A very interesting account was given, in the Westminster Gazette
of last Wednesday, of an exhibition by Mr. Herbert Newton of what the Röntgen rays could do in the way of casting shadows through an apparently opaque object on to a screen which has been recently prepared for the purpose at the Royal Institution. When the spectators held up their hands and arms to the Röntgen rays, nothing unusual was observed, but the moment the screen was held up in front of the hand and arm, the shadow of the bones of the hand and forearm could be seen with perfect clearness. And as small parties of spectators were admitted in succession to this strange sight, nearly three hundred persons in all went away extremely excited by having" seen their own bones," an experience which they had never had before. They did not, however, really see their own bones, but only the shadow of their own bones, and as yet this method seems only applicable to those parts of the body which will cast a shadow, in other words, which the Röntgen rays will not penetrate. All parts of the body which are composed of the ordinary tissues, like tumours, for instance, will cast no shadow under the Röntgen rays. "A black leather bag was held up before the radiant tube, and no one could see anything but a black leather bag. On the screen being placed in front of this object, the contents of the bag at once became visible to all the spectators, who saw that the bag contained a box of compasses (the X rays penetrating both the leather of the bag and the wood of the compass case), a pair of spectacles in a case, a box with some nails in it, and various other objects. It may be mentioned that the contents of the bag were wrapped in cotton wool." But if the bag had contained an apple and a mutton chop the apple, we sup- pose, would have cast no shadow, and the mutton chop would have been represented only by the bone without the meat on it. For the purposes of the surgeons, the X rays are not sufficient. They want some Y rays which will penetrate the bones and cast shadows of the healthy or diseased organic tissues.
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