IMMUNITY AND SUSCEPTIBILITY. IOI 



have been thought to depend upon various causes. 

 Behring and Nissen 1 supposed that the white rat was 

 able to resist anthrax because of the extreme degree of 

 alkalinity of its blood. They were supported in their 

 views by Paul, 2 who found that alkaline solutions (i : 

 3000 sodium carbonate) acted upon the anthrax bacilli 

 like the blood of the rat ; and further, that if the rabbit's 

 blood is neutralized, it loses its germicidal power. Von 

 Foder also demonstrated that the resistance of the rabbit 

 to anthrax is increased by the injection of alkali into the 

 circulation, and that with this increased resistance the 

 germicidal activity of the blood increases. He also found 

 that when a rabbit is infected with anthrax there is a 

 natural increase in the alkalinity of the blood during the 

 first twenty-four hours, " when we may suppose that the 

 powers of nature are brought to bear upon and resist the 

 invading parasite;" and that with the further progress 

 of the infection it rapidly diminishes. 



Hankin believed immunity to depend upon certain 

 germicidal globulins which he isolated from the blood 

 serum of rats. Vaughan, 3 McClintock, and Novy attri- 

 bute the germicidal action of the blood to nucleins which 

 it contains in solution, and point out that the relationship 

 of alkalinity of the serum to immunity probably depends 

 upon the ready solubility of the nucleins in alkaline 

 solutions. 



To the bactericidal substances present in the blood 

 Buchner has applied the term Alexins. Hankin 4 calls 

 them defensive proteids. They are destroyed by heating 

 for one-half to one hour to 55°-6o° C, and are robbed of 

 activity by dilution with eight to ten volumes of distilled 

 water, though they can stand that dilution with physio- 

 logic salt solution. They can be precipitated from the 

 blood by the addition of forty per cent, of sodium sul- 



1 Zeitschrift fiir Hygiene, 1890, Bd. vii. 



* Proceedings of the Royal Society of London, May 22, 1890. 



• Medical A T eivs, Dec, 1893. 



4 Centralbl. f. Bakt. u. Parasitenk., xii., Nos. 22 and 23; xiv., No. 25. 



