IMMUNITY AND SUSCEPTIBILITY. 99 



it necessary for him to lay aside the idea of phagocytosis. 

 He still believes these cells to be the essential agents, 

 whether it be by incorporating and digesting the bacteria 

 or by excreting products that annul their poisons. 



II. The Activity of the Humors. — The uncer- 

 tainty regarding the ability of the phagocytes to destroy 

 bacteria, and the probability that the bacteria are already 

 dead when they incorporate them, oblige us to look else- 

 where for the causes of bacterial death and immunity to 

 their toxins. If the cells do not perform the function, 

 may it be the juices of the body ? As early as 1884 Groh- 

 man observed that fresh blood serum had the power of 

 attenuatingthe anthrax bacillus ; and in 1887 von Fodor * 

 found that by a more prolonged exposure to its influence 

 the bacilli were killed. The matter was carefully studied 

 by Nuttall 2 in 1888, and he and Buchner 3 found that 

 bacteriolysis was a power common to many of the body 

 juices. Nuttall investigated blood serum, aqueous humor, 

 and serous fluids of the body, and found them all germi- 

 cidal; while Buchner showed that in the blood the power 

 resided exclusively in the serum, was not destroyed by 

 dilution, and was not dialyzable. Nuttall found that the 

 destruction of anthrax bacilli by rabbits' blood required 

 from two to four hours, the temperature of 37 C. being 

 maintained. Bacillus subtilis and Bacillus megatherium 

 were also destroyed by the fresh serum, but Staphylococ- 

 cus pyogenes aureus was not. Prudden found that hy- 

 drocele fluid and abdominal effusions also possess germi- 

 cidal powers. 



The germicidal power of the blood is not a permanent 

 quality, but passes away in a day or two, and can be 

 entirely set aside at any time by heating to 55 C. 



All bloods do not have the same degree of destroying 



1 Cenlralbl.f. Bakt. u. Parasitenk., 1890, vii., p. 753. 



* Zeitschrift fur Hygiene, 1 888, iv., p. 353. 



* Centralbl. f. Bakt. u. Parasitenk, Bd. v., p. 817; Bd. vi., p. I, 561 ; xii ; 

 No. 24, 1892. Berliner klin. Wochenschrift, 1892, p. 449. Munchener med. 

 Wochemchrift, 189.2, Nos. 8 and 52 ; 1894, Nos. 24 and 25, pp. 717 and 744. 



