THE PATH OF EVOLUTION 



great as that possessed by the bacteria, enabling them 

 (the former) to move to the point that is attacked. 

 This faculty, designated by the name of Chemitaxia 

 (chimiotaxie), is positive or negative, attractive or re- 

 pulsive, as the substance varies. 



According to the view of other observers, the 

 leucocytes are only the scavengers who remove the 

 dead substances in the blood. The death of the 

 pathogenic microbes is due to the various humors of 

 the body, especially the serum of the blood, which 

 contains a toxine substance that is fatal to their life 

 and that acts thus as an antiseptic. Metchnikoif him- 

 self admits that it is probable the phagocytes are not 

 the only means of defense at the disposition of the 

 organism, and that several factors may jointly tend 

 to the same end. (Revue EncyclE*, 1891-1894.) 



The white corpuscles occur in great number in 

 the spleen, amounting normally to over one to twenty 

 of the red corpuscles. In this organ whose especial 

 function is yet unknown, and which permits life to 

 be sustained even after its removal the white cor- 

 puscles in disease, especially in some forms of anaemia, 

 amount to more than one to three of the red. The 

 spleen is the site of the ultimate removal of most of 

 the invading bacteria. Whether it is also the scene 

 of the formation of the white and red corpuscles, or 

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