Scientia Sinica

116 SCIENTIA SINICA Vol, V

development of the growing epidermis, parallel to the level of the wound. The same picture is found in the case of guinea pig (Plate V, fig. 1, A), indicating that the tip of the new pigment epidermis is growing from lower right to upper left. In front of the new epidermis the leucocytes are arranged in a single column along the direction of advancement of the epidermis (from A to B), while in the upper region the leucocytes in the scab still remain in the original longitudinal orientation (Plate V, fig. 1 C). In specimens of the later stage, when the new epidermis has reached the cartilage, the leucocytes penetrate into the cartilage transversely along the direction of growth of the epidermis (Plate VI, figs. 3 and 4). It is plain that the direction of migration of leucocytes coincides with that of the advancement of the epidermis.

The second change of leucocytes in the wound is disintegration of cells. On the anterior and the inner sides of the new epidermis, there are deeply stained fragments of nuclei of leucocytes (Plate IV, fig. 4, in the marked rectangle). Among these nuclear fragments of leucocytes, some are solitary spheres surrounded with a layer of clear substance (Plate IV, fig. 4, A), resembling the clear cells; and some are aggregates of formless masses (same figure, B). At the same time, among the newly formed epidermal cells, there are fragments of nuclear substances (same figure, C), growing with the advancement of the new epidermis. This condition shifts forwards, and can only be observed in the region where the new epidermis has just formed. After the epidermis heals, their appearance is markly reduced or completely absent (Plate VI, fig. 2). This suggests that the leucocyte nuclei participate in the new formation of epidermis. : Te

When these changes occur in the leucocyte nuclei, the specific granules of the leucocytes and the fragments of the nuclear substance mix together at the same time. Figure 2 of Plate I is a higher magnification of the rectangular area of fig. 2 of Plate V. This area is selected to indicate the anterior end of the growing epidermis which advances along the direction as indicated by the arrow point, A, in the latter figure. Under higher magnification the disintegrating leucocytes (which can be judged from the stainable red granules that they are the morphological modification of leucocytes), are in forms of granules, chains, and rods, which are mixtures of nuclei and special granules. Among the disintegrating leucocytes, there are lightly stained. newly formed’ young cells of different sizes and shapes (Plate I, fig. 2, AB). This again shows that after the disintegration of the leucocytes, their specific granules and nuclei mix together to participate in the formation of the new epidermis.

(3) Changes of the collagenous fibres in front of the newly formed epidermis. With Mallory’s staining the collagenous fibres are coloured blue and can be distinguished from other tissues. Figure 1 of Plate I, and figure 2 of Plate IV, show the early changes of the collagenous fibres having been described above. In fig. 3 of plate II, the disintegration of collagenous fibres can be clearly shown. In this figure the upper right 1s the scab, under which