Some Considerations upon the Elective Action of the Rays

Abstract

PRACTICALLY, we distinguish two kinds of radiation: (1) heterogeneous, unfiltered radium radiation composed of corpuscular beta rays and all kinds of vibratory gamma rays and the vibratory rays of all possible wave lengths by the X-rays, and (2) more or less homogeneous filtered radiation composed only of vibratory gamma rays and X-rays of the shortest wave length. Is there anything in experimental radiobiology which would correspond to this division? The most conclusive response on this question is given by the experiments with radium rays on striated muscles, tissue which is generally considered as not very sensitive to the rays. If a platinum needle containing a moderate dose of radium salt is placed in the muscles of a rabbit for a fairly long time, two distinctive concentric zones appear around the needle. Gorowitz, Bagg, Lacassagne and others have shown that the first of these zones, disposed nearer to the radio-active focus, is a necrotic area. It is characterized by the coagulation of the cytoplasm and by the destruction of the nuclei. The connective tissue, as well as the muscular, is killed. The second area, sharply defined from the first, is especially characterized by a progressive disappearance of muscular cytoplasm. The latter fact justifies the name of atrophic zone; the outside boundary of this zone can be seen quite distinctly. The destruction of cytoplasm, characteristic of the atrophic zone, is brought about by a process of autolysis; sometimes the muscular fibers simply become thinner, sometimes vacuoles are seen in them. On the other hand, the nuclei prove to be much more resistant, even accumulating in groups or chains. Probably it depends on the fact that the nuclei of the striated muscles multiply by a simple amitotic division and not by mitosis, which is known to be sensitive to the rays. In spite of the atrophy of the muscular fibers, the connective tissue becomes greatly hypertrophied, gradually replacing the disappearing striated muscles. I have obtained a conspicuous development of these two zones, using as little as 1.99 mgm. of radium element, and 0.5 mm. of platinum as filtration, but only after a rather long irradiation, namely, 28 days. After 13 days, no delimited zone of necrosis was formed, only isolated fibers in the vicinity of the needle presented some foci of coagulation of their protoplasm. We thus infer that the formation of the zone of necrosis, when filtered radiation is used, is due to the accumulation of the relatively feeble necrotic effects of the secondary radiation from the platinum through a long period of time. Meanwhile, less evident atrophic phenomena have time to attain their full development.