Abstract
The classic substratum for tissue cultures, developed by Harrison 1 Burrows, 2 and Carrel, 3 consists of chick plasma clotted with chick embryo juice and with an overlay of embryo juice variously diluted. Such a plasma clot without embryo juice overlay is insufficient to support prolonged tissue growth except when frequently renewed by transplanting the cultures to fresh substratum. It supplies an ill-defined but far from negligible level of nutritional factors. In any precise study of cell nutrition, these factors must either be clearly defined or, if possible, eliminated before the substratum can be satisfactorily evaluated as a base line. Various attempts have been made to arrive at such an evaluable base line. Porter and Hawn 4 have used clots prepared from purified fibrinogen coagulated with thrombin. Both these substances are more clearly defined and more nearly inert than are plasma and embryo juice, but they are still not completely defined. Evans and Earle 5 have been successful in developing a procedure for cultivation of tissue cultures on sheets of perforated cellophane, which is nutritionally fully inert. This is a very satisfactory solution of the nutritional problem, but such cellophane is not easily available to all workers throughout the world. Lewis, 6 White, 7 and others have grown cultures directly on glass. This is likewise a fully satisfactory solution of the nutritional problem but the results obtained are somewhat unreliable.
Fischer 8 has approached the problem from quite a different angle by seeking to eliminate the nutritional factors from the classic plasma clot. He showed that when chick plasma and embryo juice, after thorough dialysis against a dextrose-Ringer's solution, were used in the preparation of clots on which to cultivate chick fibroblasts, no growth whatever would occur thereon.
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