56 



rally identical. Cecil & STEFFEN found the same thing in several 

 inoculation experiments in man. Valentine & Cooper and Po- 

 viTZKY & Denny made repeated investigations of the same persons, 

 some patients and some healthy carriers, and they usually found 

 the same type in all the examinations of the same person. In one 

 case the type remained unaltered after a year had passed. Some- 

 times however the type would change. It is reasonable to suppose 

 that this was due to its being superseded by another type. Thus 

 one case was observed where 49 out of 50 colonies from the same 

 inoculation, were of one type, and the remaining one, of another 

 type. On further investigation a couple of weeks later only the 

 last type was found. In a family it was observed that a certain 

 type was present in overwhelming numbers in each member, but 

 also in the case of several of them another type was present in 

 smaller numbers which was identical with the dominating type 

 in another member of the family. 



An observation exists however which seems to suggest a mar- 

 ked lability from a serological point of view. Anderson & Schultz 

 cultivated Pfeiffer's bacilli in a meningitis case from the spinal fluid, 

 blood, nose, throat, and naso-pharynx, and found them all different 

 by agglutination. They look upon it as improbable that the patient 

 was infected with 5 independent strains and draw the conclusion 

 that Pfeiffer's bacillus can easily change its agglutination reactions. 

 Unfortunately absorption experiments could not be earned out as 

 the different sera had been used up. They state they obtained better 

 results with agglutination when it was allowed 2 hours at 37° 

 and subsequent standing in the ice-safe than when incubated at 

 53° or 56° for a longer time, which is difficult to understand. It 

 is therefore feasible that Anderson & Schultz's curious results 

 are due to defective technique; but in any case they are so peculiar 

 and of such fundamental importance that as soon as the opportunity 

 occurs the experiments ought to be repeated. 



In view of the wide distribution of Pfeiffer's bacillus there is 

 nothing extravagant in the conception that a person may harbour 

 more than one strain. Thus Bell found as many as 3 different 

 strains in the same person, but 5 seems to be a rather large 

 number. For the present we must be sceptical that the same 

 strain of a bacterium may be different as regards agglutination 

 according as it is isolated from one or other site of the mucous 

 membrane of the upper air passages. 



General Classification. 



The biochemical reactions, just as the im'mune-reactions, 

 show that Pfeiffer's bacillus cannot be regarded as a single well- 

 defined bacterial type but rather that this name includes a 



