STUDIES ON ENDOTHELIAL REACTIONS : II. THE ENDOTHELIAL CELL IN EXPERIMENTAL TUBERCULOSIS.

1. The epithelioid cell is of definitely endothelial origin. 2. The only reliable means of identifying and tracing this cell is, at the present time, a colloidal suspension of carbon, injected intravenously. Benzidine dyes will not accomplish this if used alone. 3. There is little evidence that the local tissue elements take an active part in the process of tubercle formation, until after the lesion is formed; the reaction is, in a sense, exudative, since the lesion is produced from cells which migrate to the site of inflammation. 4. The lymphocyte appears late and is not to be considered as a potential epithelioid cell; its presence in the tubercles is as yet unexplained.