1. There is a great difference between embryonic and adult tissue as far as their growth outside of the organism is concerned. Adult tissue grows only in plasma. Embryonic tissue grows also very well in serum and serum plus agar. In Ringer's solution and in Ringer's solution plus agar no growth occurs, whether embryonic or adult tissue is employed; survival and emigration of cells are seen to some extent.
2. For the growth of connective tissue cells of chick embryo, unheated homogenic serum is a better culture medium than heated serum. The growth of epithelial cells is not thus influenced.
3. Heated heterogenic serum is a better culture medium for growth of embryonic connective tissue cells than unheated.
4. There is an inverse ratio between the hemolytic power of heterogenic sera and the extent of growth of tissue in them. This inverse ratio is not found in heterogenic plasmas.