94 MICRO-ORGANISMS AND DISEASE. [CHAP. 



through successive animals, as was maintained by Coze and 

 Feltz. 1 



(c) Bacterium of fowl-cholera (microbe du cholera des poules]. 

 Semmer, Toussaint, and Pasteur 2 have shown that this 

 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, haemor- 

 rhage 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 bacterium 3 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 pro- 

 portion to the time the culture is kept. The diminution or 



1 Strasburg, 1866 ; Paris, 1872. 



2 I place this here as a bacterium, but it is not quite decided, and not 

 quite clear from Pasteur's description, whether the microbe is only a 

 micrococcus dumb-bell, or a bacterium termo. Compare also Semmer 

 (Vergleichende Pathologie, 1878), Perroncito (Archiv f. wiss. u. pract. 

 Thierheilk. 1879. Toussaint (Comptes Rendus, xci. p. 301) considers 

 the disease identical with Davaine's septicaemia. I am inclined to think 

 that Pasteur has not used pure cultivations, but had the bacterium of 

 fowl-cholera and an accidental micrococcus together. The latter would 

 predominate as time passes on, so that after some days it would far 

 outnumber the bacterium ; and this is exactly what Pasteur's description 

 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 atten- 

 uation 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. 



3 Trans, of the International Med. Congress in London, 1881, vol. i. 

 p. 87. 



