THE EFFECTS OF SELECTIVE SOLAR IRRADIATION ON THE PARATHYROID GLANDS OF CHICKS

Abstract

The chicks were kept within doors behind amber, blue, and ordinary glass and vitaglass which transmit known portions of the sun''s spectrum. The basic diet used throughout was the Wisconsin all-mash ration. Half of the chicks under each filter were fed the basic diet alone; the other half were fed the basic diet and 2% by weight of cod-liver oil. All the chicks of each pen thrived equally well during the earlier months of the experiment; signs of weakness of the legs did not develop until they were 5 months old. Enlargement of the parathyroid glands was recognized within the first few weeks in chicks growing under amber and blue glass; this enlargement was due to hyperplasia rather than hypertrophy. The 2% of cod-liver oil added to the basic diet serves to maintain a more nearly normal-sized gland even in the longer wave lengths of sunlight. Both the longer and the shorter wave lengths of sunlight are essential to the maintenance of normal parathyroid glands. Regression of the cell columns is manifested early; the cause is undetermined. Cysts accompany the retrogressive processes that ensue within the gland. These cysts are of 2 types. One is walled off from the remaining portion of the gland by definite columnar epithelium, while the other is enclosed by a series of concentrically arranged flattened cells. There was no organic indication either in blood Ca, blood P or general activity that such parathyroid hyperplasia had arisen.