4 THE CAUSE OF EUROPEAX FOUL BROOD. 



bers in samples of European foul brood. Feeding it in pure cultures 

 has so far given negative results. This organism, then, can also 

 be eliminated tentatively from the list of possible causes of this 

 disease. The other species, mentioned by Lambotte in 1902 as 

 Bacillus mesentericiis vulgaris, may be ^-aid to belong to a group of 

 bacteria found quite widely distributed in the apiary. Its infre- 

 quency in diseased brood and its occurrence in small numbers readily 

 eliminates this species from the list of possible causes. Most of the 

 bacteria that are met with in the study of European foul brood were 

 therefore excluded tentatively from the list of possible causes of the 

 disease. 



The possibility of an ultramicroscopic virus was also considered. 

 Brood sick or dead of European foul brood were removed from the 

 combs and crushed. An aqueous suspension of this diseased material 

 Avas then made in boiled water and filtered with the Berkefeld filter. 

 The filtrate remained clear when incubated at different temperatures 

 and cultures made from it produced no gi'owth. Separate filtrations 

 have been made of diseased brood received from various localities, but 

 in no instance where healthy colonies were fed filtrate obtained in 

 this way was European foul brood produced. The results of the ex- 

 periments therefore justify the tentative conclusion that there is no 

 filterable virus in European foul brood capable of producing the 

 disease. To this extent, then, has the possibility of an ultramicro- 

 scopic virus been eliminated. 



Having thus tentatively eliminated all the microscopically visible 

 organisms except Bacillus Y from the list of possible causes and like- 

 wise eleminated the probability of an ultramicroscopic virus, the 

 tentative conclusion was naturally reached that this remaining micro- 

 organism probably plays an imix)rtant role in the etiology of Euro- 

 pean foul brood. Such a conclusion was all the more imperative 

 since this organism had been encountered so frequently in the brood 

 of this disease and since, moreover, there had been no other factor 

 observed to Avhich the exciting cause could be attributed. 



SYMPTOMS MANIFKSTED BY LARV.T: SICK OF EUROPEAN FOUL BROOD. 



This conclusion led to a more extended study of this microorganism 

 in the disease produced experimentally. The presence of disease 

 can usually be detected in the experimental colony during the week 

 that the feeding is begun. The first indication of it may be that 

 only a portion of a larva is seen in a cell (fig. 1), the remaining por- 

 tion having been removed bv the bees. Aside from an observation 

 of this kind the earliest indication one gets from the macroscopic 

 (gross) examination is that sick larvae are found among the uncapped 

 brood. One should acquaint himself, therefore, with certain symp- 

 toms or signs manifested by sick larva? during the course of the dis- 



