662 JOURNAL OF ECONOMIC ENTOMOLOGY [Vol. 27 



accorded with those observed in naturally infected larvae and the micro- 

 scopical picture was typical — B. alvei forms being also present, though 

 only in small numbers." If Wharton's cultures were pure, as he as- 

 sumes, to him belongs the credit of first producing typical European 

 foulbrood by inoculation with pure cultures. 



The writer's inoculation experiments with 5". apis and with non-spore- 

 forming rod cultures (resembling B. eurydice) isolated from sick or dead 

 brood gave results that were largely negative or inconclusive. On one 

 occasion typical European foulbrood was produced by inoculation with 

 cultures of 6". apis freshly isolated from sick larvae. In isolating pure 

 cultures plating was ordinarily done two or more times. Occasionally 

 larvae inoculated with such cultures appeared to become infected and 

 were removed by the bees, but the symptoms were not typical of 

 European foulbrood and the infection disappeared promptly. 



In an experiment performed in 1933, bacteria from the digestive tract 

 of a naturally infected larva were streaked on egg-yolk-agar plates. 

 After 24 hours at 34° C. isolated colonies of S. apis were touched with a 

 platinum loop and cultures were prepared on egg-yolk-agar slants. With 

 the abundant growth obtained on these slants after 44 hours at 36° C, 

 a colony of black bees was inoculated by spraying the bacteria, in water 

 suspension, over two combs of young and hatching larvae. Two days 

 later numerous coccoid bacteria were found within the digestive tract 

 of some of the larvae. On the following day coccoid bacteria had greatly 

 increased in number in many of the inoculated larvae and larvae were 

 being removed rapidly by the bees. On the fourth day more than 90 

 per cent of the inoculated larvae had been removed. None of those 

 remaining showed outward symptoms, but upon microscopical exami- 

 nation coccoid bacteria morphologically identical with the bacteria in 

 the inoculum were so abundant within the digestive tract that infection 

 could be definitely ascertained. All the unsealed brood in the inoculated 

 combs was finally removed by the bees and no dead larvae were found 

 in the cells. 



A water suspension of bacteria from the artificially infected larvae was 

 next sprayed over another comb of young brood in the same colony. 

 After 3 days fully 25 per cent of the inoculated larvae in this comb were 

 dead or dying from infection, of which the gross symptoms and the 

 bacteriological picture were typical of European foulbrood. Pointed or 

 lancet-shaped cells {B. pluton) were at first absent or present only in 

 small numbers, but later they became numerous. The coccoid bacillus 

 was reisolated, but out of about 100 cultures B. alvei was obtained in 

 only one. With cultures prepared by rough transfer from those with 



