EUROPEAN FOTJLBROOD. 9 



For a decade and a half following the observation the belief was 

 quite general that this bacterium was the exciting cause of a bee dis- 

 ease. The view was then seriously challenged. In 1906 the only 

 positive conclusion in regard to the relation between European foul- 

 brood and Bacillus aivei that could be drawn by the writer (13) was 

 that this species occurs in brood dead of the disease. 



William E. Howard (6), of Texas, after a brief study of the dis- 

 ease reported in 1900 the presence of an organism which he called 

 Bacillus miUli. He cultivated the species apparently with ease. In 

 1904 Bahr (1) in Denmark found a small oval bacterium in a brood 

 disease in which larvai dying in uncapped cells are yellowish in color 

 and not ropy in consistency. Burri (3) in 1906 encountered in his 

 studies on the brood diseases a small bacterium which he referred to 

 as guntheri-iorms,. The species was cultured and compared with 

 Baeterium guntheri and found to be somewhat different. In 1907 

 Maassen (7) obtained from brood material cultures of a species 

 which he named Streptococcus apis. White (14) in 1908 reported 

 the presence of a small organism in European foulbrood which had 

 refused to grow on artificial media. The species was not the one, 

 therefore, with which the investigators just referred to had worked. 

 That this organism might be the exciting cause of the disease was 

 noted. Pending more information regarding it, the species was not 

 given a name biit was referred to as bacillus " Y." That this species 

 bears a direct etiological relation to the disease was demonstrated in 

 1912 by the writer (15) and the name Baoilhis pluton was then given 

 to it. 



As the cultivation of Bacillus pluton on artificial media had not 

 been accomplished the conclusion that it is the exciting cause of 

 European foulbrood was arrived at by eliminating all other possible 

 agencies. The observations furnishing the proof appear in an earlier 

 paper (15). By demonstrating Bacillus pluton to be the cause of 

 the disease, Bacillus alvei, Streptococcus apis, Bacterium eu/rydice, 

 and Bacillus orpheus, and still other species occasionally encountered, 

 were thereby proven, to be secondary invaders. 



To eliminate the possibility of a filterable virus in European foul- 

 brood 10 colonies were inoculated with filtrates obtained from aque- 

 ous suspensions of brood sick and dead of the disease. In six 

 instances the Berkefeld N filter was used and in four the Pasteur- 

 Chamberland F was employed. In no case was the disease produced. 

 Studies recorded in the present paper on the resistance of Bacilhos 

 pluton to heating, drying, fermentation, and disinfectants show that 

 when the virus of the disease is not destroyed this species is still alive. 

 This fact is further evidence in support of the conclusion that the 

 species Bacillus pluton is the virus of the disease. 

 132817°— 20— Bull. 810 2 



