550 INFECTION AND IMMUNITY. 



nating power for these strains than for non-patho- 

 genic varieties, and the converse is also true. There 

 are, however, many variations in the agglutinabil- 

 ity of the members in each group, a fact which in- 

 dicates variations in the receptor complex of the 

 different strains. It has been suggested that a 

 polyvalent serum obtained by immunization with 

 a sufficient variety of pathogenic strains will be 

 efficient in differentiating the latter from non- 

 pathogenic varieties by means of the agglutina- 

 tion test. 



Wright, noting an increase in the agglutinating 

 power when patients are treated by his method, 

 considers that this increase is an index of the im- 

 munity which is established. 



IV. MICROCOCCUS CATARRHALIS. 



For some years diplococci resembling the gono- 

 coccus and the meningococcus morphologically and 

 in staining reactions have been found in the spu- 

 tum by a number of observers, and to this coccus 

 Pfeiffer gave the name of Micrococcus catarrhalis, 

 It is frequently found in the respiratory passages 

 in influenza-like infections and other inflamma- 

 tory conditions, and occasionally in lobular pneu- 

 monia. It may be associated with the influenza 

 bacillus or the pneumococcus. Among 140 cases 

 of diseases of the respiratory passages Ghon and H. 

 Pfeiffer found it 81 times, and M. Neisser demon- 

 strated it in 16 cases of whooping-cough, in 

 one of measles and scarlet fever, and in 

 two of diphtheria. It loses significance in relation 

 to these diseases, however, since Jiindell found it 

 frequently in the mucus of the normal trachea, 

 and Weichselbaum cultivated it frequently from 



