216 INFLAMMATION 



This " amibodiastase, " 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 highly 

 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 secure either invertase or lipase in extracts of 

 protozoa. Whether bacteria are digested in leucocytes by the 

 same enzymes that digest the leucocytes themselves after they 

 are killed (i. e., the autolytic ferments), or by some specialized 

 enzyme, is not known. Metchnikoif, however, has noted the 

 localized production of acid in the cytoplasm of leucocytes of 

 the larva of Triton toeniatus. The eventual excretion of the 

 remains of the bacteria or other foreign bodies by the phagocytes 

 is ascribed by Rhumbler to changes in the composition in the par- 

 ticles through digestion, so that they have a greater surface affinity 

 for the surrounding fluids than for the protoplasm of the cell. 



Phagocytosis cannot be readily ascribed to chemotaxis, how- 

 ever, in the case of phagocytosis of perfectly insoluble, chemic- 

 ally inert particles, such as coal-dust. The leucocytes seem to 

 take up foreign bodies without reference to their nutritive value, 

 absorbing India-ink granules and bacteria impartially when they 

 are injected together, and loading themselves so full of carmine 

 granules that they cannot take up bacteria subsequently injected. 

 It is possible that foreign bodies first become coated with a 

 layer of altered proteid which then leads to phagocytosis, but 

 there is no sufficient evidence for this surmise. 



Not only leucocytes but tissue cells are capable of moving 

 and performing phagocytosis when properly stimulated, and 

 apparently all or nearly all fixed cells may act as phagocytes 

 under some conditions. Their power of independent movement 

 is much less than their phagocytic power. Endothelial cells 

 are particularly active in phagocytosis, as also are the new meso- 

 dermal cells produced in inflammation. Apparently they obey 

 the same laws as the leucocytes, and not only take up bacteria, 

 but also fragments of cells and tissues, red corpuscles, and even 

 intact leucocytes and other cells. Brodie 1 considers that phago- 

 cytosis by endothelial cells in lymph-glands is the natural end of 

 the leucocytes, and red corpuscles seem to have a similar fate. 



Phagocytosis is usually accomplished solely by the cytoplasm 

 of the cells, the nuclei maintaining a passive role ; but, according 

 to Detre and Selli, 2 the phagocytosis of particles of lecithin 



1 Jour, of Anat. and Physiol., 1901 (35), 142. 



2 Berl. klin. Woch., 1905 (42), 940. 



