Abstract
In experiments commenced in April, 1929, and recently completed, tests have been made of the antirachitic value of the ultraviolet emitted by tungsten filaments similar to those used in ordinary electric light bulbs. To secure any appreciable amount of therapeutic rays from such sources, bulbs made of the very best ultraviolet transmitting glass must be used. The Corex D bulbs in the lamps employed in these experiments transmit about three-fourths of the vital ultraviolet given off from the filament. Such lamps, at present provided only for experimental purposes, are designated by their producers, the General Electric Company, as CX lamps.
Six experiments included 255 chickens divided into 23 groups. In 2 of the experiments rats were run in parallel series with the chickens.
We first made use of a 500 watt bulb (vitalux glass) on a 110-volt electric circuit at a distance of 5 feet from the floor. Without reflector and at this distance this source was not adequate for satisfactory cure. Some improvement was noticeable but only to the extent of 10 or 15% in 28 days. Control animals were almost cured in this period with 4 exposures of less than 10 minutes each (37 1/2 minutes in all), from a quartz mercury arc.
We have always heated our small brooders by means of electric light bulbs. When exposed to the rays of 60 watt carbon filament lamps, the chickens invariably develop severe rickets. This has also been the case in 2 earlier experiments where ordinary Mazda bulbs were used.
In the second test no sign of rickets appeared in the pen where a 330-hour CX lamp was kept in the brooder. The controls, having a 60-watt carbon filament lamp in the brooder, all developed severe rickets.
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