Specifically, a virus or bug passed to a pig is considered a huge threat in the medical community, because pigs can pass their diseases onto humans.
But by a process of successive and continued artificial cultures under different conditions, the virus of the organism is found to become attenuated; and when this weakened virus is administered, the animal is rendered immune against further attacks.
The next step was to endeavour so to modify and weaken the virus as to enable it to be used as a preventive or as an antitoxin.
Would the inoculation of the attenuated virus have a remedial effect on an animal already bitten ?
The exciting cause of the hypertrophy, in the case of the typical galls, appears to be a minute quantity of some irritating fluid, or virus, secreted by the female insect, and deposited with her egg in the puncture made by her ovipositor in the cortical or foliaceous parts of plants.