The Effect on the External Parathyroid Glands of the Exposure of Rabbits to Ultra-violet Light

Because many instances have been observed of the effects of light on metabolic processes, and because in the higher animals tbe glands of internal secretion act in part as chemical regulators of metabolism, we are undertaking certain studies on the effects on the endocrine tissues of exposure of the skin to ultra-violet light. In preparation for these studies it seemed desirable to make preliminary observations on the reactions of all the ductless glands available for examination, and to note such changes in weight and microscopic appearance as might indicate abnormal activity. Such a study is the more necessary because of various interrelationships among the endocrine glands that make isolated observations on a single tissue of doubtful value. Dr. Wade H. Brown and Dr. Louise Pearce have directed attention to this interdependence among certain of the glands of internal secretion in connection with their extensive studies on experimental syphilis and carcinoma in the rabbit. During the past 2 years they have collected data on individual and seasonal variations in the size, appearance, and functional activity of the endocrine tissues of a large number of normal animals. 1 These valuable records, mostly unpublished, they have kindly placed at our disposal. It would have been fruitless to make the observations on which this paper is based without the extensive control material thus afforded us. Even during the period covered by the experiments--November to February--there occurred in certain of the endocrine tissues a change, regarded as