PHAGOCYTOSIS 197 



A guinea-pig receives an intraperitoneal injection of goose's blood. Immediately 

 following this, the leucocytes disappear from the peritoneal fluid. This is due partly 

 to a destruction of leucocytes (Phagolysis) and partly because the leucocytes are re- 

 pulsed and settle upon the peritoneal wall. In one to two hours this so-called negative 

 phase is overcome and there is an increase of the leucocytes, especially of the macro- 

 phages in the exudate (Hyperleucocytosis). Now, the leucocytes can be seen sending 

 forth short protoplasmic processes pseudopodia, by means of which the erythrocytes 

 are drawn into tHe phagocytes. After a short time the macrophages are filled with the 

 erythrocytes. At first the ingested cells appear normal; gradually, however, they un- 

 dergo changes, which are clearly visible in the unstained specimen, indicative of a 

 disintegrating process, within the body of the phagocytes. 



."'" .-; 



The same phenomenon as described for goose's erythrocytes can also be 

 observed with bacterial bodies. 



In order to exclude the possible bactericidal influences of the serum, it is advisable 

 when one is working with bacteria which are readily destroyed, as cholera vibrios, to 

 previously induce a hyperleucocytosis in the peritoneal cavity. The guinea-pig receives 

 an intraperitoneal injection of 10 to 20 c.cm. of sterile bouillon or aleuronat solution; 

 in about twelve hours hyperleucocytosis takes place, and a capillary pipette inserted 

 into the peritoneal cavity will withdraw a thick and turbid exudate of leucocytes. 



If this animal is injected intraperitoneally with bacteria, and a smear of 

 the peritoneal fluid made a short time after the inoculation, the bacteria 

 will be seen lying within the microphages. This important fact has been 

 variously interpreted. Pfeiffer and his pupils claim that the bacteria are 

 first destroyed or their virulence greatly diminished by the bactericidal 

 power of the serum and exudate, and that the phagocytes act only as 

 receptacles for these already destroyed bacteria. Metchnikoff believes 

 that the phagocytes take up the living bacteria and destroy them, thus 

 representing these cells as the most important weapons of the organ- 

 ism in its protection against infection. 



" Whenever an organism, that has lost its susceptibility to a par- 

 ticular infection, either on account of a natural born immunity or one 

 artificially attained, comes into conflict with the etiological agent, a 

 struggle arises between the latter and the phagocytes of the threatened 

 individual. The phagocytes appear as victors, since they take up the 

 bacteria into their protoplasmic bodies and digest them, thus forever 

 destroying the evil." (Metchnikoff cited by Levaditi.) 



Critically considered, there can be no doubt that the phagocytes by their 

 very nature are capable of dealin gwith living virulent bacteria. At the 

 same time one must observe that the opsonins and bacteriotropins of the 

 serum, soon to be discussed, in most instances previously modify the living 

 bacteria in a way at present still unknown. That, however, the phagocytes 

 can ingest bacteria or protozoa which are alive and active, has been demon- 

 strated by Metchnikoff 's school. Phagocytosis experiments were under- 



