st the disease?

_3dly._ Amongst the animals attacked by the disease, how many recover,
and under what circumstances? How many succumb?

_4thly._ Are there any animals of the ox species decidedly free from any
susceptibility of being affected from the contagion of pleuro-pneumonia?

_5thly._ Do the animals, which have been once affected by a mild form of
the disease, enjoy immunity from subsequent attacks?

_6thly._ Do the animals, which have once been affected by the disease in
its active form, enjoy such immunity?

To determine these questions, the commission submitted at different
times to the influence of cohabitation with diseased animals forty-six
perfectly healthy ones, chosen from districts in which they had never
been exposed to a similar influence.

Of these forty-six animals, twenty were experimented on at Pomeraye, two
at Charentonneau, thirteen at Alfort, and eleven, in the fourth
experiment, at Charentonneau.

Of this number, twenty-one animals resisted the disease when first
submitted to the influence of cohabitation, ten suffered slightly, and
fifteen took the disease. Of the fifteen affected, four died, and eleven
recovered. Consequently, the animals which apparently escaped the
disease at the first trial amounted to 45.65 per cent., and those
affected to 21.73 per cent. Of these, 23.91 per cent. recovered, and
8.69 per cent. died. But the external appearances in some instances
proved deceptive, and six of the eleven animals of the last experiment,
which were regarded as having escaped free, were found, on being
destroyed, to bear distinct evidence of having been affected. This,
therefore, modifies the foregoing calculations, and the numbers should
stand thus:--

15 enjoy immunity, or 32.61 per cent.
10 indisposed, " 21.73 "
17 animals cured, " 36.95 "
4 dead, " 8.98 "

Of the forty-two animals which were exposed in the first experiments at
Pomeraye and Charentonneau, and which escaped either without becoming
affected, or recovering, eighteen were submitted to a second trial; and
of these eighteen animals, five had, in the first experiment, suffered
from the disease and had recovered; five had now become affected; and
four had been indisposed. The four animals submitted to the influence
of contagion a third time, had been affected on the occasion of the
first trial. None of the eighteen animals contracted the disease during
these renewed exposures to the