Scientia Sinica

No. 1 MA: FORMATION OF NEW EPIDERMAL’ CELLS DURING WOUND-HEALING 127

they are able to divide mitotically. Occassionally we find larger cells on the specimen showing mitotic division (Plate VII, fig. 3, A), which probably represents that young cells are in the process of changing into normal epidermal cells through mitosis.

According to the theory of V. N. Michin™!, cells mutiply not only by means of mitosis, amitosis, and budding, but also from a large amount of nuclear substance released from cells, and new cells are developed therefrom.

E. E. Malovitchko and T. N. Rupasoya in studying wound-healing have discovered that the living substance released. from leucocytes (pus) is the source of newly formed cells. They described the process of formation and said: “Nuclei are formed by condensation of the fragments resulting from the segmentation and the breaking down of the nuclei of the neutrophil leucocytes. Probably this is not a degenerative process, but a special type of mitosis. These fragments gather into a deep-stained spherical body resembling the nucleus of a lymphocyte. It is then isolated from the destroyed neutrophil leucocyte and becomes the central part, surrounding which accumulate small cytoplasmic granules from the decomposing products of the cytoplasm of the neutrophil.”

Our results agree with the statement made by the above mentioned Soviet workers.

From the aforesaid experiment naturally arise two other questions: Does the development of tissues follow a certain rule? What role does the living substance play in cell production of normal organism?

1. During the process of wound-healing there is a certain rule observed from the development of the living substance into different kinds of tissues.

For example, when the living substance develops into epidermal cells, it is not that the cells grow diffusely from anywhere on the surface of the wound at random, but that they always develop gradually along the margins of the epidermis of the wound or on the cut surfaces of the hair follicles and sweat glands. The direction of growth of the new epidermis is toward the centre of _the wound from the two sides.

There is another example. After the wound heals and the epidermis reaches a certain thickness, the development of the disintegrating tissues directs chiefly not to the formation of epidermis, but to the development of other tissues. On the specimen taken 144 hours after a wound was made (Plate Ill, fig. 2), the epidermis has grown to a considerable thickness, and under the new epidermis at A in this figure there is one kind of mesenchymalike tissue consisting of young cell nuclei and branched advantitious cells. At the same time there are collageous fibres between them. This specimen js fixed with Susa and stained with Mallory’s the collageous fibres taking the blue colour. This picture shows that the development has turned to the connective tissues. In the lower region the cartilageous tissue is still in the process

—= ae