Abstract
Summary
1) Definite suppression of growth of treated portion of the head was observed 80–110 days after irradiation with 3,000 or 6,000 r. In irradiated portions: teeth disappeared completely, growth of olfactory chambers suppressed greatly, but they never disappeared completely, anterior portion of the lower jaw had disappeared, visceral arches all shifted in rostral direction, development of the eyes was suppressed. According to sensitivity, it is possible to distribute the tissues and organs among 5 groups. (I) The teeth and lymph nodes (disappeared completely in 100% of animals). (II) Olfactory epithelium and the lens (disappeared in 28%, damaged in 55% and normal in 17%). (III) Epithelium of the cornea (disappeared in 30%, damaged in 38% and normal in 32%) and the rods and cones layer of the retina (disappeared in 31%, damaged in 33% and normal in 36%). The gills. (IV) Other layers of retina (damaged in 16% and normal in 84%). (V) Pigment cells of choroid and other tissues of the head, which are comparatively resistant and did not show any clear signs of damage. 2) Specialized but not completely differentiated tissues can be destroyed by X-ray irradiation and after this never restored, being replaced by typical skin epithelium with Leydig's cells. This was observed in oral epithelium, olfactory epithelium and epithelium of the cornea.
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