10 STUDIES IN IMMUNITY. 



frequently determined by individual researches, so frequently 

 demonstrated in articles dealing with the general problem of 

 immunity, that it would scarcely be necessary to repeat the history 

 of its development and to enumerate the data on which it has been 

 founded. We may be permitted, however, to recall the most 

 demonstrative facts which may be cited in confirmation of this 

 doctrine. 



The phagocytic function belongs essentially to the polynuclear 

 amphophiles,* to the large mononuclear leucocytes and to certain 

 endothelial cells of the capillaries of the liver and the spleen (their 

 parenchymatous cells may also in certain cases manifest phagocytic 

 properties). Phagocytosis is found throughout the animal king- 

 dom. It occurs in all the contagious diseases that have been well 

 studied, not only in those of a particularly infectious nature, but 

 also in those that are preeminently toxic and in which bacterial 

 invasion is extremely limited. The tetanus bacillus and the 

 diphtheria bacillus, for example, are taken up and destroyed by 

 phagocytes. Phagocytes also play an essential role in chronic 

 bacterial infections, as the constitution of the tubercle indicates. 



Phagocytes do not limit their activities to the taking up of living 

 or dead microbes. They may also capture spores and prevent their 

 germination. Their activity may also be utilized against other 

 foreign bodies and against the other cells of the same animal when 

 they have become useless or even harmful and are destined to 

 disappear. The protoplasm of phagocytes likewise takes up soluble 

 substances introduced into the body, as was shown by the researches 

 of Samoiloff,t and of Lipski,J (Pharmacological Institute of Dorpat) 

 on the distribution of iron and of silver as soluble compounds in the 

 animal body. 



What proves the very fundamental function of phagocytes in the 

 destruction of bacteria is the surprising rapidity with which the 

 engulfing of organisms may be accomplished, as several observers, 



* Eosinophilic leucocytes only rarely take up bacteria. Mesnil (Annales de 

 1'Institut Pasteur, May, 1895) has noted, in the frog, eosinophilic cells in the act 

 of engulfing anthrax bacilli. We have still more recently noted the taking up 

 of the diphtheria bacillus by the eosinophiles of a guinea-pig immunized by a 

 strong dose of anti-diphtheria serum. 



t Samoiloff, Arbeiten des pharmakologischen Institutes zu Dorpat, IX, 1893. 



t Lipski, Ibid. 



