244 



to other drastic procedures (acid treatment, pepsin digestion, 

 etc.) these differences pass away and good results can usually 

 be got with the blood of any of the animals mentioned. For 

 instance Levinthal found that the blood of all the species 

 of animals investigated was uqually suitable for his medium. 

 The reason that Messerschmidt, Hundeshagen, &Scheer found 

 sheep blood unsuitable for this purpose is given by Levinthal 

 as due to the fact that „Wassermann animals" were used which 

 from frequent bleeding had become anaemic, and he points 

 out that some workers principally used sheep blood for making 

 Levinthal agar. 



Rivers (1) found, on comparing a large number of samples 

 of human blood with rabbit and guinea-pig blood, that human 

 blood contained a bactericidal, growth-inhibiting substance in 

 considerably greater concentration than the other two. This 

 substance was destroyed by half an hour's heating 54°— 36°. 



Gosio and Gosio & Missiroli, in spite of numerous trials 

 with the blood of the most different species of birds and mam- 

 mals, could only obtain a good growth of Pfeiffer's bacillus 

 on pigeon, dove, and plover blood. They even advanced Hie 

 view that the Pfeiffer's bacilli which other authors declared 

 they had cultivated on other media were Regenerated". 



Prof. Gosio has been kind enough to send me two strains 

 of his typical Pfeiffer's bacilli (already referred to as „R 1" 

 and „R 2") that had however been grown for 2 years in vitro, 

 which, according to Gosio, entails a certain amount of training 

 to the blood of other animal species. When cultivated on 

 Fildes agar and various other media these two strains 

 grew exactly like other typical Pfeiffer's bacilli. As 

 the power of adaptation of Pfeiffer's bacillus to a nutritive 

 medium in vitro seems to be very limited it is improbable that 

 these strains were originally quite different from all those I 

 isolated. The enormous material of Pfeiffer's bacillus which, 

 all over the world, has been cultivated on other media than 

 pigeon blood agar, discountenances however, without going 

 any further, Gosio's view that true Pfeiffer's bacilli should 

 be limited to those that only grow on media containing pigeon 

 blood There is no reason to believe that Gosio's Pfeiffer's 

 bacilli were different as regards their nutritive requirements 

 from those that other investigators have worked with. He 



