1. Fragments of breast muscle from a 12 day old chick embryo have been kept alive in single flasks for an entire year without being transferred. The nutrient materials were supplied by frequent applications of adult fowl serum diluted with Tyrode solution.

2. When fragments of fixed tissues are cultivated in serum, cell multiplication and cell death are both reduced to an extremely low level.

3. The presence of a plasma coagulum is not essential to the continued survival and further development of tissues cultivated inserum.

4. The fibrinogen, prothrombin, and fibrin of coagulated plasma are not essential to the development of connective tissue fibers in vitro.

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