Abstract
A series of 7 hypophysectomized rats and their litter mate controls was treated for various periods with daily injections (usually 20) of the growth-promoting hormone of the pituitary body. The experimental animals were operated upon at the age of 45 to 64 days. The rate of eruption of the incisors of these animals was measured for varying lengths of time preceding, during, and after replacement therapy (Table I).
A horizontal marking with a fine file (Swiss jeweler's screw head file) was made near the gingival line along the disto-labial margin of the upper incisor. With an adjustable caliper provided with fine points the distance was measured between the point where the marking crossed the disto-labial margin and the point where the surface of the gingivae crossed the same margin. This distance was read in twentieths of a millimeter with the aid of a stage micrometer and a dissecting microscope. The distance between the same points mentioned above was read 7 days later. The difference between the 2 readings represented the rate of eruption for that period. New marks had to be made each week in the normally erupting teeth. Operated and control animals received the same preparation† subcutaneously once daily in a dose proportional to the body-weight.
To obtain some idea of the accuracy of the individual measurements, 8 experiments on teeth of different lengths were performed. Each experiment was made up of 4 measurements on the same tooth. The standard deviations calculated for these experiments were found to have the following values expressed as percentages of the mean values: 1.80, 5.26, 8.44, 7.94, 5.65, 6.44, 11.20, and 4.48. These deviations are probably greater than the actual ones because these experiments were performed at the beginning of this study and the technique has improved since then.
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