EUROPEAN FOULBROOD. ll 
finally filling it more or less completely (Pl. VII, J). The growth does 
not always take place uniformly along the peritrophic membrane (PI. 
VII, J), nor does it extend beyond it (Pl. VII, I, J, K), but is inclosed 
within the sac, the tissues of the larve not being reached. The mul- 
tiplication of the organism after the death of the host, if, indeed, it 
takes place at all, is limited. 
Secondary invaders, chiefly Bacillus alvei, Bacterium curydice, 
Streptococcus apis, and occasionally Bacillus orpheus, and a few 
others, are encountered at various stages of the disease and during the 
decay of the larva. During the life of the larva these species also 
remain within the peritrophic sac. 
BACILLUS ALVEI 
Bacillus alvei (fig. 2; Pl. VII, D, F) is present very frequently and 
in very large numbers in larve dead of European foulbrood. The 
species was well described by 
Cheyne (4). Descriptions may be 
found elsewhere also (11,18). It 
is readily recognized and may be 
differentiated easily from other 
spore - producing species  occa- 
sionally encountered in the dis- 
eased brood. 
Bacillus alvei is not the active 
cause of any bee disease. It 
seems probable, however, that it 
plays a role in European foul- 
brood, but the extent is not fully 
known. The species 18 present Fic. 2.—Bacillus alvei. Spores free from 
usually, if not invariably, in large Toto ueere mua 
numbers in the rubberlike scales (Pl. V, F, I), which resemble 
so much those of American foulbrood. The decayed larval mass, 
which forms the scale, before becoming dry is ropy in consistency 
similar to that of American foulbrood but to a less degree. It 
seems probable that this ropiness is due more or less directly to 
Bacillus alvet. On account of this viscidity the decaying mass, as 
well as the scales, are removed with greater difficulty than are most 
larvee dead of European foulbrood. The result, as often observed, is 
that these brown viscid decaying larve or the rubberlike scales result- 
ing from them are the only evidence that European foulbrood is 
present in the colony. 
While Bacillus pluton in such larval masses and scales is often diffi- 
cult to detect microscopically, its presence can be demonstrated 
through the experimental inoculation of healthy larve. Inasmuch as 
Bacillus pluton will live for a considerable period in the scales, it 
