528 BIOLOGY OF PNEUMOCOCCUS 



and heated for three hours at 60°," thus favoring the use of killed 

 suspensions. Issaeff 673 reported successful immunization of rabbits 

 by administering killed bouillon cultures and later blood from in- 

 fected animals, the organisms being first killed by chloroform or 

 heat. In immunizing horses, Denys (1897) 312 injected first heated, 

 then unheated cultures, next the blood of a rabbit dead of pneumo- 

 coccal infection, and finally living broth cultures. He thus was able 

 ultimately to inject a large amount of an extremely virulent cul- 

 ture without causing any more marked symptoms than a transient 

 rise in temperature. Mennes (1897), 893 by using methods similar to 

 those of Denys, produced in the horse after three or four months' 

 treatment, serum that exhibited preventive, curative, and "anti- 

 toxic" properties. Washbourn (1897) 1487 immunized ponies by the 

 subcutaneous injection of heated broth cultures, then living agar 

 cultures, and finally living broth cultures. After nine months of 

 treatment, the serum was found to possess marked protective ac- 

 tion. 



Neufeld (1902) 974 recommended the use first of killed, then of 

 living organisms. Later, however, with Haendel (1909), 989 Neufeld 

 stated that in immunizing horses and asses there was no such 

 marked difference between the use of living and dead organisms as 

 was found in rabbits, although horses injected with viable cultures 

 produced better serum. Horses proved to be more sensitive than 

 asses to living organisms. 



For developing antipneumococcic serum of high protective titer 

 in horses, Dochez (1912) 316 employed large doses of living, viru- 

 lent organisms. In an investigation of the action of immune serum 

 on pneumococcal infection in rabbits, Wadsworth (1912) 1458 

 found that little or no curative effect was exerted by serum from 

 animals immunized with washed, dead organisms or culture fil- 

 trates ; only after immunization with living, virulent cultures did 

 the serum acquire marked therapeutic properties. In a study on 

 the distribution of immune bodies in antipneumococcic serum, 

 Avery 82 immunized horses over periods of one or two years by in- 



