CHAPTER XII

RADIO-CINEMATOGRAPHY: HOW THE X-RAYS ARE USED IN CONJUNCTION WITH THE MOVING-PICTURE CAMERA

With the perfection of radio-photography it was not surprising that the cinematograph investigator pressed this new development into service. It opened up a wide and fascinating field for moving pictures. When the Röntgen rays were first introduced there was one serious handicap to photography by their means--the length of the exposure. But the chemist and the scientist speedily removed this adverse factor, and now X-ray photographs can be taken instantaneously--60 per minute.

Long before this achievement Radio-photography had been yoked with the moving pictures. It was a difficult problem, but it was solved. One scientific inventor stands out prominently in this connection. This is Monsieur M. J. Carvallo who, during his position as sub-director and secretary of the Marey Institute, spared no effort to harness the X-rays to cinematography. Another illustrious worker is Dr. J. Comandon, who may be said to be the pioneer of the popularisation of cinematographic science. It was he who first appealed to the public with films of this character under the auspices of the well-known firm of Pathé Frères. He has been responsible for the preparation of many most interesting films. Both of these workers have shown what can be achieved in this direction, while the fact that they proceed upon totally different lines adds value to their work. It enables their followers to decide for themselves which principle is likely to produce the most satisfactory result in each case.

Strictly speaking, Monsieur Carvallo's methods would appeal more strongly to the scientific mind, bent upon the discovery of some abstruse phenomena, and indifferent to the complicated process involved. The methods of Dr. Comandon, on the other hand, from their enhanced simplicity, will attract the average worker. This investigator makes a special point of accomplishing his end in as simple a manner as possible.

From this it will be judged that radio-cinematography may be expensive or inexpensive. This is a correct assumption, but the amateur investigator need not fear that the deeper researches are beyond his reach. In justice to Monsieur Carvallo, it must be mentioned that his experiments were undertaken at a time when radio-photography had not reached its present stage, and therefore he had to contend with certain difficulties which no longer exist.

Monsieur Carvallo was probably the first worker to attempt to portray in movement the elusive and peculiar features revealed by the Röntgen rays. One or two other scientists had dabbled in the art, but their achievements were not very convincing for the simple reason that they did not employ chronophotography. Monsieur Carvallo, however, being fully aware of the valuable work that had been carried out by Dr. E. J. Marey, saw the true way of applying radiography to cinematography, and saw that it could not fail to be of scientific value. He embarked upon a number of illuminating, though tedious, experiments, in the effort to combine these two branches of photography.

Carvallo's installation was of a most elaborate character, but he accomplished some marvellous results, the full significance of which are appreciated only to-day. The complete apparatus he used in his experiments is shown in Fig. 9. The source of energy was a small electric motor, capable of making 2,000 revolutions per minute with a current of only 50 volts. This motor was extremely sensitive, since it would make 300 revolutions per minute with a current of 10 volts. The control of the speed was essential to his work, so he elaborated a simple and ingenious change-speed gear mechanism, which enabled him to drive the camera at four different speeds without touching the motor. The gear mechanism was not dissimilar from that adopted upon a larger scale in automobiles, lathes, and other machinery where the speed has to be varied according to the character of the work. The direct drive was transmitted from the motor-shaft to that of the camera mechanism through a belt and pulleys so as to secure flexibility and immunity from shocks. The three lower speeds were transmitted through gear wheels. These sets of wheels were mounted upon two parallel shafts and worked upon the sliding principle, which was found to be the simplest and most effective. In order to reduce the noise arising from the meshing and working of the gears the smaller wheels were made of fibre.

By this gearing system it was possible to vary the speed of the camera from 30 revolutions per second to one turn in 15 seconds. When still slower speeds were desired, upon the one-turn-one-picture principle, the motor was cut in and cut out intermittently so that the exposure could be varied from once in 20 seconds to once in an hour or more. Of course, in those instances where the exposures only needed to be made at relatively prolonged intervals, the driving motor was started up intermittently so as to move the shutter at the required moment. A pendulum clock was introduced into the electrical circuit, together with a novel relay. The clock-face was provided with a ring around the dial, with the hour intervals represented by contacts instead of figures. The clock was fitted with one hand only. One electrical lead was connected to the contact ring and the other to the pivoted end of the clock-hand. When the latter came against one of the contacts the electrical circuit was completed, the motor was set in motion, and the camera mechanism was given one turn--sufficient to make an exposure and to jerk the film forward the desired distance through the gate for the next exposure. Obviously this clock system is capable of variation as desired. The contacts may be disposed to coincide with intervals of a second, a minute, an hour, or more between successive exposures. It was necessary to ensure that the contact was of sufficient duration to complete the cycle of camera movements, and, on the other hand, to prevent the motor movement being so prolonged that more than the requisite exposure and movement of the film would be made. This was effected by means of a brake, which arrested the movement of the motor after the exposure had been completed.

With this seemingly complicated apparatus it was possible to take any desired number of successive pictures and at any intervals of time with unerring precision.

For these particular experiments a special film was prepared, for the pictures produced by the standard camera were not large enough. Monsieur Carvallo took pictures of a depth of 2-2/5 inches instead of the usual 3/4 inch. Special arrangements were made also to secure extreme sensitiveness of the emulsion so that it might be more susceptible to the action of the X-rays. The disposition of the film followed special lines, as may be seen by reference to the diagram (Fig. 9). The Crookes tube, containing the X-rays, was placed beneath a table provided with an aperture upon which was laid a transparent medium, such as glass, to support the subject under investigation. Above this was placed the gate through which the film was moved intermittently, the sensitized ribbon travelling in a horizontal direction from one spool to the other. In the early experiments a Maltese cross movement was incorporated to provide the requisite intermittent motion to the film, but subsequently a novel claw motion devised by Monsieur Noguès, the mechanician to the Marey Institute, was introduced with far better results.

In carrying out the experiments with different live subjects extreme ingenuity was used in placing and holding the creature so that the most perfect images might be obtained. Monsieur Carvallo devoted his energies largely to radio-cinematographing the functions of digestion, and selected such subjects as fresh-water fish, toads, frogs, lizards, birds, and mice. Thus he obtained comparative results from five species of the animal kingdom. The subjects were fed first with a special diet, comprising a mixture of flour, sugar, peptone, sub-nitrate of bismuth, and water or milk. The chemical, sub-nitrate of bismuth, was used in order to give the alimentary canal the necessary opacity to secure the best results under the Röntgen rays. In the case of the trout the chemical was injected into the blood.

In order to obtain sharp, clear, and distinct pictures upon the film, the subject under study had to be fixed in an immovable position. In the case of a trout a small celluloid envelope was made, fitted at each end with a small glass tube through which water necessary to the fish's existence was passed in a continuous stream. This vessel was only just large enough to contain the fish, so that movement was quite impossible. The top of the vessel was closed with a sheet of paraffin paper, which was placed in front of the aperture of the film gate. It was a very novel and successful means of radio-cinematographing a fish under natural conditions. The fish themselves appeared to suffer no ill-effects from the method adopted to keep them alive, a trout in one instance being kept in this confined position for two consecutive days. So long as an adequate supply of fresh water was passed through the celluloid vessel in which it was encased it experienced no trouble in respiration.

In the case of the toad and frog the subject was kept in a prone position by attaching thin ribbons to the legs and extending the latter to their utmost so that the digestive organs might be radiographed clearly, distinctly, and without difficulty. The lizard, which is very difficult to photograph, was secured in a similar manner. The birds likewise were attached by their legs, and had their wings extended so that the body came directly in the path of the rays. When young birds were under investigation it was necessary to maintain a circulation of warm water around their bodies so that the temperature might remain constant; otherwise the digestive functions might have been disturbed, thereby invalidating the value of the pictures. In one investigation a fowl was placed in a plaster cast so as to hold it perfectly still and steady.

The photographic speed was varied according to the character of the investigation and the subject. Thus, in recording the digestion in the stomach and intestine of the trout, an exposure was made every twenty seconds. In the case of the toad the speed was one in every ten seconds, while the chicken required one in every five.

One of the most novel experiments which Monsieur Carvallo carried out in this particular field was to ascertain the extent to which digestion will continue in the intestine after it is removed from the animal. The digestive tube of the frog was selected for this novel investigation and the photographs taken at the rate of one per second illustrate the fact that the digestive organ will continue its functions long after its removal from the body.

Since the year 1900 when Monsieur Carvallo carried out his scientific researches with the Röntgen rays, radiographic science has made great strides. Researches of this character no longer require elaborate and expensive apparatus. This has been shown by Dr. J. Comandon, the well-known French scientist, who, at the laboratories of Messrs. Pathé Frères, has prepared some magnificent X-ray films in such a manner as to make them interesting to the average patron of the picture palace. Dr. Comandon possesses the unique ability of so treating his subject as to make it appeal to the unscientific mind.

In his system Dr. Comandon does not radio-cinematograph directly in the manner of Monsieur Carvallo, but has recourse to the fluorescent screen, thereby obtaining his results much more simply and easily. By this means, also, he is able to use the standard cinematograph camera and film without any modifications, the images upon the sensitized celluloid ribbon being of the normal size. The general arrangement of the apparatus used by this investigator is shown in the diagram (Fig. 10). A room is divided by a partition A. On one side is placed a camera F of the conventional type. On the other is the necessary electrical apparatus. An aperture B is provided in the partition, and this space is filled with a fluorescent screen. On one side of the partition A centrally in regard to the fluorescent screen, and a little distance therefrom, is placed the Crookes tube C, the subject under investigation being placed between the tube and the screen. Consequently, the radiograph is projected upon the fluorescent screen and this image is then photographed by the camera. At the normal photographing speed the exposure is about 1/32 second.

The fluorescent screen employed by Dr. Comandon is of the type known as "reinforced." It is covered with tungstate of calcium, instead of barium platino-cyanide. With this screen the Röntgen rays are intensified, or rather are transformed, the luminous radiation being rendered more actinic and therefore able to act more quickly upon the emulsion of bromide of silver with which the film is coated. By using this fluorescent screen the exposure is reduced to about one-tenth of what would be required were the subject radiographed direct.

The high tension current is supplied from an apparatus of a special type E with which a current as high as 100,000 volts can be obtained. Another prominent feature is the high tension interrupter D, which cuts the electric circuit of the tube in and out, in synchrony with the camera mechanism. Thus the Crookes tube is active while the shutter is open but inactive while it is closed.

This interrupter consists of a small glass vessel, charged with petrol, and sealed with a cover of insulating material. Within the vessel, and spaced about 2 inches apart, are two brackets, which extend through the sides of the receptacle through hermetically sealed joints. To these brackets the positive and negative wires are coupled. Above the brackets, and moving within the vessel, is an inverted U-shaped piece. This slides up and down through apertures provided for the purpose in the insulated cover. When lowered to its full extent the arms rest upon the brackets, to which the wires are attached, and this contact completes the electrical circuit. A pulley wire is fixed to the centre of the inverted U-piece to allow it to be moved up and down as required. The up-and-down movement serves as a make-and-break for the circuit. A lift of a quarter of an inch suffices to break the circuit, which lift is effected by the mechanism of the camera over a system of cords and pulleys. Thus, when the camera handle is turned to open the shutter, the contact piece in the interrupter is lowered, the circuit is completed, and the Crookes tube is brought into use. Directly the shutter is closed the contact piece is raised and the tube is disconnected. This simple control permits the exposure to be varied from five or six to sixteen exposures per second, while the tube can be kept continuously at work for as many as fifty-five seconds if desired.

The camera is fitted with a lens made from quartz, which permits the maximum quantity of the actinic rays to pass through to the sensitized film. The film is covered with an exceptionally sensitive emulsion in order to ensure the best results possible with very short exposures. In order to protect the spools of film in the camera from the actinic properties of the rays diffused from the fluorescent screen, the boxes are covered with sheet lead, while the operator is protected with a lead apron, such as is used generally in Röntgen ray investigations.

The many interesting films which Dr. Comandon has produced offer adequate testimony to the practicability and success of the system which he has evolved. Undoubtedly it is the simplest and most inexpensive method of "radio-cinematography" which has been brought into practical operation up to the present, and it is one which may be followed by the private investigator with such modifications as may suggest themselves in particular cases.