Abstract
The results of a series of experiments on the biological effect of isolated bands of radiation, show that a 10 minute daily exposure to near infra-red radiation, (ranging from 720-112μμ) of an intensity 0.132 gm. cal/min/cm2, will produce a definite effect upon young rats fed upon a rickets-producing diet. This effect is not fully apparent until the 5th or 6th week of experiment. The radiation causes increased growth of the animals, and prolongs by a period of 4 to 6 weeks their survival on the rickets-producing diet, without conferring any protection against the disease. Infra-red radiation, therefore, acts in a manner different from ultra-violet, and exerts a physiological action whose effect can be demonstrated.
In a limited number of animals examined, this growth-promoting effect of infra-red radiation was found to be associated with marked enlargement and hypertrophy of the thyroid gland. Irradiation with ultra-violet, in corresponding litter-mates, was found to prevent this hypertrophy whether or not the rat was exposed to infrared radiation. This result must be corroborated by further experiment.
Some hyperplasia of the parathyroid gland was observed in a group of rats receiving infra-red radiation. The glands of the corresponding group, receiving ultra-violet, were of normal size.
Ash analysis of the bones of 18 rats protected against rickets with ultra-violet radiation showed slightly higher ratios between the ash and organic residue, than those of a similar group of litter mates that had received in addition to the ultra-violet, a daily exposure to near infra-red radiation.
These experiments have been in progress, in collaboration with Mr. L. A. Jones of the Eastman Kodak Company, for the past two years.
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