Immunity acquired by natural means 441 



1892, the new data began to be applied to that disease. We have 

 already referred in a preceding chapter to the fact that the blood 

 serum or the blood of those in good health and who have never had 

 Asiatic cholera, is capable of preventing cholera peritonitis in the 

 guinea-pig inoculated with Koch's vibrios. In order to obtain this 

 protective action, the injection of a pretty large dose, about half a c.c., 

 is necessary. This property is in no sense specific, for the same 

 blood, injected in the same doses into guinea-pigs, will protect 

 them not only against this vibrio, but also, and indifferently, against 

 many other bacteria, such as the typhoid coccobacillus, the Bacillus 

 coU. etc. 



The blood or blood serum, coming from those who have recovered 

 from Asiatic cholera, may, on the other hand, acquire a specific 

 protective power. It will, indeed, prevent infections by other micro- 

 organisms ; but, to obtain this effect, it is necessary to inject the same 

 quantities of it as of the blood coming from normal individuals. On 

 the other hand, when we wish to prevent cholera peritonitis in the 

 guinea-pig, we need introduce minute doses only of the serum of 

 persons who have recovered from an attack of cholera, Lazarus 1 was 

 the first to make this interesting observation. In three cases of 

 cholera studied by him, the serum withdrawn some time after recovery 

 exhibited an extraordinary protective power : a decimilligramme of 

 the blood serum of these patients was quite sufficient to prevent the 

 death of a guinea-pig inoculated intraperitoneally with the cholera 

 vibrio. Soon after, G. Klemperer 2 made a similar observation in two 

 other cases that had recovered, but the blood, in his convalescents, 

 was much less active than was that in the cases cited by Lazarus. 



Issaeff 3 , working in Koch's Institute in Berlin, examined the blood 

 of several persons who had recovered from cholera, and found that [463] 

 the serum had always acquired a specific protective property ; this 

 property never developed before the third week from the commence- 

 ment of the disease, and had completely disappeared as early as 

 three months after this period. Several examples studied by 

 A. Wassermann 4 and Sobernheim 5 fully corroborate this conclusion. 

 Our own researches 6 on twenty-four cases indicate a very great 



1 Berl klin. Wchnschr., 1892, S. 1072; 1893, S. 1241. 

 * Berl klin. Wchnschr., 1892, S. 1267. 



3 Ztschr.f. Hyg., Leipzig, 1894, Bd. xvi, S. 308. 



4 Ztschr.f. Hyg., Leipzig, 1893, Bd. xiv, S. 42. 



5 Hyg. Rundsch., Berlin, 1895, S. 145. 



6 Ann. de I'Inst. Pasteur, Paris, 1893, t. vn, p. 417. 



