EXPERIMENTAL DEMONSTRATION OP PHAGOCYTOSIS 57 



this kind, washed red blood corpuscles. Now, if a few cubic centimeters 

 of these washed corpuscles suspended in physiologic salt solution are 

 injected into the peritoneal cavity of a guinea-pig and after a short 

 time, say one hour, removed from the peritoneum together with an 

 exudate from the abdominal cavity which has been mixed with 

 them the following is found: The exudate contains numerous large 

 mononuclear white blood corpuscles of the guinea-pig, and these 

 cells contain many red bood corpuscles of the goose. If some of the 

 peritoneal exudate is removed afterward at intervals of thirty minutes, 

 the goose corpuscles will be found more and more digested in the 

 large mononuclear cells of the guinea-pig, demonstrating that certain 

 cells of mammalian animals possess phagocytic properties. 



In 1883 Metchnikoff first claimed that phagocytosis protects the 

 higher animals against infection by disease-producing pathogenic 

 bacteria. His opponents, however, showed that in animals dead from 

 anthrax, numerous anthrax bacilli were seen in the blood, none of 

 which were being taken up or digested by phagocytic cells. Metch- 

 nikoff then succeeded in demonstrating that in animals not sus- 

 ceptible to anthrax such phagocytosis of bacilli takes place and 

 that the lack of susceptibility depends upon the fact that the 

 anthrax bacilli are taken up and destroyed by phagocytes. 



Phagocytic Cells (Macrophages and Microphages). It may very prop- 

 erly be asked, What kind of cells of the higher animals possess the 

 power of phagocytosis ? With a single exception all cells which have 

 the power to act as phagocytes are derived from the middle germinal 

 layer, the mesoderm or mesoblast. Among these cells two classes 

 are represented, namely, wandering cells or leukocytes and fixed con- 

 nective-tissue cells. Not every white blood corpuscle or leukocyte can 

 act as a phagocyte. As a rule, only some of the polynuclears and the 

 large mononuclears are phagocytic. Among the fixed tissue cells 

 endowed with the power of phagocytosis are the large mononuclear 

 cells of the spleen, the lymph sinuses and the lymphatic endothelia of 

 the lymph clefts, the bone corpuscles, the myeloplaxes of the bone 

 marrow, and other giant cells. Metchnikoff divides all the phagocytic 

 cells into macrophages and microphages (large and small phagocytes). 

 The former destroy particularly dead or foreign cells (foreign blood 

 corpuscles) while the latter generally destroy bacteria. (The largest 

 kind of macrophages, the multinuclear giant cells, also destroy bac- 

 teria.) In general it can be stated that the wandering cells, the 

 leukocytes, are more important in phagocytosis than the fixed cells. 



Experimental Demonstration of Phagocytosis. Phagocytosis of patho- 

 genic bacteria can be easily demonstrated by numerous experiments. 

 If a small amount of a twenty-four-hours-old culture of virulent 

 anthrax bacilli is injected into the lymph sac of a frog, and if from 

 time to time some of the injected fluid is removed by the aid of a 

 small pointed glass pipette, it will be found that the white corpuscles 

 of the frog take up and digest more and more anthrax bacilli until 



