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in the cultivation of Pfeiffer's bacillus but most of the methods 

 applicable to solid media can also be used for fluid media. 

 By ,.agar" is understood, when the contrary is not stated, 

 either the classical peptone broth agar or another medium 

 of similar constitution ((„tryp-agar", „vitamine agar" etc.). 



1. The classical medium for cultivating Pfeiffer's bacillus 

 is agar smeared with a thin layer of blood (Pfeif- 

 fep. (2)). Human and rabbit blood etc. were originally used 

 but Pfeiffer soon found that pigeon blood was specially sui- 

 table. Pfeiffer's pigeon blood agar has given useful results 

 in the hands of most investigators. During the last pandemic 

 Pfeiffer himself adhered to this medium 1 (Leichtentritt (1), 

 Loewenhardt (2)). Agar smeared with other animals' blood 

 and particularly with human blood must on the contrary be 

 deemed a bad medium. 



According to the experience of many authors (Gzaplewski, 

 Ellermann, Crofton, Wyard and a number of others) which 

 I quite agree with, agar mixed with blood gives a growth of 

 Pfeiffer's bacillus that perhaps is not exactly richer but at any 

 rate is more easily perceptible, and this applies also to pigeon 

 blood. 



2. Agar mixed with unaltered blood, for the sake 

 of brevity termed „blo*od agar", was undoubtedly the medium 

 most used until after the beginning of the last pandemic. The 

 first to give this method of preparation was Borchardt. 



The majority of authors even those that praised the me- 

 dium, have only got Pfeiffer's bacillus to grow however, both 

 on agar smeared with blood and on agar mixed with blood, in 

 very small colonies the size of a pin's head or there-abouts. 

 These tiny „dew-drop" colonies have indeed even been com- 

 monly described as the characteristic form of growth of Pfeif- 

 fer's bacillus and the larger colonies which were also ob- 

 served in the early days around foreign bacterical colonies, have 

 been called „gianl colonies". As is clear from the following, 

 Pfeiffer's bacillus grows on really good media always in the 

 form of these „giant colonies" which are naturally to be looked 

 upon as the normal form of growth. The growth described 

 as characteristic until the last few years can therefore only 

 be called a very stunted growth. 



A few authors (Williams, Crofton and others) have ob- 



