PHAGOCYTOSIS 285 



though inoculation into guinea pigs is nevertheless successful, pro- 

 ducing typical tuberculosis. Much 22 has studied this peculiar state 

 of affairs particularly and has shown that, although such lesions may 

 show no tubercle bacilli by the Ziehl-Neelsen carbol-fuchsin method, 

 .staining by a modified Gram technique will reveal numerous Gram- 

 positive rods and granules which have lost their acid-fast properties. 

 This, too, if true, and the evidence is very much in its favor, would 

 point to an ability of the macrophages to digest the waxy substance 

 -of the tubercle and other acid-fast bacilli, a property not possessed 

 by- the microphages. It may, of course, mean on the other hand that 

 the tubercle bacilli in the lesion have not developed the waxy condi- 

 tion. 



ClIEMOTAXIS AND LEUKOCYTOSIS 



The part played by the phagocytic cell in the defence of the body 

 against the entrance of bacteria and other foreign substances consists, 

 then, of two functionally different phases. The first is an active 

 motion of the cells toward the point attacked, and their accumulation 

 .about the noxious agent, the second consists in the act of ingestion 

 itself. 



The motion of the leukocytes toward the invading substances 

 indicates a sensibility on the part of the cell to changes in its environ- 

 ment incited by the foreign agent, and since the stimuli most likely 

 to reach the leukocytes and bring about this alteration in the direc- 

 tion of their movements are chemical in nature, the phenomenon is 

 spoken of as "chemotaxis." This term was borrowed from Pfeffer, 23 

 who studied similar phenomena in connection with many freely 

 motile plant cells, spermatozoa, and bacteria. Since the change of 

 direction brought about in a moving cell by such influences may be 

 such as either to attract or to repel, the term "positive chemotaxis" 

 is used to designate the former and that of "negative chemotaxis" 

 the latter. 



The property of chemotaxis is of vital interest in the present 

 connection, since, whatever may be our opinion regarding the relative 

 Talues of phagocytosis and serum protection in immunity, the great 

 importance of the phagocytic process cannot be questioned, and any 

 agency which repels the approach of the phagocytes must be a detri- 

 ment, while any factor which attracts them is, of necessity, a power- 

 ful means of defence. In the investigations upon the nature of infec- 

 tious diseases attention has been concentrated upon the phenomenon 

 of phagocytosis, and the relations governing the act of ingestion 

 have been very thoroughly studied. The details of the chemotactic 

 phenomenon, however, though of equal importance, are much more 



22 Much. "Beitrage zur Klinik der Tuberk.," Vol. 8, 1907, Hft. 1 and 4. 



23 Pfeffer. "Untersuch. a. d. Botan. Inst. Tubingen," Vols. 1 and 2, 1884 

 rand 1888. 



