Neurology

WITII the aid of the Horsley-Clarke stereotaxic instrument, lesions were placed in various parts of the hypothalamus in 40 adult cats. In 10 instances prolonged and permanent polyuria developed, while in two cats transient polyuria was observed. In seven of the cats with permanent polyuria transient diuresis which preceded the onset of the permanent phase occurred. The transient polyuria was followed by an interval during which normal conditions of water exchange prevailed. In six instances the interval between the day of operation and the onset of the permanent polyuria varied from eight to 12 days. This interval has been called the latent period. The transient polyuria has been found to differ from the permanent polyuria in the following respects. It develops much more rapidly and reaches a peak much sooner than does the permanent polyuria; the polyuria is primary to the polydipsia during the permanent phase, while the intake of fluid usually exceeds the output of urine on the first day of the transient phase; during the transient phase the output of urine and the intake of fluid may reach proportions never observed in the permanent phase. The polyuria and polydipsia in the 10 diabetic cats lasted from two to nine months and appeared to be permanent. The output of urine and the intake of fluid for the animals with the most severe diabetes insipidus were five or six times greater than the values for the control animals. As the polyuria increased in intensity the specific gravity of the urine became correspondingly lower. Deprivation of water for several days brought about a reduction in the output of urine to a normal level and deprivation of food resulted in a reduction of the output of urine to about one-half the previous level. During the course of the experiments on the deprivation of water. the animals lost considerable fluid and a negative water balance developed, suggesting that the polyuria is primary. Repeated small doses of pitressin injected subcutaneously caused a reduction in the urine output and the fluid intake to normal levels. Permanent polyuria was found to occur only in the cases in which there was bilateral injury to the supraoptico-hypophyseal system. Such