THEORIES OF CIIEMOTAXIS AND PHAGOCYTOSIS 259 



Leucocytes contain substances which are stronfj;ly bactericidal, in- 

 dependent of the action of the blood serum, and which have been 

 called endolysins;^'' they are resistant to 65° or even higher, and seem 

 to be bound rather firmly to the protoplasm of the leucocytes, for they 

 resist extraction except by vigorous methods; they have a complex 

 structure like the amboceptor-complement bacteriolysins of the serum, 

 and are not specific (Weil).^^ They do not pass through porcelain 

 filters readil}^ are precipitated by saturation with ammonium sul- 

 phate, and resemble the enzymes in many respects."^ It is probable 

 that the endolysins act upon bacteria that have been phagocyted, and 

 perhaps also upon free bacteria when liberated in suppuration through 

 disintegration of the leucocytes. Lymphocytes and macrophages seem 

 to be devoid of this endolysin.'^" 



Phagocytosis of hving virulent bacteria may not always be an un- 

 mixed benefit. Besides the obvious possibility of transporting the 

 bacteria and spreading infection, we have also evidence that living 

 bacteria may be protected through phagocytosis, against the action of 

 bactericidal substances in the blood and tissues (Rous and Jones). '^^ 



THEORIES OF CHEMOTAXIS AND PHAGOCYTOSIS 



On the assumption that leucocytes obej- the same laws in their mo- 

 tions as do the amebse, studies of the latter and of other forms of 

 protozoa have furnished most of the ideas, hypotheses, and theories 

 of the forces involved in leucocytic activities. The structural rela- 

 tion 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 pseudopodia and protoplasmic streaming, 

 taking other smaller bodies into its substance and digesting them, 

 reacting similarly to like stimuh, and containing similarly a nucleus 

 and many granules. The differentiation of the protoplasm of the 

 ameba into a clear outer ectosarc and an inner granular endosarc is 

 perhaps an important difference, but as far as the two forms of cells 

 have been studied, the effect of this difference in structure does not 

 seem to have been considered. That the unicellular protozoa, devoid of 

 any central nervous system, and without any apparent co-ordinating 

 mechanism, seem able to move about in a purposeful way, going toward 

 food supplies and away from injurious agencies, toward or away from 

 hght, heat, and chemicals, has long attracted the interest of physi- 

 ologists, particularly as in these single-celled organisms we may look 

 for the simplest conditions of existence and the most elementary hfe 

 processes. It seems absurd to imagine that a paramoeciiwi goes toward 



" For general review see lOing, Zeit. Iramunitat., 1910 (7). 1. 



«8Arch. ft Hvg., 1911 (74), 289. 



" Manwaring, Jour. Exp. Med., 1912 (16), 250. 



" See Schneider, Arch. f. Hvg., 1909 (70), 40. 



^1 Jour. Exper. Med., 1916 (23), 601. 



