211 



examination gave comparatively weak reactions, were again tested 

 in the las I part of the experiment. 



Of the 75 strains, 10 were agglutinated at 1 : 10000, 20 at 1 : 14000, 

 37 at 1 : 201 00 and 8 at 1 : 28000. A small number of these are mean 

 values of two experiments with the same strain. In a few cases 

 the agglutination titers of the two tests varied as much as 1 : 7000 

 and 1 : 20000. Four of the experiments recorded are repetitions of 

 experiments which gave only slight agglutination even in the stronger 

 serum concentrations; no special divergencies were found in the 

 case of these strains in the repetition of the test. 



Al the strains were also investigated in an earlier experiment 

 which on account of technical deficiency, will not be further dis- 

 cussed; the strains which in the experiment recorded only gave 

 comparatively weak reactions, did not depart in this experiment 

 from the others with regard to the strength of the agglutination. 



Later, a further 26 strains of the whooping-cough bacillus were 

 agglutinated by the same serum with the same results. 



In the agglutination experiments with the whooping-cough 

 bacillus no certain difference could therefore be observed 

 between any of the strains. 



The 75 strains, with the exception of one which had died 

 out, were then examined in the following way. 



On inoculation on blood agar the strains that had only 

 been grown a comparatively short time, gave a little weaker 

 growth than the others, but otherwise no difference whatever 

 in the macroscopic appearance of the cultures, which will 

 not be described in detail here, could be seen. It need only 

 be remarked that none of the strains had a tendency to spread 

 over the surface as is so often seen in Pfeiffer's bacillus, and 

 that I have never met with any pure culture either of Pfeif- 

 fer's bacillus or other bacteria which by comparison with 

 a growth of the whooping-cough bacillus on blood agar could 

 be mistaken for the latter. All the strains grew distinctly 

 more slowly than Pfeiffer's bacillus. In all cases there 

 appeared, after a couple of days growth, a relatively exten- 

 sive ill-defined haemolysis of the blood agar, very 

 different in appearance from that of the „haemolytic, haemo- 

 globinophilic bacilli". 



On microscopic examination all the strains were de- 

 cidedly Gram negative. The one that had been cultivated longest 

 in vitro, namely for about a year and a half, and with which 

 the serum mentioned was made, was distinctly rod-shaped. 



14* 



