VIIL] BACTERIUM. C5 



organism is present in large numbers in the blood and organs of 

 fowls dead of this malady, which is chiefly characterised by the 

 following symptoms : The animals are somnolent, weak in 

 their legs and wings, and they die under symptoms of extreme 

 sopor. On post-mortem examination, haemorrhage is found 

 in the duodenum. The smallest quantity of the blood is 

 infective. Pasteur successfully cultivated the bacteria in 

 neutral chicken broth, at 25 to 35 C., and with it inoculated 

 the fatal disease. The organism is probably a bacterium termo, 

 very minute and slightly constricted in the middle, so that it 

 appears of the shape of an 8. When cultures of this bac- 

 terium l are kept for some time (one, two, three or more 

 months), their virulence becomes diminished or attenuated 

 (owing, according to Pasteur, to the action of oxygen), and 

 this diminution of virulence is in direct proportion to the 

 time the culture is kept. The diminution or attenuation 

 shows itself in this that according to the length of time the 

 culture is kept, the number of animals killed by its inocula- 

 tion gradually diminishes, and it ultimately ceases to kill at 

 all. Each culture of diminished virulence transmits its 

 attenuation to the next following culture (?). It is possible 

 to obtain cultures of such a low degree of virulence that 

 when inoculated into the skin of a fowl only a local effect is 

 produced, a peculiar infiltration ; but the animal survives, 

 and is then protected or " vaccinated " against the more viru- 

 lent material. But in order to produce this protection, it "is 

 necessary that the culture (vaccine) should be of the proper 

 strength. If it does not produce a local effect it gives no 

 protection. 



In fresh cultures the bacterium is more in the shape of a 

 rod, constricted in the middle ; in cultures several days old it 

 looks very much more like a dumb-bell of micrococcus (see 

 note on previous page). 



Babes' 2 has found the bacteria in the tissues and blood- 

 vessels of animals dead of the disease, both inoculated and 

 epizootic, in the shape of rods of about 0*0015 to 0*002 mm. 

 in length and about 0*00025 mm. in thickness ; the ends 

 always staining more deeply than the middle part. 



but had the bacterium of fowl-cholera and an accidental micrococcus together. 

 The latter would predominate as time passed on, so that after a few days it 

 would far outnumber the bacterium ; and this is exactly what Pasteur's de- 

 scription suggests. He says that at first the microbe is rod-shaped, and after a. 

 few days it becomes a dumb-bell of micrococcus. The gradual attenuation by 

 time of the virulence of Pasteur's cultures of the microbe of fowl-cholera may 

 be due to the presence of this contaminating micrococcus. 



1 Trans, of the International Med. Congrett in London, 1881, vol. i. p. 87. 



Archives de Physiologic, July 1883, p. 49. 



P 



