In Vitro Experiments on the Effects of Mouse Sarcomas 180

INThODUCTION Previous experiments have given evidence that mouse Sarcomas 37 and 180 produce an agent which promotes the growth of spinal ganglia (1) and of sympathetic ganglia (l@) in the chick embryo. This effect was first observed in experi ments in which small pieces of tumor were im planted in the body wall of 3-day embryos, where they grew vigorously. Later, the same effects were obtained when the tumors were transplanted ex tra-embryonically to the allantoic membrane of 4-day embryos (10, 11, 13). The latter result was considered as conclusive evidence that we are dealing with a diffusible agent. The response of the nervous system was found to be selective and complex. Only the sensory and paraand prevertebral sympathetic ganglia showed a reaction, whereas all centers in the spi nal cord were refractory. The hyperplasia of the ganglia was due partly to an increase in cell num ber and partly to a cellular hypertrophy. The differentiation of nerve fibers was accelerated, and their number was increased to an extraordinary degree. The supernumerary fibers emerging from the hyperplastic ganglia flooded the adjacent viscera: mesoand metanephros, gonads, spleen, adrenal, thyroid, parathyroid glands, and also the tumor, in cases of intra-embryonic transpianta tions. Normally, these organs receive only a very scant nerve supply or none at all, in corresponding