332 INFECTION AND IMMUNITY 



variety, the maximum of the reaction being reached about eighteen to 

 twenty-four 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 influences upon the leucocytes are spoken of as negative or 

 positive chemotaxis. The reasons for chemotaxis are not well under- 

 stood. 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 relationship to its virulence. Whether or not the principles 

 of chemotaxis may serve to explain the hypo- and hyper-leucocytoses, 

 observed and diagnostically utilized in clinical medicine, is by no 

 means positive. It is likely, however, that the two phenomena are 

 closely associated. Levaditi 4 believed that he obtained some evidence 

 that negative chemotaxis may take place within the blood-vessels when 

 he noticed that the intravenous 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 examined microscopically, it will be seen that 

 many of the microphages have taken bacteria into their cytoplasm. 



4 Levaditi, Presse med., 1900. 



