Scientia Sinica

114 SCIENTIA SINICA Vol, V

material. Owing to the extreme thinness of its epidermis, usually of two to four layers of cells, it may be easy to find out any change to take place. The wound was produced by cutting off one stripe of tissue near the margin of the rabbit’s ear; or a difinite area of skin was removed from the back with the subcutis remaining intact. No aseptic precaution was taken with the wounds, yet during the process of healing there has not been observed any sign of inflammation of pyogenic nature. The same experiment was also carried out on the guinea pig’s ear.

Five cc of 1% aqueous solution of a vital dye, trypan blue, had been injected intravenously into some of the rabbits once the other day, for 5 times, before the wound was made. Under living conditions’ a large amount of the dye was taken up by the macrophages. Any change observed on the preparation made from these animals should have taken place while the animals were alive, and it is not due to any technical artefacts.

A series of successive observations was made with specimens from rabbits’ ears, once per hour within 24 hours after wounds were made, and afterwards, every 4 hours, until the wounds healed (completed about 5 or 6 days). Further specimens were taken once every 12 hours until 180 hours when the subcutaneous tissues and cartilage were completely healed. Specimens were taken from 5 or 6 animals at every time interval.

Different fixatives, as formalin, Susa, Zenker-formalin, etc. were used for fixing the specimens taken from every stage. For differentiation of different tissue elements, different staining processes were employed: orcein for elastic fibres, Mallory’s for collagenous fibres and matrix of cartilage, hematoxylineosin for tissue structures in general, Heidenhain’s iron hematoxylin for nucleus and nucleolus. Specimens having been injected with trypan blue were fixed with Susa; they were stained with 0.25% acid fuchsin for 14 to 2 hours, and then counterstained with saturated aqueous solution of picric acid. Thereby, the tissues and cells taking trypan blue came out with clear contrast.

Specimens examined were made in serial sections of 5-micron in thickness. Sections were made in two kinds of planes both perpendicular to that of the wound. One series is perpendicular to the cartilage plate, while the other is parallel to it. Some of the sections from the latter go through the whole cartilage plate, hence a complete view of the changes taking place in the cartilageous tissue.

OBSERVATIONS The results of observations are described as follows:

I. The process of scab formation.

The scab is already formed within 13 hours after the wound was made on the rabbit’s ear (Plate I, fig. 1). On this specimen two parts can be dis-