Abstract
Hinrichs and Johnson 1 observed that “short exposures in the region of the sino-auricular node of both frog and turtle produced a noticeable increase in rate.” Also, these investigators found that “it has been possible to stimulate the heart of a frog to regular beat, normal in sequence and in amplitude, by radiation at the sino-auricular node after the heart has been quiescent for an hour or more.” They did not report any amplitude changes after radiation of the normal heart.
The effect of ultraviolet radiation on the exposed heart of the pithed frog, Rana pipiens, and decapitated alligator, A. mississippiensis, immersed in Ringer's solution which was kept at a fairly constant temperature of 12-14°C., was observed during irradiation by a Cooper-Hewitt Quartz Mercury Arc or a General Electric S. 1 lamp at 50 cm. from the preparation. The former was the source employed unless otherwise stated.
Several series of experiments were performed and the following facts were noted:
1 Freshly prepared normal hearts were found to exhibit a slight increase in frequency and amplitude upon irradiation for short intervals (5-10 minutes) after which both indices rapidly fell below the normal and exhibited a delayed and slow recovery. A normal untreated preparation, under the conditions employed during the course of this investigation, exhibits about a 10% fall in amplitude after 3 to 4 hours while the change in frequency may be regarded as negligible.
Get full access to this article
View all access options for this article.