70 HISTORICAL NOTES ON BEE DISEASES. 
uniformity in the microscopic findings. There were medium-sized 
and small bacterial rods present together with forms resembling in 
morphology Bactervum giintherr. There was 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 
eroup 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 alver 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-forms. 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- 
thera 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 larve attacked are characterized by the following symptoms: (a) More or 
less noticeable sour 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 larvee are characterized by the 
presence of forms resembling sour milk bacteria (gtintheri-forms) 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 sour milk bacteria and the giintheri-forms. 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 gtintheri-forms 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 
typical sour broody cells instead of the gtintheri-forms 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 affirmed that foul brood bacteria, sour brood giintheri-forms, and the 
