62 THE DEFENSIVE FORCES OF THE MACROORGANISM 



infection. In the laboratory the same can be shown by introducing 

 tiny capillary tubes filled with bacterial cultures (staphylococcus, 

 typhoid bacillus, anthrax bacillus, etc.) into the peritoneal cavity 

 of frogs and leaving them for twenty-four hours. At the expiration 

 of this time the tubes are removed and examined under the micro- 

 scope, when it will be seen that the ends of the tubes especially are 

 filled with leukocytes, the majority of which contain bacteria. Every 

 worker in the clinical laboratory also is no doubt familiar with the 

 precision with which neutrophilic leukocytes will enter the field of 

 vision and sooner or later proceed to devour an extracellular malarial 

 organism which has been left in situ. 



Chemotaxis. This property on the part of the polynuclear neutro- 

 philic leukocytes to migrate to a given point at which bacteria or 

 other organisms have entered the body is generally referred to chemo- 

 tactic influences which the latter exert upon the leukocytes, the term 

 chemotaxis being used to designate a certain sensibility on the part 

 of living protoplasm in general to various chemical bodies; it is a 

 characteristic, no doubt which the leukocyte has inherited from its 

 protozoan ancestors. 



According to the type of chemotaxis, i. e., the existence of attract- 

 ing or repelling influences which chemical substances exercise upon 

 living cells we speak of positive and negative chemotaxis. That the 

 latter also may occur in bacterial infections is an established fact 

 and it is noteworthy that a negative effect may be caused by a viru- 

 lent strain of the same organism which in a non-virulent condition 

 would produce positive chemotaxis. The important bearing which 

 the type of chemotaxis must have upon the production of an infec- 

 tion is, of course, self-evident. If in a given case, in which the main 

 defense lies in phagocytosis, phagocytosis cannot occur in conse- 

 quence of negatively chemotactic influences, it is clear that a 

 generalized infection must be the outcome. 



Of the nature of the substances which determine the chemotactic 

 effect we know relatively little. Living bacterial cells are mani- 

 festly not necessary to this end, for we obtain the same collections 

 of leukocytes in the peritoneal cavity of frogs (see above) with dead 

 organisms and even with the soluble products of bacterial bodies, as 

 with the living organisms themselves, and it has long been known 

 that the injection of sterilized cultures of various organisms will 

 lead to the formation of sterile abscesses (Friedlander's bacillus, 



