1. The P.D. between the two surfaces of the skin of the frog, when measured under standardized conditions, may be used as a means of studying the phenomena of injury, recovery, and death. Injurious conditions decrease the P.D.
2. According to the severity of the injury produced by temporary exposure to high temperatures, frog skin may show, as judged by this criterion (a) complete recovery, (b) partial recovery, or (c) a progressive change leading to death.