This case is reported because it includes not only the ordinary clinical observations, but also direct manometric blood-pressure and intratracheal respiratory pressure tracings, together with autopsy findings with histological report, all on a dog which had a widely patent ductus arteriosus Botalli with aneurysm of the duct itself and the beginning systemic and pulmonary aortæ. A further favorable condition was that death in this case was caused by rapid suffocation. By this means the physiological and pathological conditions or changes caused by the persistent patency of the ductus were all preserved unobscured by any other over shadowing diseased condition as is usual at autopsy.
From a study of the case from these different points of view, it seems that the clinical symptoms and abnormalities in blood-pressure and respiration. and the changes found in the various organs, which were associated with the persistent ductus, are all related, and