XIII ATTENUATION OF VIRUS OF FOWL ENTERITIS 113 



of the rabbit might have lost some of their virulence, 

 since the body of this animal is evidently not a favour- 

 able medium for their growth and multiplication. On 

 testing by experiment this supposition, it did not prove 

 correct. Twelve fowls were inoculated with broth 

 sub-cultures of the bacillus derived from the rabbit. 

 The result was this — that all twelve birds had 

 diarrhoea on the 5th or 6th day, and that nine died 

 (between the 7th and 9th day) and only three ^ sur- 

 vived. A broth sub-culture derived from the rabbit 

 proved, therefore, of a considerable degree of virulence, 

 worse than useless for protective inoculation, since 

 75 per cent of the animals inoculated died. 



Another set of experiments was this : a fowl had 

 died of fowl enteritis, after inoculation with culture, on 

 the loth day, that is later than usual, and I surmised 

 that possibly the bacilli in this fowl might be of an 

 attenuated virulence. From gelatine cultures of the 

 heart's blood of this fowl broth sub-cultures were then 

 made and after 24 hours' incubation at 'i^^* C. were 

 used for the inoculation of twelve fowls. Seven of 

 these died of typical fowl enteritis, the other five,- 

 though ill between the 5th and 9th day, survived. 



1 These three fowls were mentioned above as having been after- 

 wards used for a second inoculation with virulent material and proved 

 refractory. 



2 These five fowls were mentioned above as having been used for 

 a second inoculation with virulent material and proved refractory. 



I 



