Abstract
The occurrence of a seasonal and annual variation in the goitre-producing power of cabbage and other plants has been previously reported. 1 At that time it was suggested that sunlight might be a factor in bringing about the synthesis of some substance in the cabbage responsible for the production of goitre. Freshly harvested cabbage, from a source which had previously been known to produce active goitrogenic plants, was finely divided, spread in layers from 1 to 2 cm. thick, and irradiated with a carbon arc for 20 minutes at a distance of 50 cm. The maximum intensity of the arc used was between 3500 and 4000 A. U. The cabbage was then fed to normal rabbits in quantities equivalent to 60 calories per kilo per day. The experiment was controlled by feeding hashed, unirradiated cabbage from the same source in equivalent amounts to a similar series of rabbits. All rabbits used in the experiment were injected subcutaneously with 5 mg. of potassium iodide one week prior to the beginning of the experiment, to insure complete involution of their thyroid glands. At the termination of the experiment, the condition of the thyroid gland was determined during life by its exposure under ether anesthesia. The animals were later sacrificed and the weight of the thyroid was taken at autopsy.
A second experiment was carried out under the same conditions except that a batch of cabbage with less goitre producing activity was used. The thyroid glands were exposed at operation but the animals were not later sacrificed. Table II shows the results of this experiment.
It would appear that carbon arc irradiation increases the goitre producing power of cabbage. It would seem that light brings about a photochemical reaction in the plant with the consequent formation of the goitrogenic substance.
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