184 



PRIXCIPLES OF BACTERIOLOGY 



bodies is interesting both as showing the variation of the bacteria and 

 as one means of adapting themselves to resist destruction, since the 

 bacteria which ceased to produce agglutinable substance probably also 

 produced less substance with affinity for other antibodies. This inhi- 

 bition of the production of agglutinable substance was also very 

 noteworthy in the case of pneumococci grown in serum media. 



Relation between Agglutinating Bactericidal Power.- In spite of proof 

 to the contrary many good observers hold to the belief that there is 

 some relation between the agglutinating and the bactericidal strength 

 of a serum. The tests we carried out on the serum of a number of 

 horses showed no such relation. In Fig. 73 are recorded a num- 

 ber of comparative tests during a period of sixteen months. For the 

 tests of the bactericidal power of the serum we are indebted to Dr. Mary 

 E. Goodwin. She also showed that there was a production of group. 

 as well as specific immune bodies in the animals receiving prolonged 

 injections. The results of her experiments will be published later. 



1 and 2 



FiG. 73 

 3 and 4 5 and 6 7 and 8 9 and 10 11 and 12 13 and 14 15 and 16 



Relation of agglutinative power to bactericidal. Horse injected with Manila culture over a 

 period of sixteen months. 



Agglutination index. Bactericidal index. 



Tests dates. 



Variation in the Agglutinating Strength of a Serum. There is usually 

 a continued increase in the amount of agglutinin in the blood of an 

 infected person from the fourth day until convalescence and then a 

 decrease. At times, however, there is a marked variation from day to 

 day, so that it may be abundantly present one day and almost absent 

 the next. 



