280 INFECTION AND RESISTANCE 



or leprosy bacilli which are injected into an animal may be at first 

 taken up by polynuclear leucocytes or microphages, by which they may 

 even be carried into the lymph channels and distributed, perhaps to 

 the detriment of the host. But these cells, probably because they lack 

 a lipolytic ferment by means of which the waxes of the acid-fast or- 

 ganisms can be digested, cannot destroy the bacteria, which are then 

 attacked by other cellular elements at the site of their final deposit. 



That fixed tissue cells as a matter of fact play a very important 

 role in the disposal of invading bacteria is becoming more and more 

 clear. Kyes 18 showed a few years ago that the immunity of the 

 pigeon to pneumococcus infection is largely due to active removal of 

 the bacteria by the Kupfer cells in the liver. Bull's 10 observations 

 on the intravascular agglutination of typhoid bacilli which are then 

 phagocyted by cells in the liver and spleen point in the same direc- 

 tion, and recently Hopkins and Parker 19a in our laboratory have 

 shown that streptococci injected into rabbits and cats are rapidly re- 

 moved from the circulation, the removal being to a great extent due 

 to phagocytosis carried on by the endothelial cells in the lungs and 

 by similar cells in the liver and spleen. 



In many such cases the further resolution of the foreign sub- 

 stance is accomplished by an important type of phagocytosis which is 

 characterized by the formation of the so-called giant cells. These 

 cells are of varying appearance in different conditions and locations. 

 Thus the giant cells which form about foreign bodies, such as the 

 small cotton fibers occasionally left in wounds, or injected particles of 

 paraffin or iron splinters, etc., are quite characteristic and distinct 

 from the giant cells of tuberculous foci, or of rhinoscleroma, glanders, 

 or leprosy. They are all large cells, containing often numerous 

 nuclei which form either by the fusion of several cells, as claimed by 

 Borrell, 19b Hektoen, 19c and others, or by the cleavage of the nuclei 

 alone, without coincident divisions of the cytoplasm. 



Although it is, of course, impossible to decide definitely upon 

 purely morphological grounds, the researches of Hektoen especially 

 would lead one strongly to favor the former view. It is equally 

 difficult to decide the origin of giant cells, and endothelial, connec- 

 tive tissue, and even leucocytic origin has been claimed for them. 

 Yet in no case has it thus far been possible to actually observe their 

 formation by a method which could positively decide this point. 



In order to gain a clear conception of the participation of phago- 

 cytes in the response of the body to injury or invasion, it will be 

 useful to follow out the process of inflammation as it occurs in the 



18 Kyes. Journal of Infectious Diseases, Vol. 18, 1916, p. 272. 



19 Bull. Journal of Exp. Med., Vol. XX, p. 237. 

 19a Hopkins and Parker. Paper in Manuscript. 

 i9b Borrell. Ann. de I'Inst. Past., 7, 1893. 



19c Hektoen. Jour. Exp. Med., 3, 1898, p. 21. 



