A further report on yolk sac cultivation of tumor tissue.

About five years ago a technic was described by means of which rat and mouse tumors could be grown in the yolk sacs of embryonated eggs (5, 7). At that time, it was pointed out that by this method relatively large masses of pure cultures of rat and mouse tumor tissue were readily obtainable. Other laboratories have used the technic successfully (1, 2, 8). Since the publication of the initial reports, this manner of growing tumor tissue has been used continuously in this laboratory. Both rat and mouse tumors have been carried over a period of years by egg to egg inoculation. The present report is made with the object, first, of describing the yolk sac technic as modified by experience with several hundred thousand inoculations and, secondly, to report the discovery of a C3H mammary carcinoma which grows with unusual facility by this method of cultivation.