278 



INFECTION AND RESISTANCE 



EAT LEPROSY BACILLI GROUPED IN THE EEMAINS OF 

 DEAD SPLEEN CELLS GROWING IN PLASMA. 



cytosis is therefore 

 an attribute of a 

 considerable num- 

 ber of different va- 

 rieties of cells. In 

 the circulating 

 blood the polynu- 

 clear leukocytes are 

 the most actively 

 motile and phago- 

 cytic elements. The 

 eosinophile cells 

 may also take up 

 foreign particles 

 and bacteria, as 

 may also the large 

 lymphocytes. The 



Drawn after illustration in Zinsser and Carey, Journal small lymphocytes 

 of the A. M. A., Vol. 58, 1912. and mast cells are 



either entirely inac- 

 tive in this respect, or, at least, possess phagocytic powers under ex- 

 ceptional circumstances only. This does not mean, however, that 



these last-named cells may 



not accumulate at the point 



of invasion nor that they 



may not play an important 



part in the defence of the 



body. It is well-known, of 



course, that, in tuberculosis 



and a number of other con- 

 ditions, the lymphocytes 



may form the majority of 



the cellular elements which 



accumulate at the site of 



the lesion. Among the 



fixed cells of the body it is 



probable that phagocytosis 



may be carried on by cells 



<of many different origins, 



though the identification of 



PHAGOCYTOSIS or SENSITIZED PIGEON COR- 

 PUSCLES BY ALVEOLAR CELLS OF LUNG. 



Drawing made after photomicrograph pub- 

 lished by Briscoe, Journal of Path, and 

 Bact., Vol. 12, 1908. 



cells in tissues is often a 

 purely morphological prob- 

 lem, and therefore fraught 

 with many possibilities of 

 error. Probably the most active fixed tissue cells are the endothelial 

 cells of the blood vessels and those which line the serous cavities, the 



