408 BIOLOGY OF PNEUMOCOCCUS 



jected intraperitoneally into mice weighing 18 to 20 grams two 

 to three hours before giving an intraperitoneal inoculation of 

 varying amounts of virulent broth cultures. Later, when more po- 

 tent serum became available, falling amounts of serum were in- 

 jected into mice just previous to inoculation with one or more 

 multiples of the minimal infecting dose. Ungermann and Kan- 

 diba 1438 applied the Neufeld and Haendel technique to a study of 

 the quantitative relations between the protective strength of im- 

 mune serum and the amount of culture used, and discovered that 

 the action of the serum failed to follow the law of multiple propor- 

 tions. When the tests were performed on rabbits, there appeared to 

 be a definite relation between the volume of serum and the weight 

 of the animal, called by Ungermann and Kandiba (1912) the 

 Schwellenwert or threshold value. Above this value serum pro- 

 tected against many multiples of the minimal lethal dose of cul- 

 ture, but below the threshold the serum had little if any action. In 

 their experience, Neufeld and Haendel (1912) 993 found that, in 

 order to ensure protection with serum, it was necessary to cross 

 the hypothetical threshold and to administer large volumes of 

 serum. 



SPECIFICITY 



Some claims have been advanced concerning the lack of type- 

 specificity in the protective mechanism. For example, Yoshioka 

 (1923) 1561 reported that mice that had survived an intraperitoneal 

 inoculation of pneumococci were protected against an intraperi- 

 toneal injection three or four days later of cultures of heterolo- 

 gous type. Furthermore, mice similarly treated were able to with- 

 stand inoculation with streptococci, while large doses of killed 

 staphylococci produced definite protection against pneumococci. 

 Yoshioka also noted a certain degree of cross-protection in guinea 

 pigs and rabbits after pneumococcal infection. Kolchin and Gross 

 (1924*) 739 observed cross-protection for Type III strains in a sam- 

 ple of Felton's monovalent Type I antipneumococcic serum. Mono- 



