Scientia Sinica

120 SCIENTIA SINICA Vol. V

mixes with the disintegrating substances of other tissues. Figure 5 of Plate III shows that the growth of new epidermis is very rapid—the young cell nuclei and the young cells are already formed before the cartilage is completely disintegrated, so that they fill in the lacunae of the cartilage.

When the new epidermis has reached a certain thickness, the disintegrating substances under the new epidermis cease to form epidermal cells and turn to the formation of connective tissue (Plate III, fig. 2). Under the new epidermis (A), fine bundles of blue collageous fibres are found intervening between the purple disintegrating substances, and later they develop into subcutaneous connective tissue.

(6) The process of the formation of new epidermal cells is summed up in the following sequence according to the time of stages of the specimens observed.

1. The disintegration of the tissues under the scab’ including all the damaged tissues, such as leucocytes, macrophages, etc.

2, The mixing up of the disintegrating tissues into formless masses. By appling different staining techniques, different tissues on the specimens show their specific colouration, and their mixture takes a more intense colour hue of different stains. Their colour depends on the stains used, and thus’ in fig. 1 of Plate I, it shows deep purple by Mallory’s staining method, and when acid fuchsin and picric acid are used as in the case of specimens injected with trypan blue, the disintegrating substances appear in different colours, as red, yellow, blue and brown. (Plate I, fig. 4).

2. There are complex chemical and structural changes taking place in the mixture of the disintegrating substances, and through these changes they develop into aggregates of different sizes, and further into young cell nuclei.

4. Young cells are formed by the development of cytoplasm in the periphery of the cell nuclei. They further develop into normal cells.

5. When these cells reach maturity, they multiple by ordinary mitotic divisions. Ordinarily mitosis can only be found among the well-formed new epidermal cells, and is absent in the growing region. -

Discussion

L Theories in relation to the origin of new epidermal cells.

(1) In the past, under the influence of the traditional concept that all cells can only come from pre-existing cells, almost all authors have, “with regard to the problem of the formation of new epidermal cells, accepted the saying that such new cells come from the pre-existing epidermal ones. Even up to now, it is so described still in all textbooks concerned. Take for examples,