Apr. 12,1924 
Development of American Foulirood 
163 
until external transformation in form has begun, so that after death the pupa 
tongue is seen extended and often attached to the upper side wall of the cell in a 
characteristic manner (fig. 17.) It is possible that in such cases the initial 
inoculum was smaller than the average, thereby retarding maximum growth 
of the organism, as was noted in the cultural experiments, and delaying the 
production of sufficient toxin to kill until this stage of development had been 
reached. 
While the biochemical relations of the bee larva to the disease are seemingly 
quite adequate to explain the delay in the time when American foulbrood is 
manifest, there is one other consideration which should be mentioned. The 
ability of the larva to resist the invasion of the bacteria is a subject on which 
virtually nothing is known, yet there must be some such ability, as is suggested 
by the fact that a slight initial inoculum in a colony may not cause the disease 
to be manifest. At the time when the biochemical conditions are most favorable 
for the germination and growth of the invading organisms, 
the larva itself has reached that stage of its development 
when its internal structure is materially modified by 
histolysis in advance of pupation, and it must follow 
almost necessarily that its power of resistance is reduced. 
The extent to which this factor is involved is, for the time 
being, purely a matter of speculation. 
The variation in the content of reducing sugar of the 
healthy honeybee larva and the inhibition of the germi¬ 
nation and growth of Bacillus larvae by a concentration of 
over 3 or 4 per cent yield an interesting fact concerning 
the other serious disease of the brood of bees. European 
foulbrood makes its attack on the bee larva at an earlier 
stage in its development, while the content of reducing 
sugars is still high. It must, therefore, be concluded that 
Bacillus pluton has the ability to grow and rapidly to 
produce toxic substances sufficient to kill the larva in a 
medium of much higher reducing-sugar content than has Bacillus larvae , probably 
as high as 15 per cent. 
Fig. 17—Decomposed, dried 
down remains of pupa 
dead from American foul¬ 
brood, showing character¬ 
istic tongue attachment to 
upper wall of cell (White 
m 
THE EFFECTS OF BACTERIAL METABOLISM IN THE LARVA 
There is little unanimity of opinion concerning the effect of dextrose (glucose) 
upon nitrogen metabolism by various bacteria. Kendall and Walker (24) con¬ 
cluded that the presence of glucose in the medium delays the production of 
proteolytic enzym, indicating the “protein-sparing” action of carbohydrates. 
Fischer (23) believed that proteolytic enzym is inactivated by glucose, indicated 
by inhibition of indol formation. Berman and Rettger (6) state that the presence 
of a carbohydrate in a culture medium may inhibit protein metabolism, depending 
on the nature of the medium and ‘on the type of the organism as related to hydro¬ 
gen-ion concentration. DeBord (20) believes that some bacteria destroy glucose 
without marked increase in the hydrogen-ion concentration and that the rate of 
production of amino nitrogen or ammonia nitrogen, which may be affected by the 
presence of carbohydrates, indicates different types of metabolism of bacteria. 
The results of the present investigation, although more or less incomplete on 
this subject, seem to indicate that Bacillus larvae has the ability to decompose 
nitrogenous material in the presence of carbohydrate, since there must be dextrose 
available until the stored glycogen of the fat body is entirely hydrolyzed. 
Many organisms are unable to attack complex protein unless there is some other 
source of food present, because, according to Berman and Rettger (6), to be 
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