intestine, to be subsequently lost to the systemic 

 circulation by lymphatic-venous anastomoses. Although such anasto- 

 moses were first described over forty years ago, 778-780 their role in fat trans- 

 port has never been investigated. 



The fact that small amounts of fat containing C 14 were shown to be pres- 

 ent in the liver of rats in which thoracic duct cannulas had been continu- 

 ously present indicates some absorption of this foodstuff by the portal 

 system ; however, the findings have not disproved the hypothesis that the 

 tagged fat found in the fiver may represent material absorbed into the lym- 

 phatic system which has reached the systemic circulation via the lymphatic- 

 venous anastomoses. 



776 H. C. Eckstein, J. Biol. Chem., 62, 743-757 (1925). 



776 J. M. Little and C. S. Robinson, Am. J. Physiol, 134, 773-780 (1941). 



777 B. Bloom, I. L. Chaikoff, W. O. Reinhardt, C. Entenman, and W. G. Dauben, J. 

 Biol. Chem., 184, 1-8 (1950). 



778 F. C. Lea, Bull. Johns Hapkins Hosp., 33, 21-31 (1922). 



779 T. T. Job, Am. J. Anal, 24, 467-491 (1918). 



780 C. F. Silvester, Am. J. AnaL, 12, 447-471 (1912). 



