Observations on the Effects of Insulin Introduced Into the Medium of Tissue Cultures

A summary of the effects on the growth of tissue in vitro noted when insulin had been added to the culture medium is presented because of its potential value in this line of investigation. Dr. Thalhimer suggested the addition of insulin as a possible means to augment the growth of tissue and to disclose the nature of its action. Chick fibroblasts were cultivated from 9 to 10 day old embryos, the Carrel flask method being used. The medium contained glucose in percentages from 0.1 to2.5. Two sets of cultures were maintained. To one set, from 1 to 2 per cent. of insulin was added; to the second, otherwise identical, no insulin was added. The sugar content was determined in duplicate cultures by the Folin-Wu method, and the H-ion concentration was estimated by the drop calorimetric procedure. The perimeter of the growth was compared by using the planimeter method of Carrel