1. In the experiments here presented, P. avicida proved incapable of inciting fowl cholera when introduced directly into the alimentary tract. On the other hand, when administered into the upper respiratory passages, it induced typical disease.
2. When P. avicida was introduced into the nasal passages of controlled, selected chickens, some died of typical septicemic cholera, a few developed chronic pneumonias and other conditions and succumbed, a few developed localized upper respiratory inflammations, such as rhinitis, roup, and wattle involvement, while yet a few others became "healthy" nasal carriers. Usually, however, more than 50 per cent resisted infection. Repeated titrations of this sort gave, in general, uniform results, save that in spring and summer the per cent mortality decreased.
3. P. avicida was recovered from a number of cases of "spontaneous" roup, rhinitis, and wattle disease.
4. Groups of chickens reacted similarly to doses of virulent P. avicida varying from 20,000,000 to 20,000. Outside these limits, dosage exercised a marked influence on mortality.