438 ELIOT R. CLARK AND ELEANOR LINTON CLARK 



THE REACTION OF LEUCOCYTES 



The behavior of the leucocytes was essentially the same toward 

 each of the various substances employed. Figure 1 illustrates 

 the initial response of leucocytes toward the injected material. 

 These cells migrate from nearby blood-vessels and move toward 

 the injected fat and within five or ten minutes after reaching it, 

 they are seen to contain refractile droplets and brown granules. 

 In the case of the single relatively large globules of olive oil, 

 the leucocytes formed a ring around the oil consisting of a single 

 layer of cells. In the case of the soap of oleic acid, the leuco- 

 cytes penetrated the substance for some distance and remained 

 as several layers in the less compact peripheral portion of the 

 mass. In the case of the yolk of egg and cream, leucocytes 

 wandered toward the injection site and actively engulfed the 

 small fat droplets composing the respective emulsions. 



In all of the substances used for the experiments, leucocytes 

 containing refractile droplets and brown granules, were ob- 

 served to wander away from the site of injection and to move 

 toward a nearby lymphatic capillary. After coming into close 

 contact with the wall or tip of the lymphatic, they remained 

 there for varying lengths of time (five to ten minutes in the 

 case of the yolk and cream, about twenty minutes in the ease 

 of the oleic acid, and as long as ten or twelve hours when they 

 contained drops of olive oil). This relationship of leucocyte to 

 lymphatic is shown in figures 6, 7 and 8. At first sight, it often 

 seemed that such a leucocyte was just upon the point of entering 

 the lymphatic. However, when the region was observed closely 

 over a sufficient period of time, the leucocyte was always seen 

 to wander away. In fact, no pigmented leucocytes were seen to 

 enter a lymphatic 'during the course of any of the observations. 

 At the time of wandering away, the pigment within these phago- 

 cytic cells either disappeared entirely or diminished perceptibly 

 in amount (figs. 7 and 8). 



From these observations alone it was of course impossible to 

 determine the exact chemical process by which the various fatty 

 substances were absorbed. As an interpretation of these records 



