Scientia Sinica

No. 1 MA: FORMATION OF NEW EPIDERMAL .CELLS DURING WOUND-HEALING’ 123

loss of epidermis due to desquamation. And they have found migration of lymphocytes from dermis into epidermis and their convertion into epidermal cells.

These investigators, though hold a different concept from the former one, all agree that the new epidermal cells come from the cells in the dermis.

It is thus clear that as regards the formation of new epidermal cells, all the scientists mentioned about can not get rid of the traditional idea that “all cells come from the pre-existing cells”, no matter what kind of cells is regarded by them as the source of the new epidermal cells.

2. Further discussion on the aforesaid theories of the origin of newly formed epidermal cells.

(1) New epidermal cells do not come from the pre-existing epidermal cells by means of mitosis.

Many investigators have discovered in their experiments that it is impossible for the epidermal cells to compensate the loss of cells due to desquamation by means of mitotic division.

Thuringer'*! examined the human epidermis, finding that the number of mitosis is scanty, and their ratios to the total number of cells are: epidermis of the ear, 1:268,275; that of the thigh, 1:378,325; that of the scalp, 1:2,414.

Ortiz-Picon®4 could not find any sign of mitosis in the epidermis of mice.

Arey! made a slight cut on the epidermis of the fish and amphibians, It healed after 3 hours. No cell under mitotic division was found and, in addition, he said that it was impossible to heal the wound in 3 hours by means of mitotic divisions even there were any. He performed another experiment and reached the same conclusion.

Harabath! made larger wounds on the epidermis of fish. They healed in 12-36 hours. From the results of his observation, he concluded that mitotic figures could not be found in the epidermis as well as in the dermis.

Both Oppel!! and Holmes”! got layers of epidermis in tissue culture. They found no mitosis in the early stage of the growth of the tissue, but in later stages.

Voit! made further chemical analysis of the weight of the epidermal cells desquamating every year. The result shows that there are 116.14 grams of epidermal cells to desquamate every year from a square metre of epidermis not including those from hair follicles.

Now return to our experiment. We have found that the growth of new epidermis is rather rapid. Within five days after a wound was made the new