126 II. DIGESTION AND ABSORPTION OF FATS 



drawn into the fistula by the peristaltic movements. Fluids can be intro- 

 duced and recovered quantitatively. Figure 9 gives a representation of 

 this type of fistula. Although most of the earlier fistulas have been adapted 

 only to dogs, Johnston 606 states that the new procedure is suitable for any 

 animal, when loop studies are desired. 



{0) Cori Technic 



The most physiological procedure, and obviously the one which should 

 give the closest approximation to that normally taking place in the gastro- 

 intestinal tract, involves the use of unoperated, unanesthetized rats. 

 Such prerequisites are met in the technic which was first employed by Cori 607 

 for the study of the rate of absorption of sugars from the gastrointestinal 

 tract of rats. The same procedure was used later by this investigator for 

 amino acids, 608 for lactic acid, 609 and for ethyl alcohol. 610 In the Cori pro- 

 cedure, accurately measured amounts of solutions of the substances under 

 investigation are given by stomach tube to unanesthetized, fasted rats. 

 The animals are sacrificed after several time intervals, the gastrointestinal 

 tract is removed intact, and the amount of the component under study still 

 remaining in the gut is determined by analysis. The difference between 

 the amount fed and the amount recovered represents that absorbed during 

 the interval under study. Corrections must usually be applied to the 

 analyses of the intestinal contents based upon blank values obtained with 

 control rats, which are fasted for the same intervals but which are given no 

 supplements. Care should be taken to avoid frightening the animals, as this 

 may influence the emptying time of the stomach as well as the intestinal 

 movements. Any such variations will obviously have the greatest in- 

 fluence on experiments of short duration. When the animals will eat 

 spontaneously, some of these difficulties may be avoided, but the time of 

 ingestion of the food cannot be established with as much precision as when 

 the material is given by stomach tube. In order to obtain consistent re- 

 sults, it is important that the animals be of the same stock, age, weight, and 

 also the same sex. Cori expressed the absorption in terms of the absorption 

 coefficient, which is the number of milligrams of the substance absorbed per 

 100 g. of body weight per hour. Modifications of the Cori technic have 

 been employed in the study of the absorption of fats and fatty acids, by 

 Irwin, Steenbock, and Templin, 611 and by Deuel, Hallman, and Quon. 612 



807 C. F. Cori, J. Biol. Chem., 66, 691-715 (1925). 



808 C. F. Cori, Proc. Soc. Exptl. Biol. Med., 24, 125-12(5 (1926). 



809 G. T. Cori, J. Biol. Chem., 87, 13-18 (1930). 



810 C. F. Cori, E. F. Villiaume, and G. T. Cori, ./. Biol. Chem., 87, 19-25 (1930). 



