Scientia Sinica

No. 1 MA: FORMATION OF NEW EPIDERMAL CELLS DURING WOUND-HEALING 117

the new epidermis grows from lower right towards upper left. Along its course of growth many blue-coloured collagenous fibres pass through it, from the normal tissue into the scab. The parts of collagenous fibres, where the new growing epidermis passes through, show disintegration and fragmentation, while the parts above and below the epidermis still remain morphologically intact. In the region, where the collagenous fibres disintegrate, one may find the fragmentation of leucocytes and the mixing of the red and bluecoloured substances. This indicates the mixing together of the fragments of collagenous fibres and leucocytes. Besides, along ‘the course of advancing epidermis there are immature cells which are erined faintly and have not yet acquired the distinctive form and shape (same figure, B).

In the H. E. stained specimens the mixing of the disintegrated collagenous fibres and leucocytes is not clearly shown, but on the better stained slides, as shown in fig. 4, Plate II, it is ready to observe. In the region where the photomicrograph was taken, the new epidermis has grown to considerable thickness. The direction of growth is from left to right. The scab is on the upper part, and under the scab on the right there are few new epidermal cells. The disintegrated collagenous fibres still can be identified in the newly formed epidermis (Plate I, fig. 4, A). Near the same place one may find the mixing together of the disintegrating leucocyte nuclei and fragments of collagenous fibres (same figure, B), and in its vicinity there is a deeply stained young cell nucleus still not acquiring a fully developed cytoplasm and a cell membrane (same figure, C). Moreover, there are also cases wherein a large, round-shaped foment of fremeemed nucleus of a leucocyte would with the development of cytoplasm resemble the form of a lymphocyte (same figure D), and when the nucleus is well formed, the surrounding cytoplasm

would become distinct (same figure, E). With the advancement of the grow-

ing epidermis, the immature cell nuclei are situated in the growing tip or along its margin, while cells with cytoplasm lie behind the tip. This indicates that the nucleus is formed first, and followed by the formation of cytoplasm and cell membrane. After the appearance of cytoplasm and cell _ membrane, it is then called a young cell.

The mixed debris from disintegrated collagenous fibres and leucocytes may develop into aggregates of different forms; some are larger and some smaller. The larger ones are shown in fig. 1, Plate II. In the same figure there are light-coloured swelling bodies formed of the aggregates and growing from right to left (as indicated by the arrow). Around the tip of its growth there are deep purple disintegrating tissues, composed of the fragments of collagenous fibres and leucocytes. Among the swelling bodies formed of the deep purple disintegrating tissues and light-stained aggregates, there are also deepstained aggregates (Pl ate II, fg. 1, A). This again can be observed in the lightly: nec swelling bodies Cae figure, B). The different shades of colour taken by the aggregates depend on the amount of disintegrating sub-