REACTION OF LYMPHATIC ENDOTHELIUM 423 



jecting globules of paraffin oil, a substance whose only action 

 could be mechanical, have been published (5). Small globules 

 of the paraffin oil, injected subcutaneously into the fin, were 

 found to exert no influence on mesenchyme cell, blood vessel 

 or lymphatic endothelium. A transient gathering of leucocytes 

 (sometimes only five or six of these) which always subsided 

 three or four days after the injection, was the only observable 

 tissue response. The globules had not diminished in size after 

 two weeks of observation. 



On another occasion, a few granules of India ink were in- 

 jected into the tail-fin and the result observed under the com- 

 pound microscope. In this case, the carbon granules were 

 taken up by the processes of the connective tissue cells and by 

 lei oocytes, and four or five hours after the injection, most of the 

 granules had been disposed of in this way. This experiment, 

 the details of which will be published elsewhere, showed that the 

 ordinary connective tissue cells, in the tadpole's tail, possess a 

 phagocj^tic power toward carbon granules which is not shared by 

 blood-vessel or lynlphatic endothelium. 



For the present experiments, which were carried out in the 

 spring of 1916, we selected fat, in various forms, as a substance 

 which might conceivably exert an attraction on lymphatic en- 

 dothelium. This was suggested by the presence of an extremely 

 rich lymphatic supply to the intestine of adult vertebrates and 

 of the association of these vessels with fat absorption, and also 

 because certain analyses of lymph, collected from lymphatics 

 draining the leg, have shown a decidedly higher fat content than 

 that of the blood plasma. It was also suggested because of the 

 fact that fat globules can be clearly seen and any diminution in 

 their size easily noted. 



MATERIAL AND METHOD 



The tadpoles, used for these studies, were the larvae of Rana 

 pipiens. The substances, selected for injection, were olive oil, 

 oleic acid, cream and yolk of egg. The tadpoles were anaes- 

 thetized in chloretone (1 to 3000) and a small amount of the 



