Apr. 12, 1924 
Development of American Foulbrood 
133 
death of the larva in the intestinal tract and usually kills before sealing takes 
place, as differentiated from American foulbrood as described above. Unfor¬ 
tunately, as yet it has been impossible to grow this organism in pure culture on 
artificial culture media. 
Further work has been done by various investigators on certain laboratory 
phases of the bacteriology and diagnosis of the two diseases, but no additional 
information has been obtained concerning the etiological and biochemical rela¬ 
tionships of the causative organisms which would aid in the solution of the 
present problem. 
BASIS FOR INVESTIGATIONS 
Throughout all the discussion of symptoms of the brood diseases in the litera¬ 
ture, particularly in relation to the different ages at which the diseases attack 
during the life history of the larvae, there has been no adequate explanation of 
the reason for this apparent fundamental difference. 
Maassen (28) in the case of American foulbrood made the observation that, 
“according to the microscopic findings from section preparations, Bacillus 
brandenburgiensis [Bacillus larvae] does not come to luxuriant development in 
the intestine of the larva, though this is the case with Bacillus alvei and with 
Streptococcus apis [in ‘sourbrood’]. It finds much more promising nourishment 
in the fat bodies of the larva. Apparently the bacillus finds opportunity to press 
its way into the fat bodies shortly before the pupation of the bee, at the begin¬ 
ning of the natural changes in the intestinal tube. From this it seems clear 
why the larvae containing Bacillus brandenburgiensis die after sealing.” In part 
this is probably correct, since it may easily be observed that soon after capping the 
tissues of the healthy larva become more or less granular and watery in consistency > 
at which time it is almost impossible to distinguish the intestinal tract. It is also 
difficult to remove the larva in this condition from the cell without rupturing the 
skin envelope. This process is described more in detail later. It does not 
explain, however, why the spores of Bacillus larvae do not germinate and increase 
in numbers sufficiently to kill the larva much earlier during the feeding period, 
as in the case of European foulbrood. A vague and only partially correct sug¬ 
gestion was given in an earlier paper by the writer (46), in which the following 
theory was stated: “Bacillus larvae gains entrance to the larva generally in the 
spore stage, in the larval food. This occurs at about the same stage as in Euro¬ 
pean foulbrood, while the larva is still coiled in the cell. Only rarely, however, 
do coiled larvae die. This is apparently because it takes some time for the rest¬ 
ing stage spores to germinate into the active vegetative rods. This causes death, 
as a rule, to occur later in the life history of the larva.” 
RELATION OF THE BROOD DISEASES TO THE LIFE HISTORY OF THE 
HONEYBEE LARVA 
The development of the honeybee may be divided in general as follows: After 
the egg is laid there is a period of three day’s incubation before it hatches into 
the larva. The larval stage, during which active feeding and growth occur, 
comprises four and a half to five and a half or six days. At the end of the feeding 
period the larva is sealed in the cell, where it spins its cocoon. Metamorphosis 
then occurs, and the fully formed adult bee emerges in about 12 days, making a 
complete developmental period of approximately 21 days. According to White 
(58 ), there is a prepupal period in healthy brood of four days after sealing occurs 
before the actual change in the external form to that of the adult bee takes place. 
During the first two days after capping, the larva is active in the cell, consuming 
any remaining food and spinning a cocoon. Some time during this period ac¬ 
cording to Straus (48 ), or just previous to capping according to Zander (57), 
