Observations on the changes seen in living cells during growth and division

The observations recorded in this paper were made on cultures in vitro of embryonic and adult chick tissues. The cultures chiefly studied were choroidal cells from the eyes of seven to nine days’ chick embryos and cartilage cells from knee-joints of adult fowls. The method of cultivation was embedding small fragments of tissue on a coverslip in one drop of chick plasma, to which was added one drop of embryo chick extract. The coverslip was inverted over a hollow glass slide, sealed with melted paraffin wax, and at once placed in an incubator at 39° C. The tissues were sub-cultured every second day. The cells observed were found in cultures which had been growing for 24 hours in the incubator after sub-culture.