PHAGOCYTOSIS 205 



If mixtures of leucocytes and bacteria sensitized with oj)Sonins are kept at low- 

 temperature, the bacteria become attached to the surface of the leucocytes, not 

 being ingested until the mixture is wanned.^' This indicates that two separate 

 processes are involved in phagocytosis. 



Temperature probably plays but a minor part in attracting leucocytes in 

 pathological processes, however. The local heat of an inflamed area is due chiefly 

 to the accumulation of blood in the part, and would not influence the leucocytes 

 to migrate from the still warmer blood into the ti.ssues. Segale,^* hciwever, has 

 demonstrated tiiat there is some actual heat production through increased metab- 

 olism in inflamed tissues, which may have .some slight effect. By increasing 

 motility the temperature of fever may favor migration and phagocytosis, and 

 local application of heat to inflamed areas may induce local leucocytic accumula- 

 tion. In burns the duration of the period of excessive temperature is usually 

 too brief to account for the attraction of leucocytes that results; this accumu- 

 lation is undoubtedly due to the products of the resulting cell degenerations. 



The influence of light, mechanical stimulation, and gravity upon 

 leucocytes seems not to have been studied. The phagocytosis of 

 insoluble non-nutritive particles has been ascribed to tactile stimulation, 

 but the details of the operation of such stimuli are unknown, and the 

 entire question of tactile stimulation is unsettled. In experiments 

 with elder pith it has been observed that leucocytes penetrate to the 

 center, even when the pith contains only physiological salt solution. 

 As Adler remarks, it is difficult to explain such migration as due to 

 tactile stimuli; but on the other hand, no other explanation has been 

 offered. 



Phagocytosis *= 



The engulfing of bacteria, cells, tissue products, etc., by leucocytes 

 seems to be but an extension of the phenomenon of chemotaxis. When 

 the substance toward which the leucocyte is drawn is small enough, 

 the leucocyte simply continues its motion until it has flowed entirely 

 about the particle. Later the particle becomes, as a rule, more or less 

 altered within the cell, unless it is a perfectly insoluble substance, such 

 as a bit of coal-dust. This action upon the engulfed object is un- 

 doubtedly due to the action of intracellular enzymes. ^*^ Protozoa 

 take their food into a specialized digesting vacuole which has been 

 shown by Le Dantec*^ (in Stentor, Paramoecium, and some other varie- 

 ties) to contain a strongly acid fluid. Miss Greenwood*^ has also 

 demonstrated acid in several forms of protozoa, which is formed under 

 stimulation of injected particles, whether nutritious or not. Mouton'*^ 



^^Ledingham, Proc. Royal Soc, 1908 '80), 188; Sawtchenko, Arch. sci. biol. 

 1910 (15), 145. 



" Jour. Exp. Med., 1919 (29), 235. 



** See review by Metschnikoff, Kolle and Wassermann's Handb. d. Path. Mik- 

 roorganismen, 1913 (II), 655; also H. J. Hamburger. " Physikalisch-chemische 

 Untersuchungen iiber Phagocyten," Bergmann, Wiesbaden, 1912, where is given 

 a full account of the author's important researches on the principles of phagocytic 

 behavior. 



« See Opie, Jour. Exp. Med., 1906 (8), 410. 



" Ann. d. I'Inst. Pasteur, 1890 (4), 776. 



" Jour, of Physiol., 1894 (16), 441. 



" C. R. Acad, des Sciences, 1901 (133), 244. 



