The growth of all the pathogenic bacteria studied was favorably influenced by the addition of small amounts of tissue extracts.

Beef heart, rabbit and cat tissues, and human nasal secretions contain substances favorable to the growth of the organisms tested. The mucosa of different organs, spleen, liver, and kidney, are relatively rich in these substances, while muscle is relatively poor. The favorable effect of the extracts is manifested by an enhancement of growth and a reduction of lag.

The water-soluble substances are apparently the ones essential for bacterial development; the ether extract has no effect on growth.

Experiments are reported which indicate that the substances in question belong to the class of so called vitamines.

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