12 DISEASES OF BEES 



medium. He also showed that a number of other bacteria, which 

 occurred in larvae sick or dead of this disease {Streptococcus apis, 

 Bacterium eurydice, Bacillus alvei, Bacillus orpheus), would not 

 produce disease when introduced into healthy colonies of bees. 

 Since B. pluton would not grow, his evidence that it caused European 

 foul brood was based upon the fact that no bacterium cultured 

 from sick or dead larvae would cause the disease, and that all 

 attempts to show that a filterable virus was responsible for pro- 

 ducing the disease failed. Superficially this evidence was rather 

 unconvincing, and subsequently it aroused much criticism. Thus 

 White's hypothesis has been contested by Lochhead in Canada, by 

 Burnside at the Uftited States Department of Agriculture, by 

 Borchert in Germany, and formerly by myself. This confusion has 

 undoubtedly arisen through the failure of all these workers to 

 distinguish White's Bacillus pluton from the various species .of 

 " S. apis " with which it can readily be confused morphologically. 

 The fact that Bacillus pluton does exist as a species distinct from 

 " S. apis," and that it is practically certain that it causes European 

 foul brood, is apparent when the following experimental results 

 are considered. 



Three to four day old, apparently healthy larvae in colonies 

 badly affected with European foul brood frequently have 

 numbers of small lanceolate-shaped cocci in their intestinal tracts. 

 These cocci occur singly, or, more frequently, in pairs and short 

 chains, and at this early stage in infection are present in pure, or 

 apparently pure, culture in the gut of the affected larva. When the 

 whole intestine is removed, with aseptic precautions, from such a 

 larva, and attempts are made to culture this coccus from the whole 

 gut or portions of it on media suitable for the growth of most 

 bacteria occurring in larvae affected with brood disease, the coccus 

 fails to multiply. Very occasionally no bacteria grow under these 

 conditions, but more frequently other bacteria make their appear- 

 ance, notably small rod shaped bacteria [Bacterium eurydice) and 

 sometimes Bacillus alvei. These cocci correspond to the Bacillus 

 pluton described by White. 



Larvae which are obviously affected with European foul brood 

 always contain B. pluton-hke organisms in large numbers in their 

 intestinal tracts, and in nearly every case large numbers of other 

 bacteria are present simultaneously — the so-called secondary 

 invaders. Among these secondary invaders, normally the first to 

 appear is a small rod- shaped bacterium (Bacterium eurydice), but 

 " S. apis " species also frequently appear at this stage. However, 

 these " S. apis " species are by no means always present in affected 

 larvae. When present " S. apis " can be distinguished morphologi- 

 cally from B. pluton, though this distinction is by no means a 

 clear cut one, some measure of experience being necessary before 

 the two species can be readily differentiated. Normally the " S. 

 apis " type of cell is more spherical than B. pluton, Ihe latter being 



