Abstract
The well recognized syndrome of pulmonary suppuration in the albino rat is, as in many human affections, an advanced stage of the condition. The earlier manifestations of the disease are imperfectly understood and the common appellation “pneumonia” for the well developed lesion is a reflection of this lack of knowledge of the fundamental nature of the process. The lesions of the lungs vary greatly according to the stage and extent of the process but the essential nature of the completely developed disease is that of chronic lung abscesses.
We have been particularly impressed with the frequent occurrence of atelectasis in white rats which are apparently in perfect health. These observations lead us to suggest that atelectasis subsequent to bronchial obstruction is a primary factor in the development of pulmonary infection in the white rat. To substantiate this hypothesis it is necessary to show that obstructive atelectasis occurs in white rats showing no evidence of pulmonary infection and that organisms may gain an entrance to the lungs and selectively localize in the collapsed lobes. The probable pathway of infection has been indicated by Jones, 1 who isolated organisms occurring in the environmental atmosphere, from the lungs of several laboratory animals. The regularity with which the cultures were positive varied directly with the amount of dust in the atmosphere. It is a well known fact that after bacteria have once gained entrance into the body their ability to proliferate and invade the host is greatly increased by an obstruction to the part.
Our own observations have clearly shown that an obstructive atelectasis is a very common finding in white rats. This condition has been observed many times in animals showing no gross or microscopic evidence of pulmonary infection. The atelectatic areas vary in size from a minute portion at the tip of a lobe to a massive collapse of the entire right side and the infra-cardiac lobe.
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