118 STUDIES IN IMMUNITY. 



portions with normal horse serum instead of preventive serum. 

 Streptococci grown in these media, however, show certain peculiari- 

 ties that may be noted. 



In both these mixtures of normal rabbit serum and either normal 

 or immune horse serum the growth begins rapidly if the cultures 

 inoculated are young. An equal and considerable growth is evident 

 three hours after inoculation. In the tube containing the normal 

 horse serum the streptococci are in numerous short chains; in the 

 other, containing preventive serum, they form much fewer and 

 longer chains and these chains are frequently coiled. There is a 

 difference then in the arrangement of the cocci, although the total 

 number is about the same in either medium. 



After 5J hours these same characteristics are still present. Later 

 on (19 hours after inoculation) the chains become longer in the tube 

 containing normal serum, so that the difference in length of chains 

 between the two tubes is less manifest. There is still no difference 

 to be noted in the richness of the culture. We have found no 

 retarding property on growing streptococci in antistreptococcus 

 horse serum any more than did Denys and Marchand.* 



If in such an experiment a less virulent streptococcus is used 

 (one that kills a rabbit in a dose of 0.25 of a cubic centimeter in- 

 travenously), similar results are obtained; with such an organism, 

 however, the difference in the length of the chains is much less. 



The injection of 10 c.c. of preventive serum in a normal rabbit 

 does not endow this animal's serum with any bactericidal power. 

 The serum 25 hours after injection is just as good as a culture 

 medium for streptococcus as before the injection of antistrepto- 

 coccus serum. In both of them it grows rapidly and well. 



Antistreptococcus serum has a slight but distinct agglutinating 

 property. We demonstrated in 1895 that a trace of a preventive 

 cholera serum, when introduced in a fluid containing cholera 

 vibrios in suspension, produces in a very short time their immobiliza- 

 tion, and clumps them into distinct masses that stand out as white 

 points in a clarified fluid. This is the invariable effect of this pre- 

 ventive serum. The following year Gruber and Durham noted a 

 similar fact, not only with vibrios, but also with B. typhosus and 



* Denys and Marchand, Immunity conferee au lapin par 1'injection de se'rum 

 anti-streptococcique de cheval. Bull. Academic royale de Belgique, 1896. 



