262 INFLAMMATWX, RFJJESERATlOy . GROWTH 



The influence of light, mechanical stimulation, and gravity upon 

 leucocytes seems not to have been studied. The phagocytosis of insol- 

 uble 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 s- 



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 ha.s 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 undoubtedly 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, Faraiiioeciuui, and some other 

 varieties) to contain a strongly acid fluid. JNIiss Greenw^ood ^* has also 

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

 stimulation of injected particles, whether nutritious or not. ]Mouton ^® 

 has been able to extract from the bodies of protozoa (rhizopods) a 

 feebl}^ proteolytic enzyme. This " amihodiastase," as he calls it, is 

 active in alkaline, and faintly acid media, and digests colon bacilli that 

 have been killed by heat, but not living bacilli. This last fact is 

 bighly suggestive in connection with the important question of whether 

 leucocytes engulf and destroy virulent bacteria or only those that have 

 been previously injured by the tissue fluid. It was impossible to se- 

 cure either invertase or lipase in extracts of protozoa. Whether bac- 

 teria are digested in leucocytes by the same enzymes that digest the 

 leucocytes themselves after they are killed {i. e., the autolytic fer- 

 ments), or by some specialized enzyme, is not known. ]\Ietclinikotf, 

 however, has noted the localized production of acid in the cytoplasm 

 of leucocytes of the larva of Triton taeni-atits. The eventual excre- 

 tion of the remains of the bacteria or other foreign bodies by tlie 



35 Sco review by MotsclinikofT, Kollo and Wassorniaiin's llaiulh. d. Patli. ^^ik- 

 roorf^anisnien, 1!)1.3 (IT), t;").") ; also II. J. TTainl)iirm'r. ""PIin sikaliscli-clu'inische 

 Unt('rsucluinf,'-on iiber Pliapocyten," Bergmann. Wioshadon, 1012. wliere is given 

 a fiill account of the author's important researches on the ])riiu'iples of phagocytic 

 behavior. 



30 See Opie, Jour. Exp. IMed., lOOf) f8). 410. 



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



38 Jour, of Physiol.. 1804 (16). 441. 



30 C. R. Acad.'des Sciences, 1901 (13.3), 244. 



