THE GROWTH AND DEVELOPMENT OF CHICKS AS INFLUENCED BY SOLAR IRRADIATION OF LONG VISIBLE AND ULTRAVIOLET WAVELENGTHS, RESPECTIVELY, WITH AND WITHOUT SUPPLEMENTARY IRRADIATION OF VARIOUS TYPES

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Abstract
Constant housing of chicks behind a filter (red-purple corex) which transmits practically only the ultra-violet region (400-290 m[mu], with maximal transmission of 20% at 330 m[mu]) does not permit normal development and growth as evidenced by wt. Constant housing of chicks behind an amber glass filter which transmits only the longer visible wave lengths of sunlight (500 mu to the end of the visible spectrum) definitely retards growth and development. Supplementary irradiation of chicks, constantly housed behind a filter (amber) which transmits only the long visible portion of the spectrum, with an air-cooled quartz-Hg lamp operated at 90 volts and at 50 cm. (u.-v. irradiation of energy approximately 575 ergs each sec. for each sq. mm.) for 10-15 min. a day induces normal growth and development. Supplementary daily periods of 20 min. of irradiation of chicks constantly housed behind the amber filter with the energy of a quartz-Hg lamp (operated at 90 volts and at 50 cm.) transmitted by purple corex glass (160 ergs each sec. for each sq. mm.) induces normal growth as evidenced by wt., but does not permit normalcy of parathyroid glands. Irradiation with the u.-v. portion (incident u.-v. energy being 575 ergs each sec. for sq. mm.) of a quartz-Hg lamp for 10-15 min. a day is capable of producing normal growth and development. U.-v. irradiation of the heads only of chicks is apparently as effective as (and possibly more effective than) irradiation of the bodies only in establishing normal development and growth, the chicks being housed behind an amber filter. Microscopic investigations (Becke method) on the calcification of tissues (femurs) in chicks about 3 and 5 mo. old, housed behind amber and corex filters and given various supplementary amounts of irradia- tion with the quartz-Hg-arc lamp, showed that normal calcification does not occur in chicks receiving only the long wave lengths of sunlight. The data on growth and development, as judged by wt., closely parallel the degree of normalcy evidenced in the development of the parathyroid glands. Hyperplasia of the parathyroid glands is apparent in chicks housed behind either amber glass (transmitting long visible wave lengths) or corex glass (transmitting u.-v.), and is least evident in chicks that have received irradiation 10 or 15 min. daily with the air-cooled quartz-Hg lamp. Further evidence is presented, therefore, to support the statement that normal growth and development are dependent on both the u.-v. and visible portions of solar irradiation, all other factors remaining constant so far as is known.

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