218 INFLAMMATION 



Results of Phagocytosis. After phagocytosis has been 

 accomplished, the fate of the engulfed object depends upon its 

 nature. If digestible by the intracellular enzymes it is soon 

 destroyed, but in the case of engulfed living cells, it seems 

 probable that they must be first killed they form no exception 

 to the rule that living protoplasm cannot be digested. This 

 brings forward the question of so much importance in the 

 problems of immunity : Do living bacteria enter phagocytes, 

 or are they first killed by extracellular agencies before they can 

 be taken up ? At the present time it seems to be positively 

 established that leucocytes do take up bacteria which are still 

 viable, and which may either grow inside the leucocyte or may 

 be destroyed by intracellular processes. 1 On the other hand, 

 leucocytes do not take up extremely virulent bacteria, and hence 

 the question as to the relative importance played by the leuco- 

 cyte and by the body fluids is still undetermined. It is prob- 

 able that phagocytosis by fixed tissue-cells is of much less 

 importance in checking bacterial growth than is phagocytosis 

 by leucocytes. Thus Ruediger's experiments showed that emul- 

 sions of organs, with the exception of bone-marrow, do not 

 destroy streptococci which are readily destroyed by leucocytes. 



Indigestible substances may remain in cells, particularly in 

 fixed tissue cells, for very long periods, if the substances are 

 chemically inert. The leucocytes seem to transfer the indiges- 

 tible particles which they have engulfed to other tissues, 

 particularly to the lymph-glands ; this is probably accomplished 

 by phagocytosis of the ladened leucocytes by the macrophages 

 of the lymph sinuses, but how the insoluble particles are later 

 transferred to the gland stroma or perilymphangial tissues, 

 where they are chiefly found in such conditions as anthracosis, 

 etc., is quite unknown. 



THEORIES OF CHEMOTAXIS AND PHAGOCYTOSIS 

 On the assumption that leucocytes obey the same laws in 

 their motions as do the amebse, studies of the latter and of 

 other forms of protozoa have furnished most of the ideas, hypo- 

 theses, and theories of the forces involved in leticocytic activities. 

 The structural relation of the leucocyte to the ameba is striking, 

 although, by no means complete ; the relation of their activities 

 is even closer. Each is a microscopic, independent, unicellular 

 organism, moving freely in all directions by means of pseudo- 

 podia and protoplasmic streaming, taking other smaller bodies 

 into its substance and digesting them, reacting similarly to like 

 1 See Kuediger, Jour. Amer. Med. Assoc., 1905 (44), 198. 



