insusceptibility

Thus animals may prove refractory to a small dose of the poison of anthrax, yet Chauveau has shown that this virus will overcome all native or acquired insusceptibility when administered in excess.

Sometimes only one or two solitary cases of the affection are observed; at other times the disease becomes moderately prevalent, but a lack of virulence in the poison or a previously acquired insusceptibility of the individual protects the great majority of the animals exposed, while at others, still, the poison attacks nearly all exposed to its contagion.

Some individuals are refractory to vaccination, but complete insusceptibility is exceedingly rare.

It may well be suspected that the relative insusceptibility of chickens is in part due to the large amount of animal food consumed by them, and that the chilling process increases the receptivity by deranging sanguinification and nutrition.

The insusceptibility to anthrax is often characteristic of certain individuals or families or of the animals living in a particular district.