70 HISTOEICAL NOTES ON BEE DISEASES. 



uniformity in the microscopic findings. There were medium-sized 

 and small bacterial rods present together with forms resembling in 

 morphology Bacterium guntheri. There w^as an absence of spores 

 and of the corresponding vegetative forms. It was observed that 

 one group of bacteria may predominate in some samples and another 

 group may predominate in others. Where rods of relatively large 

 size were found in brood which in gross appearance resembled sour 

 brood, it was supposed that a double or mixed infection of foul brood 

 and sour brood was present. This double infection, it was believed, 

 occurred very frequently. 



In continuing his bacteriological study of "sour brood" Burri 

 encountered a few rather interesting species. Bacillus alvei was pres- 

 ent in many samples of "sour brood" examined. From most of the 

 samples examined difficulty was encountered in obtaining cultures 

 of the microorganism to which he refers as the giintheri-iorms. He 

 reports, however, that this difficulty had been overcome and that he 

 had obtained pure cultures of this species. He made some compari- 

 sons between the cultures of this species and those of Bacterium giin- 

 theri which resulted in the conclusion that while there was a certain 

 relationship existing between them, the two were not the same. 



Burri sums up the results of his study of "sour brood" as follows: 



1. There is a disease of the brood accompanied by a rapid growth of bacteria, which 

 have no direct relation with the bacteria of foul brood. 



2. The larvse attacked are characterized by the following Bymptoms: (a) More or 

 less noticeable soiir odor; (b) comparatively pale, dirty yellow color; and (c) a great 

 resistance of the chitinous covering which allows the dead larva to be lifted intact 

 from the cell as a moist mass. 



3. In microscopic examination the contents of these larvse are characterized by the 

 presence of forms resembling sour milk bacteria (guniheri-ionns) beside medium -sized 

 and small rods. It is characterized also by the absence of large spore-bearing rods 

 and spores. 



4. Pure culture experiments with such bacterial material give proof of a certain 

 relationship between the true Bour milk bacteria and the guntheri-iorvaa. The cul- 

 tures also show that the medium-sized and small rods are strong acid producers. The 

 name "sour brood" is therefore entirely justified. 



With respect to the occurrence of "foul brood" and "sour brood" 

 in the same colony one finds the following in Burri's paper: 



In describing each attempt to isolate the sour brood guntheri-iorma the rarely 

 expected fact was demonstrated that in a whole series of cases, a growth of colonies of 

 Bacillus alvei, the easily cultivated producer of stinking foul brood, was obtained from 

 tyi^ical sour broody cells instead of the giintheri-iorms desired . The series of cases of 

 this kind could be greatly increased. Moreover, in the course of my investigations 

 such findings have been repeated such a surprising number of times that I was forced 

 to think there must be some close connection between the two diseases. For some 

 time I was even inclined to believe that the sour brood bacteria represented only a 

 certain stage of development in the foul brood bacteria but gave up this view when 

 the morphological question was explained by means of culture experiments. To-day 

 it can safely be afiirmed that foul brood bacteria, sour brood guntheri-ioiiaa, and the 



