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Article
December 14, 1901

ON THE EXISTENCE OF PATHOGENIC AGENTS TOO SMALL TO BE SEEN.

JAMA. 1901;XXXVII(24):1610-1611. doi:10.1001/jama.1901.02470500038004
Abstract

Studying a destructive epidemic disease among chickens, Lode and Gruber1 of Innsbruck made the observation, which was confirmed by frequent repetition, that the specific cause, whatever its nature may be, passes through Berkefeld or Chamberland filters. Filters of this kind, it is well known, keep back all bacteria that are visible with our present means of magnifying microscopic organisms. A few years ago Loeffler and Frosh showed that the virus of foot and mouth disease also passes through such filters, the filtrates being virulent. Recently Beijerinck has demonstrated that the cause of a disease that produces spots on tobacco leaves is a contagium that passes through porcelain filters. In these interesting cases two possibilities have been considered: Either the apparently sterile filtrate contains in solution an unusually active poison or the unknown agent is so small that it passes through the pores of a filter that retains the smallest

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