254 



namely, Pfeiffer's bacillus, the haemolytic haemoglobinophilic 

 bacteria, and Bacillus haemoglobinophilus canis. 



Of these the first species only is to be regarded as hae- 

 moglobinophilic in the strictest sense. 



Besides these three well defined species a few strains have 

 been described which may possibly belong to same group. 



28. An account and criticism of the nutritive media which 

 have been used in the cultivation of Pfeiffer's bacillus has 

 been given. 



29. From my own experience and that of others it is 

 maintained that in all probability Pfeiffer's bacillus is not to 

 be looked upon as the primary specific virus of influenza. A 

 number of considerations of the conditions relating to its occur- 

 rence in the healthy and the sick, are also given. 



Our knowledge of the biology of the haemoglobinophilic 

 bacteria still requires to be widened in many directions. 



