340 
M. L. PASTEUR. 
As we are aware, it is a terrible and rapidly fatal affection, 
specially by the direct inoculation of its microbe. It then be¬ 
comes remarkable that at times it assumes a chronic character ; 
indeed, in some cases, hens are seen which, having been inocu¬ 
lated, after being very sick, do not die, and recover a relative 
degree of health. Still, they eat little, become aedemic, as proved 
by the discoloration of their combs; become more and more lean 
and finally die, after weeks or months of languor. This fact 
would have been of secondary importance, if in those peculiar 
circumstances, the microbe was not most generally found in the 
body at the time of death, proving conclusively that the parasite 
had been preserved in the animal from the period of the last 
inoculation, always present and active, though acting quietly and 
unobtrusively, and surely, though slowly. It destroying its vic¬ 
tim, no doubt, remains lodged in some vaccinated region, which 
becomes unfavorable, by those conditions, to an easy culture. 
Vaccinated hens principally present this form of disease, which, 
in truth, however, is not of frequent occurrence. One might 
suppose that, in these conditions, there would be transformation 
of virulent into attenuated lymph, but this would be an error. In 
those cases, the virulency of the microbe is, on the contrary, very 
great, as can be seen by taking the blood of the hen killed by way 
of cultures and inoculating it to fresh birds. 
Such facts will help us to understand the possibility of those 
long incubations of virus (that of hydrophobia, for example) which 
after remaining in the body, in a partially latent state, manifest 
their presence suddenly, at length, by the most manifest virulency 
or death. 
Will they not also enlighten human pathology ? Alas! do we 
not often see diseases of the order of virulent affections, such as 
measles, scarlet fever, and typhoid fever, taking on the most seri¬ 
ous results, protracted, disastrous, and often incurable ? The 
circumstances I have mentioned are of the same nature, but here 
we can see their true cause. 1 conclude by noticing another 
peculiarity no less interesting to scientific men. 
In very well vaccinated and very healthy hens, an abscess 
sometimes appear, on some parts of the body, full of pus, but 
