Abstract 1. 1. Granulation tissue (24 hours to 30 days old) from rats was examined with regard to the capacity of the tissue to combine with toluidine blue. It was found that the uptake of dyes increased from 2.0–3.0 γ per mg of tissue on the first day, to 7.0 γ per mg of tissue on the sixth to the ninth day, whereupon it decreased until the value for normal skin was reached on the 15th day. 2. 2. The variations in the capacity of taking up dye are probably to be attributed to extracellular mucopolysaccharides. The possibility that the results are due to other substances is considered. 3. 3. Fibroblast cultures were grown with the addition of water extracts from granulation tissue. An inhibiting effect was demonstrated, which reached a maximum with extracts from six to nine days old granulation tissue. Growth of tissue cultures with physiological salt extract from the granulation tissue showed that the extract from young tissue had a slightly growth-promoting effect. 4. 4. In conclusion the authors have tried to combine the results with the histologic picture of wound healing.