METHODS FOR STUDY OF FAT ABSORPTION 129 



Moreover, it is known that a proportionality exists between the body sur- 

 face area and that of the intestine. Since the rate of absorption must be a 

 function of the available area of the small intestine, it is only logical that 

 any biometric measurement related to this value would be useful in the 

 correlation of such data on fat absorption. 



Deuel, Hallman, and Leonard 614 have compared the results on absorption 

 of margarine fat when fed at a standard dosage to adult male rats (Group 1 ) 

 and to adult female rats (Group 4) ', also, at a standard dosage, to young 

 males (Group 2) and young females (Group 5) ; and at a high dosage to 

 young males (Group 8). The results are graphically illustrated in Figures 

 10 and 11, in which the rate of absorption is compared by several procedures. 



On the basis of the above tests, it would seem quite definite that the most 

 constant results can be obtained with animals of varying size if the rate of 

 absorption is expressed on the basis of milligrams absorbed per 100 sq. cm. 

 of body surface per hour. This procedure has been used in the tests on 

 absorption referred to in a later section. It has also been the usual practice 

 to feed the fat in such tests on the basis of surface area (usually in a dosage 

 of 300 mg. per 100 sq. cm.). 



(3) Other Methods for the Study of Fat Absorption 



In addition to the direct method of estimating fat absorption by analysis 

 of the gastrointestinal contents, a number of indirect procedures have been 

 employed. As mentioned earlier, such methods have the advantage of 

 giving data on the pathways of absorption and the form in which the sub- 

 stances are carried to the tissues. 



a. Cannulation of the Thoracic Duct. The most important procedure 

 for the study of fat absorption involves the cannulation of the thoracic duct. 

 Since a large portion of the fatty substances travel via the lymphatic route 

 from the intestine, a collection of this lymph before it is poured into the 

 blood stream will furnish a qualitative as well as a rough quantitative 

 method for following fat absorption. It is a relatively simple operative 

 procedure to introduce a cannula into the thoracic duct. While the amount 

 of lymph passed into the blood stream via this route is small in the fasted 

 animal, the quantity is immediately increased, in a large measure, within a 

 few hours after a fatty meal has been ingested. The lymph becomes milky 

 from the fat globules; it is then referred to as chyle. Such lymph may 

 contain as much as 5 to 15% of emulsified fat. Some criticism has been 

 directed at experiments in which studies have been made on thoracic 

 lymph, since this represents lymph not only from the intestinal area but 

 also from other organs. 



