PHAGOCYTOSIS 277 



hours after the injection. After this, there is a gradual diminution in 

 the leucocytic elements until the fluid in the peritoneal cavity again 

 reaches its normal condition. It is plain, therefore, that the presence 

 of the foreign material in the peritoneal cavity has, after a primary 

 repellent action upon the phagocytes, attracted them in large numbers 

 to the site of the foreign substance. Such repelling or attracting in- 

 fluences upon the leucocytes are spoken of as negative or positive 

 chemotaxis. The reasons for chemotaxis are not well understood. In 

 the case of bacteria, which chiefly interest us in the present connection, 

 chemotactic attraction or repulsion is intimately dependent upon the 

 nature of the microorganism, and very probably has a definite relation- 

 ship to its virulence. Whether or not the principles of chemotaxis may 

 serve to explain the hypo- and hyper-leucocytoses, observed and diag- 

 nostically utilized in clinical medicine, is by no means positive. It is 

 Hkely, however, that the two phenomena are closely associated. Leva- 

 diti ' beUeved that he obtained some evidence that negative chemotaxis 

 may take place within the blood-vessels when he noticed that the intra- 

 venous injection of cholera spirilla into immunized guinea-pigs resulted 

 in an immediate disappearance of leucocytes from the circulating blood, 

 and their accumulation in the internal organs. On the other hand, this 

 may possibly be more logically explained by a concentration of both 

 bacteria and leucocytes in the capillary system of such an organ as the 

 liver, as it is known that injected bacteria rapidly disappear from the 

 general circulation, but may be demonstrated in the various organs for 

 some time after injection. 



We have seen, therefore, that the invasion of the animal body by 

 foreign material, living or dead, is followed by a prompt response on the 

 part of the phagocytic cells. In the case of bacteria, when these are 

 deposited in the subcutaneous areolar tissues, the inflammatory reaction 

 which follows brings with it an emigration of microphages (polynuclear 

 leucocytes) from the. blood-vessels — and these are the so-called pus 

 cells. When the injection of bacteria is intraperitoneal, after a primary 

 diminution, there is an increase of leucocytes in the peritoneal cavity 

 which soon results in the formation of a copious turbid exudate. If the 

 pus of an abscess or the exudate from an infected peritoneum is ex- 

 amined microscopically, it will be seen that many of the microphages 

 have taken bacteria into their cytoplasm. That fully virulent living 

 bacteria can be so taken up has been variously proven. The phago- 



^Levaditi, Presse m^d., 1900. 



