Campagna, Mario J.

After a preliminary observation period, a small lesion was made in the pituitary stalk of 10 dogs. The daily water intake, urinary output, urinary specific gravity and body weight were recorded. Each animal was given water-load tests consisting of a large volume of tap water by gavage. The surgical lesions were verified histologically. Immediately following the surgical procedure there was a marked spontaneous increase in water intake and urinary output lasting approximately 3 days. Each animal subsequently passed through a period of water retention as shown by the water-load test at some time between the 6th and the 10th postoperative day. Following this, the water exchange and the response to the water-load test approximated the preoperative values. The possible physiologic significance of these findings is discussed.