The long bones of the fore and hind limbs of 1-day and 5-day new born mice werefixed in Zenker's 10% neutral formalin and Carnoy's fixatives. They were sectionedwithout decalcification and stained in Mallory for general structure, in McLean & Bloom'smodification of Kossa for calcification and in periodic acid-Schiff's reagent for glycogenrespectively. It was found that in the humerus the length of the cartilaginous cell columns, thedegree of calcification in the cartilaginous matrix and the extension of the subperiostealcollar in the cartilaginous level were all more extensive in the proximal end than that of thedistal. The situation was the opposite in the case of femurus. The development in theproximal ends of the radius and ulna were less extensive than the distal. On the otherhand, the proximal ends of the tibia and fibula were more extensive than the distal. Hence,the increase in length of the fore limb would be mainly in the shoulder and wrist jointswhile that of the hind limb in the knee joint. The distribution of glycogen in the chondrocytes was found to be more abundantin the transitional zone between the flattened and hypertrophied cell columns. Thesignificance of this distribution in relation to phophatases, nutrition and calcification wasdiscussed.

Experimental myocardial lesions were produced in 79 adult rats by the application of electrocoagulator.The animals were killed at intervals from 12 hours to 60 days after the injury and the lesions were studied histologically and histochemically. Three stages can be distinguished during the process of wound-healing in the cardiac muscles. The first stage,12 hours to 2 days after injury.The retrogressive changes of in- flammation were apparent.Degeneration and necrosis of heart muscles were present in the area of the injury.Young connective tissue were formed. The second stage,4 to 13 days after injury.The newly formed cardiac muscle fibers retroceded.The scar was formed of ripe connective tissue. After injury,the change in glycogen content in the cardiac muscle fibers was more conspicuous of than that of the desoxyribose nucleic acid.

The hearts of the 49 adult male rats were injured by the application of electro-coagulator, and the animals were killed at intervals from 12 hours to 2 months after injury.Another 8 rats were used for control. The regenerative changes during the process ofwound-healing were studied with histological method. Two to twenty days after injury, the regenerative changes in myocardial fibers wereevident. The modes of regeneration were shown on several ways. (1) Two days after injury, at the border of the lesion, the terminations of somesurviving myocardial fibers showed variable degrees of dedifferentiation, the nuclei swelledup and the nucleoli increased in number and volume. Many of the nuclei were arrangedin pairs, especially in the papillary muscles. (2) Two to twenty days after injury, some mitotic figures were found in myo-cardial fibers. (3) Five to nine days after injury, there were many myoblasts in the center ofthe lesion along the necrotic fibers. For lack of favorable conditions, the myoblasts and the terminations of the survivingfibers could not continue to develope and differentiate. The lesion was repaired by thecicatrization.