1. A histological study was carried out in the buffalo on 176 gravid and 10 non-gravid uteri, representing the various months of pregnancy. Measurements of the different layers of the uterine wall as well as the diameter of the uterine glands and the height of their lining epithelium were made on both gravid and non-gravid horns.
2. The uterine wall shows a marked decrease in the thickness of the different layers as well as the total thickness with the advance of gestation. At the second month the gravid horn is 7.85 mm. in thickness, while by the tenth month it becomes 2.46 mm. The non-gravid horn decreases from 7.39 mm. at the second month to 3.27 mm. by the tenth month.
3. The lamina epithelialis in the gravid horn becomes desquamated in the first three months of pregnancy and restores itself in horns containing foeti of 15 cm CVR length or more, i. e. at the beginning of the fourth month. Oedema of the endometrium is first noticed at the fourth month and disappears at the seventh month.
4. The diameter of the superficial as well as the basal uterine glands in both the gravid and the non-gravid horns increases to a maximum at the ninth month. In general the superficial glands possessed higher epithelium than the basal glands, and the glands in the gravid horn had higher epithelium than in the non-gravid.