Abstract
Since the work of Brunn 1 it has been shown by several other investigators that frogs (Rana pipiens) when injected with pituitrin, increase markedly in weight due to the absorption of water. This increase, occurring in the case of frogs, gave rise to the problem of comparing the amount of water uptake in different animals in the class Amphibia when similarly treated.
The animals selected for this comparative study were: the toad (Bufo americanus), mud puppy (Necturus maculatus), and two species of frogs (Rana pipiens and Rana clamitans). This selection affords a wide variation in natural environmental conditions, the toad living in dry surroundings and the mud puppy constantly in water; as to the 2 species of frogs used, the pipiens reside primarily in damp, marshy fields some distance from the streams, while the clamitans are found more or less submerged in pools of water along the stream's edge. The experiments were carried out in the late summer and early fall.
The procedure was similar to that used in previous experiments. 2 The animals were nearly submerged in tap water at room temperature for at least 12 to 18 hours before the experiment. They were then removed from the water separately, dried with gauze as uniformly as possible, and weighed accurately to one-tenth of a gram. They were next injected subcutaneously with obstetrical pituitrin (Parke Davis), one-tenth cc. per 10 gm. of body weight (one international unit), and again returned to the water. Routine weighings were made at one-half to one hour intervals for 7 to 10 hours. Any changes in weight were calculated on the basis of percentage variation from normal. In all cases the experiments were controlled with uninjected animals kept in the same environment and weighed at the same time intervals.
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