August 16, 1912] 



SCIENCE 



221 



such a temperature might be favorable for 

 growth, because we found that a certain num- 

 ber of our caterpillars died from " flacherie " 

 throughout the winter whenever we allowed 

 the temperature to rise sufficiently in the in- 

 sectary. Furthermore, our field experience 

 later in the season clearly desionstrated to us 

 that more caterpillars die of " flacherie " on a 

 warm than on a cool day. In twenty-four 

 hours the veal tubes became turbid. They 

 were examined and Gyrococcus was found to 

 be present in great numbers, together with a 

 few other forms. These were then isolated on 

 agar and after about forty-eight hours, small, 

 round or oblong, smooth, cretaceous colonies 

 were found, which showed again after micro- 

 scopic examination that our bacterium grows 

 on agar. Other sterile tubes were inoculated 

 with these pure colonies and after twenty- 

 four hours more a pure growth was obtained. 

 These tubes remained odorless from the be- 

 ginning of the growth to the time when the 

 nutriment became exhausted. The first im- 

 pure set of tubes had an odor due to the pres- 

 ence of septic forms. 



For inoculation purposes, the fact that 

 larvse looked healthy externally was not con- 

 sidered to be sufiicient evidence that they 

 were free from infection, for a larva may ap- 

 pear reasonably healthy and feed normally 

 with a greater or less number of germs in its 

 system. As a matter of fact, if the tempera- 

 ture and food conditions are favorable a larva 

 may pass through its sixth moult, pupate and 

 even transform into a moth, carrying a num- 

 ber of Gyrococci along during the process. 

 External conditions have a great influence on 

 the rapidity with which the Gyrococcus multi- 

 plies within its host and for that matter 

 within the veal tubes also. Hence, owing to 

 the apparent feeble virulence which the Gyro- 

 coccus has when few in numbers, the external 

 appearance of a larva means absolutely noth- 

 ing. The blood, however, affords a very ex- 

 cellent diagnostic medium. The caterpillars 

 were therefore tapped and only those were 

 used in the experiments which were found to 

 be free from the Gyrococcus. The blood was 

 usually tapped from one of the prolegs. This 



operation can be repeated on the same larva 

 at intervals of a day or two without injuring 

 it. After tapping the blood each caterpillar 

 was isolated in a separate, clean box and fed 

 only with food which had been carefully se- 

 lected and washed. 



All the caterpillars which were pronounced 

 free from infection after the blood had been 

 carefully examined for Gyrococcus were di- 

 vided into four lots. Each lot was used for 

 an experiment with a pure culture of the bac- 

 terium. Twelve caterpillars were inoculated 

 in the proleg and twelve in the dorsal vessel. 

 Four controls accompanied each one of these 

 lots. Twelve caterpillars were fed with the 

 pure culture from a sterile pipette and four- 

 teen were fed with leaves smeared with the 

 culture. 



The table given below comprises the results 

 of one series of our experiments. The rate of 

 death at each day succeeding the inoculation 

 or the feeding is represented. Since at this 

 time all of the caterpillars were full grown 

 several of them pupated. 



TABLE 



The first and second days were very hot. 

 The third and fourth days were very cool. 



Number of Days After 

 iDoculatioQ or Feeding 



First day . . . , 

 Second day. . 

 Third day . . . 

 Fourth day . . 

 Fifth day . . . 

 Sixth day . . . 

 Seventh day . 

 Eighth day . . 

 Ninth day . . . 

 Tenth day . . . 

 Eleventh day 



No- of Caterpillars which Died 



It will be seen from the table that ten cater- 

 pillars out of the twelve inoculated in the 

 proleg succumbed to the disease. Two out of 

 the ten died in the pupal stage. Of the sur- 

 viving two, one is still a pupa at the time of 

 writing and one emerged. Ten out of the 



