REACTION OF LYMPHATIC ENDOTHELIUM 431 



fifteen minutes to half an hour or more in close contact with the 

 tip or wall of the lymphatic, the leucocyte would move away 

 again. Shortly before or at the time of wandering away, the 

 leucocj^te lost its brown pigment and became clear (fig. 7). 



The mesenchyme cells, just as in the case of the olive oil, 

 remained totally indifferent to the presence of the injected sub- 

 stance. In no instance did the blood-vessel endothelium re- 

 spond to the fatty acid or soap by growing toward it or by 

 sending out a process. However, in one set of observations in 

 which the brown injected mass, with its sprinkling of refractile 

 droplets and its circle of pigmented leucocytes, had shifted its 

 position so that it came to occupy a position very near to a 

 blood-vessel, leucocytes, containing pigment and droplets were 

 seen, on three successive days, crawling around the wall of the 

 blood capillary. Although they were watched continuously for 

 several hours, they were not seen to lose their pigment. This 

 was the only instance, in all the experiments, in which there 

 was a suggestion that the neighboring blood capillaries might 

 play a part in the absorption of the injected fat. 



The absorption of the oleic acid, or sodium oleate, proceeded 

 more quickly than in the case of the olive oil but was not com- 

 plete after ten days. This substance changed its shape and 

 shifted its position much more noticeably than the olive oil. 



3 and 4- Cream and yolk of egg. Since these two substances 

 jvere similar in appearance, upon injection, and produced iden- 

 tical results, a single description will suffice for them both, A 

 very small amount of each substance was injected into the sub- 

 cutaneous tissue of the tail. Under the binocular microscope, 

 the injection appeared as a line of black dots; viewed under the 

 compound microscope, both the cream and yolk were seen to 

 consist mainly of an emulsion of very small fat droplets. 



Soon after the injection, many leucocytes could be seen crawl- 

 ing through the walls of neighboring blood capillaries and moiing 

 toward the yolk or cream. Upon reaching the injected substance, 

 these cells proceeded to ingest the fat droplets. Soon after 

 taking up the drops of cream or yolk, the leucocytes became pig- 

 mented, owing to the nmnbers of very small granules which they 



