246 VARIETIES OF PHAGOCYTES 



lymphocyte may then present a remarkable appearance, having 

 ingested two or even three red corpuscles, each as large as itself, 

 the narrow band of protoplasm being extended over the corpuscle 

 in a most extraordinary way. 



It is noticeable, too, that even among the polynuclears there are 

 great differences in phagocytic powers. This is best seen in a film 

 of pus from a case of gonorrhoea, in which certain cells (indis- 

 tinguishable from the others) are packed full of cocci, whereas the 

 vast majority are entirely free. The same fact is brought out 



FIG. 49. RED CORPUSCLES INGESTED BY POLYNUCLEAR LEUCOCYTES 

 AND LYMPHOCYTES. (Original.) 



clearly in opsonic experiments, where some leucocytes are often 

 found to take up very large numbers of bacteria, the general 

 average of the other cells being low. 



Besides the leucocytes, some of the tissue cells, which are 

 either free or have the power of becoming so, are active phago- 

 cytes. Of these, the most important are the endothelial cells. 

 These are only flat plates of protoplasm when under normal 

 conditions. When submitted to the action of almost any irritant 

 they become cuboidal or columnar, and are then most active 

 phagocytes. A good example of this may sometimes be seen in 

 sections of a thrombosed vein at a certain stage : the endothelial 

 cells are columnar and contain much protoplasm, and this latter 

 is packed with pigment granules absorbed from the altered blood 

 in the lumen. But the process goes farther than this, and the 

 endothelial cell (whether of the serous membranes, vessels, or 

 lymph clefts) either breaks loose from its attachments or buds off 



