Ninety-five adult male rabbits were used in this experiment. Except 18 controlanimals, the rest, with a segment of radius sawed off under surgical operation, weredivided into different experimental groups. They were sacrificed at different time inter-vals and their parathyroid glands were dissected out immediately and processed accor-ding routine histological and histochemical methods. Three days after bone-fracture the parenchyma cells increased in size and in numberof vacuoles in the cytoplasm. The intensity of the ninhydrin-Schiff reaction and reactionof the alpha-acylamino carboxyl groups of proteins also increased. These changes in-tensified on the 7th day and did not recover to normal on the 35th day after opera-tion. On the 7th day the parenchyma cells also showed an increase of ribonucleic acid, adecrease in glycogen content, a rise in the activity of the enzymes: nonspecific esterase,acid phosphatase, and succinic dehydrogenase; and the capillary endothelium showed anelevation of alkaline phosphatase. On the 17th day the activity of esterase and succinic dehydrogenase subsided to nor-mal and on the 21st day the glycogen content and alkaline phosphatase activity returnedto normal. The above changes are correlated with the different stages of the bone healing pro-cess and their significance in parathyroid gland activity is discussed.

Thymus, lymph node and intestine (two pieces each) were taken from 20 adult guinea pigs and 10 adult rats. One piece was frozen in liquid nitrogen (-70℃) and cryostat sections were stained with Janszen and Nugteren (1971) method to demonstrate prostaglandin synthetase activity, Another piece was fixed in methanol, and paraffin sections were stained with HE and toluidin blue to demonstrate mast cell. Teased preparation of mesentery were stained by the same methods to show enzyme activity. Indomethacin inhibiting test was used as control. It is proven that the brown deposit represented the prostaglandin synthetase activity. These deposit existed in cytoplasm of mast cell, while and was absent in nucleus and specific granules. Prostaglandin synthetase positive mast cells distributed widely in lamina propria, axis of villi and submucosal layer in intestine, capsule, septa and medulla in thymus; capsule, trabecullum and paracortical zone of lymph node.