Autopsies on all the guinea-pigs kept for as long as 20 months failed to reveal any trace of tuberculosis, although the grass grazed by the animals was proved by subcutaneous inoculation to bear virulent organisms, which might have been expected to reach the alimentary tract in considerable numbers, at least in the earlier experiments.

By repeated infection of a grazing area it has been possible to induce tuberculosis in guinea-pigs grazed in the open and in those fed indoors on cut grass. In the 1932 experiment a total of thirty guinea-pigs were allowed access to plots of grass which had been infected, one, four and eight days previously and all failed to become infected. The combined experiments (1932 and 1933) suggest that under some weather conditions, animals, although admitted to pasture within a very short time of its infection may escape infection with tuberculosis, but that repeated infection of pasture results in a high incidence of disease in animals grazing on it.