[Effect of the time of the day when the lesion was produced on the course of mesothelial proliferation].

The course of mitotic activity in the rabbit mesothelium of parietal peritoneum was studied depending upon the daytime when the lesion was produced. In the first series of experiments (I) the operation was performed from 8 to 10 a. m., and in the second series (II) - from 8 to 10 P. M. After the operation the animals were sacrifieced: one animal every 3 h during 5 days. Mitotic activity was investigated along 13 mm from the edge of the wound in flat film preparations. The data obtained were statistically treated applying approximation of the process course by the method of weighed sliding averages. The first mesothelial mitoses appeared: in the first series (I) of experiments - in 24 h, in the second series (II) of experiments - 21 h. Further, proliferation of the mesothelium appeared in different parts of the tissue with various intencity and was of wavy character. Regardless of the time when the lesion was produced, mitotic activity was the greatest in the first zone, 4.8 mm wide its maximum 33 h after the operation. The character of the regenerative process in the mesothelium depends on the circadian phase of the organism at the time of the operation, that influences the time when mitotic activity begins, its quantitative indices, the area of the tissue involving into the reaction, expressiveness of the rhythmicity of the process. During 5 days, in the II series of experiments three waves were noted, and in the I series - five waves were noted and their periods were near the diurnal.