The following experiments were carried out in order to observe the influence of light and dark on mitoses of the hepatic cells. Normal white rats weighing approximately 150gm. were placed in light or dark for a certain duration, and were then bred in rooms with certain degrees of light and dark. Their hepatic cell mitoses were observed at specific time intervals. On the other hand, the sera of the white rats which had been left in light or dark for a certain duration were injected to normal white rats and their hepatic cell mitoses were observed at specific time intervals.
The following observation were made:
1) The number of the hepatic cell mitoses of the white rats placed in light decreases to the lowest level at first and then increases gradually to the normsl level, although there is a mild degree of differences depending upon the duration of exposed hours. Thus, the white rats left in light reveals a decrease in hepatic cell mitoses.
2) The number of the hepatic cell mitoses of the white rats kept in dark decreases at first to the lowest level and then increases gradually to the normal level, although there is a mild degree of differences depending upon the duration of exposed hours. Thus, the white rats left in dark reveals a decrease in hepatic cell mitoses.
3) The sera of the white rats kept in light for a specific length inhibit the hepatic cell mitoses of normal white rats at first; the number of mitoses then returns gradually to normal, although there is a mild degree of differences depending upon the time elapsed before the collection of the sera. The degree of inhibition is most pronounced in the sera collected at 24 hours and is least in the sera collected at 72 hours in a free state after being kept in light for 4 hours.
4) The sera of the white rats kept in dark for a specific length inhibit the hepatic cell mitoses of normal white rats at first; the number of mitoses returns gradually to normal, although there is a mild degree of differences depending upon the time elapsed before the collection of the sera. The degree of inhibition is most pronounced in the sera collected at 12 hours and is least in the sera collected at 72 hours in a free state after being kept in dark for 4 hours.
5) The sera of both series of white rats in light and in dark for 4 hours respectively, inhibit hepatic cell mitoses of normal white rats. However, when the rats are kept for one week in dark or light, ceases and the number of mitoses returns to normal.
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