468 PATHOGENIC MICROORGANISMS 



with irregular results. The rational beginning based on the recog- 

 nition of different pneumococcus types was made by Neufeld and 

 Haendel in Germany, and carried to a considerable degree of success 

 by Cole and his associates at the Rockefeller Hospital in New York. 

 By the immunization of horses with the various types of pneumococci 

 mentioned above, considerable success has attended the use of sera 

 produced with Type I, and less success but great promise, that of sera 

 produced with Type II. The injection of considerable quantities of 

 the homologous sera intravenously at least aids in sterilizing the blood 

 stream, and upon this the eventual outcome of many cases may depend. 



The actual method of producing serum at the present time depends 

 upon the injection of horses with, at first, killed cultures and then 

 living pneumococci. Horses are used as in other serum production, 

 and all the preliminary precautions against glanders and tetanus 

 taken. The pneumococci used are, of course, typed, since, as we shall 

 see below, type I serum is the only one that so far has yielded at least 

 hopeful results. The organisms are grown on suitable broth, and 

 young cultures are injected. For the early injections the organisms 

 are killed by heating from 56 to 60. The method of Cole is to inject 

 daily for six days the killed bacteria thrown down from 50 c.c. of a 

 12-hour broth culture. A rest of a week is then given, and the serum 

 of the horse tested for agglutination. A second series of dead culture 

 injections is then carried out, and again an interval allowed. Again a 

 test is made, and if agglutination is as high as 1200, and 0.2 c.c. 

 protects a mouse against 0.1 c.c. of a virulent culture, the serum could 

 be used, but Cole states that this is not often the case. After the 

 second series of dead culture injections, living bacteria are injected; 

 three injections containing bacteria from 2.5 c.c. of the original culture 

 are then given. The actual methods of injecting horses will vary with 

 individual experience in different places, but in all cases the principle 

 is the old one of first injecting the living cultures with great care not 

 to infect the horse, and bleeding determined by preliminary test. 



The horses are bled in the usual way, and the serum obtained. The 

 serum is taken up, stored, and handled as in the case of other pro- 

 tective sera. 



Recently a great deal of very interesting work has been done upon 

 the relative purification of pneumococcus anti-sera from horse protein 

 by attempts to isolate the antibodies from whole serum. Gay and 

 Chickering 87 precipitated dissolved pneumococcus antigen with anti- 



8T Gay and Chickering, Jour. Exper. Med., 21, 1915, 389. 



