190 PHAGOCYTOSIS 



toxin, attracts the leukocytes. The bacilli and spores exert a positive 

 chemotaxic effect upon leukocytes. In like manner the presence of 

 certain non-pathogenic bacteria occupies the activity of the phago- 

 cytes, giving time for the tetanus bacillus to elaborate its toxin. When 

 this point is reached, the bacilli are protected by their own secretion. 

 Likewise, if a culture containing the spores of symptomatic anthrax 

 be heated high enough (80 to 85 C.) to destroy any toxin that may be 

 present, and be injected into an animal, the phagocytes rush to the 

 point of inoculation and devour the spores. If, however, the spores, 

 free from toxin, be rubbed up thoroughly with fine sterilized sand and 

 particles of this mixture be introduced under the skin, the sand pro- 

 tects the spores long enough for them to develop toxin, infection 

 results, and the animal dies. A similar experiment has been made 

 with the spores of malignant edema. If toxin-free spores be mixed 

 with agar and bits of this be placed under the skin, the phagocytes 

 attack the agar, but while they are at work on this the enclosed spores 

 develop, produce toxin and infect the animal. If the bits of agar after 

 being placed under the skin are crushed between the fingers, the 

 phagocytes reach the spores, devour them and the animal is protected. 

 Certain non-pathogenic bacteria, which are frequently present in the 

 soil, protect the spores of malignant edema. 



In natural immunity to tuberculosis, phagocytes develop into giant 

 cells, destroy the bacilli and lead to calcification. When the spirilla 

 of relapsing fever are injected into the peritoneal cavity of a guinea- 

 pig, they are devoured by phagocytes. In animals naturally immune 

 to certain cocci gonococcus, pneumococcus, streptococcus and staphy- 

 lococcus phagocytosis is in evidence. Natural immunity to pathoy 

 genie organisms other than bacteria, such yeasts, moulds, trypano- 

 somes and protozoa, is apparently largely due to phagocytic activity. 



As has been stated, Metchnikoff holds that the polynuclear leuko- 

 cytes, which he calls microphages, play the important role in the bac- 

 terial diseases. The eosinophils also are capable of taking in and 

 digesting bacteria. This teaching is so fully accepted that a marked 

 increase in polynuclear leukocytes is taken as an indication of bacterial 

 infection. Microphages are transported from one part of the body 

 to another in blood and lymph, and by means of their pseudopodia, 

 they have independent movements. Under the microscope they can be 



