CHAPTER XXV.

THE ROENTGEN OR X-RAYS. GEISSLER TUBES--VACUUM TUBES OF CROOKES, HITTORF AND LENARD--THE CATHODE RAY--ROENTGEN’S GREAT DISCOVERY IN 1895--X-RAY APPARATUS-- SALVIONI’S CRYPTOSCOPE--EDISON’S FLUOROSCOPE--THE FLUOROMETER--SUN BURN FROM X-RAYS--USES OF X-RAYS. The majority of people have been accustomed to regard light as something to be excluded and controlled by opaque screens just as effectively as rain is excluded by a tin roof, or cold is kept out by a brick wall. The shady retreat furnished relief from the garish day to the primitive man, and the opaque shades and Venetian blinds of modern civilization exclude the excess of light at our windows. Sunshine and shadow have, in fact, been correlated conditions to the ordinary observation of man since time began. The last few years of the Nineteenth Century, however, were to witness the discovery of a new kind of light ray which, in its behavior, subverted all previous conception of the nature and action of light. It was a species of electric light, which we are accustomed to regard as brilliant, but this light ray was invisible to the eye. It could not be refracted or bent from its course by a prism or lens, and it was so subtle, penetrating and insidious, that it could not be barred out like sunlight, but passed readily through many opaque substances, such as wood, flesh tissue, paper (even a book of 1,000 pages), as well as some of the metals. The lighter the weight of the substance, or less its density, the easier these rays passed through it, or the more transparent such bodies were to the rays. The heavier metals, like platinum, gold and lead, were practically opaque, or allowed none of the rays to pass through them, while the very light metal aluminum was about as transparent to these rays as was glass to ordinary light, and for that reason this metal could form window panes for such rays, while excluding other light. Most organic substances are transparent or semi-transparent to these rays, and hence such rays readily pass through the body of an individual, being only intercepted in part by the denser parts of the anatomy, such as the bones, so that a man in such light no longer casts a well-defined shadow of his outline, but the shadow disclosed is that of a skeleton, by virtue of the greater density of the bones. Any object of higher density, such as a ring upon the finger, clearly establishes its shadow by virtue of its greater density. Likewise, any foreign object in the body, such as a bullet from a gun-shot wound, or a foreign body accidentally swallowed, is perfectly disclosed and located by the shadow which it casts. As these light rays have been characterized as invisible, it may be difficult to understand how invisible rays can cast a visible shadow, and it should be here stated that when these unseen rays fall upon certain chemical substances the latter are made to glow with a peculiar fluorescence, and a screen made of such fluorescing materials will light up where the rays fall upon it, and remain dark at the points where the rays are intercepted by a substance opaque to such rays, thus outlining a shadow. Not only do these light rays in passing through the body tissues (transparent to them) cast a shadow of the bones or any foreign objects, but by the application of photography to these shadow pictures a species of photograph, called a radiograph, or skiagraph, may be taken, and thus any foreign body, such as a bullet, may be definitely located in the human body and quickly extracted, without the element of doubt which beset the old method of diagnosis, which, at best, was only intelligent guessing. Not only are foreign bodies so located, but the fractures of the bones may also be accurately observed, studied and adjusted. Stone in the bladder may be discovered, and the condition and movements of the heart and lungs ascertained. This new kind of light ray was discovered November 8, 1895, by Prof. W. C. Roentgen, of the Royal University of Wurzburg, and was named by him the “X-Ray,” probably because the letter x in algebraic formula represents the unknown quantity, and the hitherto unknown and elusive quality of this light suggested to Prof. Roentgen this appropriate name. As before stated, a peculiar quality of the X-Rays is that they are not visible to the eye. A beam of X-Rays, thrown into a dark chamber through an aluminum window, would produce no illumination whatever in the room, but such rays would still penetrate the room, and if a fluorescing screen were placed in their path it would instantly light up. It is not surprising, therefore, that these subtle rays should have so long eluded the observation of the scientist. A brief sketch of the conditions leading up to the discovery of the rays is necessary to a proper understanding of the same. [Illustration: FIG. 215.--THE CATHODE RAY.] Every student of physics remembers the old-time lecture room experiments in which the Geissler tubes, with their beautiful play of colored lights, illustrated the action of the electrical discharge from the glass plate machine or the Ruhmkorff coil, on rarified gaseous media. Electrical experiments in high vacua by Sir William Crookes, and by Hittorf and Lenard, have greatly added to the present knowledge in this field, and paved the way to the discovery of Prof. Roentgen. It was known that a vacuum tube, variously called after the names of these scientists, as a Crookes, Hittorf, or Lenard tube, having platinum electrodes sealed in its ends, would, under the static discharge of electricity through it, give peculiar manifestations of light. One of the conducting terminals of such tubes was called, in electrical parlance, the “anode,” from the Greek ανα (up) ὁδος (way), meaning the way up or into the tube, and referring to the entering path of an electric current, or its positive pole; while the other was called the “cathode,” from κατα (down), ὁδος (way), meaning the way down or out, and referring to the outgoing path of an electric current, or its negative pole. When such glass tube, partially exhausted of air, received through its anode and cathode terminals a discharge of static electricity, a peculiar manifestation of light is seen between the anode and cathode terminals. At the anode it appears as a peach blossom glow, and at the cathode it appears as a bluish green light. If the exhaustion of the air in the tube is carried very high, approaching a perfect vacuum, or to about one millionth of the atmospheric pressure, the glow light at the anode disappears, and that at the cathode increases until it fills the entire tube with its characteristic light. This is called the “cathode ray,” or “cathodic ray,” an illustration of which is given in Fig. 215, where the cathode ray is seen in a Crookes tube emanating from the negative pole N or cathode _a_, and casting a shadow of the Maltese cross _b_ into the end of the tube, as seen at _d_. Many of the characteristics of the cathode ray had been observed prior to Prof. Roentgen’s discovery, which, briefly stated, grew out of the following observation: He noticed that when a vacuum tube illumined by the cathode ray was completely masked or covered up by an external shield of black paper, so that no illumination of the tube was visible to the eye, there still passed through it certain subtle rays of light, invisible to the eye, but which would instantly illuminate a sheet of paper coated on one side with barium platino-cyanide, even at a distance of two yards or more, and that these invisible light rays were capable of passing through many substances opaque to ordinary light. He also discovered that these rays could be made to take a shadow photograph on a sensitive plate without even exposing the plate in the usual way, the X-Rays passing freely through the opaque ebonite or pasteboard screen of the plate holder. It did not take the scientific world long to realize the immense importance of this discovery, and to-day X-Ray apparatus constitutes the greatest addition to the surgeon’s resources that has ever been made in the form of mechanical appliances, since by its aid any foreign body in the human frame of greater density than the flesh may be at once definitely located and extracted, or any fracture of the bone disclosed, as the case may be. In the illustration, Fig. 216, is shown an X-Ray photograph of the hand of a gentleman whose thumb bone has been destroyed by disease. [Illustration: FIG. 216.--X-RAY PHOTO OF HAND, SHOWING DISEASED THUMB BONE.] Soon after the announcement of Prof. Roentgen’s discovery, apparatus was devised for seeing with the naked eye the image formed by the shadow of the X-Rays. Prof. Salvioni constructed such a device and described it before the Rome Medical Society as early as February 8, 1896. He called it the “cryptoscope.” It was quite a simple affair, and consisted of an observation tube with a lens, having in front of it a screen of fluorescing material, such as platino-cyanide of barium. When the object to be examined, the hand, for instance, was held in front of the fluorescing screen, and the X-Rays from the vacuum tube fell upon the hand, located between the vacuum tube and the fluorescing screen, a shadow of the bones was cast on the fluorescing screen by virtue of the greater density of the bones, which shadow was clearly discernible to the eye at the end of the observation tube. By this device one was able to see his own bones through the flesh. A device, invented by Edison and called the “fluoroscope,” was constructed on substantially the same principle. This used a tapered observation tube like the old-fashioned stereoscope box, which had at its outer wide end the fluorescing screen, and its small end fashioned to fit the forehead and strapped thereto so as to enclose both eyes. This device is shown in Fig. 217, in which an X-Ray vacuum tube is housed in a wooden box, on which the hand of the patient, or other part to be viewed, is laid, the X-Rays passing readily through the top of the box and casting a shadow of the bones of the hand, or foreign body, on the fluorescing screen of the observation tube. Edison’s experiments also led him in constructing his fluorescing screen, after testing a great number of substances, to select the chemical known as calcium tungstate, instead of the barium platino-cyanide, since the calcium tungstate appeared to give better results in fluorescing. Many other chemicals can be used, however, for making the fluorescing screen, such as the sulphides of calcium, barium and strontium. A recently discovered and powerful fluorescing substance is the double fluoride of ammonium and uranium, discovered by Dr. Mecklebeke. Such fluorescing materials are spread in a thin layer on the side of the screen next to the observer in the viewing apparatus. [Illustration: FIG. 217.--EDISON’S SURGEON’S X-RAY APPARATUS.] It is not to be understood that such viewing apparatus is necessary in taking a surgical photograph. In such case only the X-Ray tube, means for exciting it, the patient’s body, and the sensitive photographic plate, are essential factors, the patient’s limb or body being interposed between the light tube and photographic plate, so as to cause the X-Rays emanating from the tube to cast the shadow of the patient’s bones, the bullet in his body, or other foreign object, directly upon the photographic plate, the sensitive and conscious plate obeying the will of these subtle rays, and receiving the impress of their actinic effect under conditions which it denies to ordinary light. [Illustration: FIG. 218.--COMPLETE X-RAY APPARATUS IN USE.] For exciting the vacuum tube any electrical machine capable of throwing a series of sparks across a gap of about five inches is sufficient. Various electrical machines may be used for this purpose, the Holtz, or the Wimshurst glass plate machine, the Ruhmkorff, or induction coil, or even the high frequency transformer. A good example of a complete X-Ray apparatus is that in use at the Army Medical Museum at Washington, made by Otis Clapp & Son, and shown in Fig. 218. The electrical generator is of the Wimshurst type, and is shown in a large glass-enclosed cabinet on the right. The glass disks within are rotated either by a small electric motor shown on the floor, or by a hand crank above. The X-Ray tube, of globular or bulb shape, is shown just above the patient’s hip, and its opposite poles are connected by wires to the opposite electrodes of the generator. When the current is switched on by the operator, the bulb is illuminated with the cathode rays, and the X-Rays, proceeding therefrom through the clothing and flesh of the patient, cast a shadow of the patient’s hip joint upon the photographic plate placed on the cot beneath the patient. [Illustration: FIG. 219.--X-RAY FOCUS TUBE.] In the effort to secure greater sharpness in the image cast by the X-Rays, various forms of vacuum tubes have been devised. That shown in Fig. 219 represents one of the most important improvements. K is the cathode plate, formed of a concave disk of aluminum, which focuses the rays at a point near the center of the bulb. At this point a plate of platinum A, which metal allows practically none of the X-Rays to pass through it, is mounted on the anode in such an angular position that it gathers the focused rays and reflects them through the side of the tube. They thus make a sharper shadow than when radiating from the more extended surface of the glass. [Illustration: FIG. 220.--LOCATING A FOREIGN BODY IN THE BRAIN.] In Fig. 220 is shown an X-Ray tube, as applied for locating a foreign body in the brain cavity, in which view the patient’s head is interposed between the X-Ray tube and the fluorescing screen, or photographic plate, as the case may be; while Fig. 221 shows the application of the same devices to the body. In both these views the particular form of X-Ray apparatus is known as the “Fluorometer,” made under the Dennis Patent, No. 581,540, April 27, 1897, and it is devised with reference to more accurately locating the foreign object by its shadow, for which purpose adjustable bracket-sights, seen in Fig. 221 on opposite sides of the body, are provided for bringing the X-Rays into proper alignment for projecting the shadow of the foreign body in true indicative position on the fluorescing screen, while a cross hatched grating behind the body, graduated in aliquot spaces of an inch, furnishes a measured field, and forms an easy and quick means of platting the position of said object. In the position of parts in the two figures the horizontal line, on which the foreign object lies, would be determined, but it would not indicate how deep in the object was, _i. e._, whether it was in the middle, or on one side. To determine this the fluorescing screen and grating are placed under the patient, and the X-Ray tube above, and the vertical line of the object is thus obtained. Both the vertical line and horizontal line having been obtained, it will be obvious that the foreign object will lie at the intersection of these two lines, which establishes for the surgeon its definite location. [Illustration: FIG. 221.--X-RAY APPARATUS APPLIED TO THE BODY.] It has been observed by Prof. Elihu Thomson, and also by Dr. Kolle, that the X-Rays are not absorbed and destroyed by the sensitive chemicals of a single photographic plate, but so potent and penetrating is their influence that the rays pass through and produce an image on a number of plates, placed one behind the other, thus affording means for multiplying the image at one exposure. Among other uses of the X-Ray may be mentioned its capacity to detect spurious from genuine gems, the diamond giving a distinct color from its imitations, as do also most other precious stones. A peculiar physiological effect of the X-Rays is their capacity to produce a severe effect on the skin, somewhat resembling sunburn. Such result, produced by long and continued exposure, has sometimes so deranged the skin tissues as to make sores that resulted in the entire loss of and renewal of the skin. The discovery of the X-Ray by Prof. Roentgen may be fairly considered one of the most wonderful scientific achievements of the century, and his first memoir in 1895 is so full, clear and exact, as to have left very little more to be said about it. It is to-day, as it was found by him in 1895, the same mysterious, unseen, but positive force, a species of electrical energy without a domicile, and needing no conductor, a form of light passing through closed doors, invisible itself, and yet lighting up certain substances with a halo of glory, and radically changing and decomposing others. Rivaling the sun in actinic power, and writing its autograph with an unseen hand, it is truly called the X-, or unknown, ray.