CHAPTER XIII

COMBINING THE MICROSCOPE AND THE ULTRA-MICROSCOPE WITH THE MOVING-PICTURE CAMERA

One of the most fascinating fields in the whole realm of animated photography is the filming of the infinitely small by the aid of the microscope. In this manner it is possible to catch glimpses of bacterial and microbic life in natural movement, and to throw them upon the screen, where the extreme magnification enables one to follow with ease the motions of a living world invisible to the naked eye. Furthermore, the representation upon the screen is clearer, brighter, more detailed, and easier to follow, than any image seen directly through the microscope. There is an absence of that distortion and unnatural motion which often occur when the microscope alone is used.

Micro-cinematography may be either costly or cheap. As the operator in a well-equipped laboratory is able to use a camera costing £100 ($500), it is only natural to suppose that he will also be able to command the services of the most expensive type of microscope. On the other hand, the independent worker, forced by circumstances to be content with an inexpensive camera, will have to do the best he can with an inexpensive microscope also. Yet the investigator of each class can accomplish excellent work in his own sphere. I have seen some very fine films of microscopic subjects which were taken with an instrument costing less than a sovereign. From the general point of view they compared very favourably with those obtained with an instrument twenty times as costly. So long as the amateur does not attempt to embark upon work which is beyond the capacity of his microscope, and is content to work with subjects of relatively large size, there is no reason why he should not be able to take most interesting pictures.

In the preparation of micro-cinematographic subjects it is essential that the instruments should be mounted upon a solid base, a heavy bench or table, so that vibrations may be as slight as possible. The camera may be turned by hand or driven by an electric motor through belts and pulleys.

The method of mounting the microscope in its relation to the camera may be varied according to circumstances. In the simplest form the microscope is mounted horizontally with the stage on which the subject is placed set vertically, the subject itself being in line with the middle of the cinematograph lens.

In working with the microscope it must be remembered that the objects are seen by transparence. That is to say, the ray of light passes directly through, or around, the object, causing it to stand out darkly upon a luminous background. From this arises one of the limitations of the microscope. If the subjects themselves are wholly or nearly transparent, they become wholly or nearly indistinguishable in the illuminated field in which they are placed. In still-life microscopical study this disadvantage is overcome by colouring the glass slide on which the subjects are deposited, but in cinematography this operation is ruinous to the work for the simple reason that the aniline dye used to colour the slide kills the microbe whose life and movements are to be observed.

It must not be forgotten that very small organisms, as a rule, move at a speed which is quite disproportionate to their size. Some will dart hither and thither across the field of the microscope with the speed of lightning, while others will move with great deliberation. In the first case a photographing speed of sixteen pictures per second will scarcely suffice to give a faithful record of movement. The result will be a series of disconnected jumps. On the other hand, if the object moves slowly, a photographing speed of sixteen pictures per second may be too rapid. In this event the phase of movement between two successive pictures will be so slight that the projection on the screen will appear tame unless the express object is to indicate the slowness with which the organism moves. And indeed this object can be achieved with almost equally good results by taking the pictures at a slower speed, say eight, four, or even two images per second, and thus saving a good deal of film.

In most cases the micro-cinematographer works in a state of ignorance. He does not know whether he is obtaining a good or a bad film. His subject may be moving, or it may be quiescent, or it may hover round the extreme edge of the luminous field, in which case the pictures will be useless. When Mr. James Williamson and Dr. Spitta were engaged on micro-cinematograph studies some years ago, they introduced a means of following the subject through a second tube, and in this way were able to make certain that the camera was working only during those periods when the subject was in full activity, near the centre of the picture. In this way a considerable saving in film was effected.

Another difficulty is the selection and control of the light. Attempts have been made to concentrate solar light by means of a parabolic reflector or lens, and then to throw it through the microscope slide. The great drawback to this system is that intense heat is thrown upon the slide containing the organisms, and for these small creatures heat spells death. The same difficulties arise with acetylene and electric light. What is necessary is either to extinguish the light at intervals, in synchrony with the closing of the lens, or to intercept it so as to keep it off the subject until the exposure is to be made. This is done in a variety of ways by different workers.

Some years ago, when Messrs. Bull and Pizon of the Marey Institute were engaged in the micro-cinema study of a colony of marine organisms, they adopted the apparatus and method of arrangement shown in the illustration facing p. 164. The microscope C was attached to the cinematograph B which was driven by the clock A. In this case it was only necessary to make exposures at relatively long intervals, and to continue them through several days and nights, so as to obtain a complete cycle of the phases of the development of the organisms. Consequently the clock was introduced in order to make the exposures at the right intervals.

The organisms were placed in a small flat glass tank or vessel D, and were illuminated by the light from an incandescent gas burner. As it was unnecessary to keep the burner alight during the periods when the shutter was closed, Messrs. Bull and Pizon introduced a means of turning the light up and down. This was effected by a small electric magnet, working in synchrony with the clock and controlling the light so that the subject was illuminated only during exposure.

As the studies were prolonged it was essential that the water in which the organisms were placed should be kept fresh and sweet. A glass jar F was introduced to serve as a reservoir, and from this a tube extended to the vessel D. A constant flow of water was thus provided. Its circulation was ensured by another glass tube extending from the vessel P to the waste. The flow of water was controlled to a nicety by means of a tap without the production of bubbles or any other disturbance in the vessel D. In this manner the colony was preserved to the best advantage and in full activity. Some such system of circulation is necessary in all cases where the investigations are to last a long time.

In recent years the Marey Institute has much improved its micro-cinematographic apparatus. The microscope is now carried in a vertical position in front of the support which holds the camera. The camera is fitted with an external bellows which carries a prism at its outer extremity. The prism is brought over the eye-piece of the microscope. The rays of light striking the turning mirror on the base of the microscope are projected upwards through the object side or vessel and then through the eye-piece to the prism. Here the rays are bent at right angles, and are thus directed upon the travelling film in the camera. The camera is driven electrically, the motor being mounted within the box forming the base. Mechanism is introduced whereby the number of photographs per second may be varied within wide limits.

The most interesting feature of this apparatus is the means adopted to enable the worker to follow the movements of the object so that the camera can be stopped when they are of no moment or are not sufficiently near the centre of the picture. A small proportion of the light rays which have passed through the microscope are deflected from the prism mounted upon the eye-piece and thrown into a small view finder beside the camera. Looking into this view finder one can see exactly what is happening upon the stage of the microscope. This novel attachment enables the waste of film to be reduced to almost nothing.

The character of the illuminant also can be varied. Sunlight may be caught by the mirror of the microscope and projected through the instrument as well as the beam from an electric light, incandescent gas burner, or what not. With this effective and compact apparatus many marvellous microscopic experiments have been carried out at the Institute, such as the filming of the heart-beats of minute insects, and so forth. One very fascinating investigation was that carried out by Dr. J. Ries, of Switzerland, whereby he secured a cinematographic record of the different phases of the union of the sperm and the egg, as well as the separation of the membrane and segmentation of the sea urchin. The difficulties of such a delicate study were extreme, but the films obtained were of the utmost interest. They enabled the investigator to reconstruct upon the screen the complete phenomenon of fecundation. For this study the subject had to be photographed while immersed in a small vessel containing artificially prepared sea-water, which was renewed as required. The clock control enabled the camera mechanism to be so turned as to secure a regular series of exposures at the rate of seven per minute.

When Dr. Jean Comandon set himself to cinematograph the most minute microbes, which are so small that two million may be found in a cube measuring only one-twenty-fifth of an inch, he appreciated the limitations of the ordinary microscope, and the impossibility of obtaining images clearly and distinctly therewith. So he resorted to the ultra-microscope. With this instrument the light is not thrown directly through the slide containing the object, but is directed upon it by reflection from a light which stands at one side. Beneath the object to be examined is placed a glass prism, or condenser, set at right angles to the optical axis of the microscope, the result being that the light enters the slide through the edge. The objects under examination, instead of appearing as dark objects against a luminous ground as in the direct transmission of the light, appear luminous in themselves and stand out as bright spots against a dark background. By the aid of this instrument, particles which are beyond the scope of vision with the highest powered microscopes may be seen with ease.

Thus this French investigator was able to photograph even the most minute organisms. The well-known firm of Pathé Frères placed their laboratory and resources at his disposal, so that the work might be done under the most favourable conditions. Even then two years passed before a successful detailed film was obtained, and an apparatus made perfect for this class of work.

The complete apparatus is set upon a massive bench, so as to secure absolute rigidity, because vibrations are fatal to good results. Slight modifications are sometimes needed, but in most cases the same appliances are used, and in the same way. The light is furnished from a 30-ampère electric arc lamp. In front of this is arranged a series of lenses for concentrating and varying the rays, while all excess of luminosity is cut off from the microscope by means of a diaphragm. The microscope itself is set horizontally, with its longitudinal optical axis in line with that of the camera, and its eye-piece brought against the camera lens. The camera is one of the Pathé models with detachable dark-boxes.

The ray of light thrown from the electric lamp is concentrated and then falls upon the microscope condenser, which deflects it so that the objects under study become illuminated, no light entering the tube of the microscope. The camera may be turned by hand, or by a small electric motor, the latter giving an improved rotary motion with the least possible vibration.

One of the difficulties which harassed all the early efforts in micro-cinematography was the control of the light so that the subjects might not be killed by the heat generated by the concentrated rays. At first an investigation could not be continued for more than a second or two, because the microbes were killed by the heat. Seeing that the pictures were taken at the rate of sixteen per second, an intermittent lighting system in synchrony with the opening of the lens was difficult to obtain, as there was the risk that the maximum illumination might not be thrown upon the subject at the precise fraction of a second during which the lens was open. Many ingenious expedients were tested to remove this disability, but without success, until at last Dr. Comandon conceived the idea of introducing a rotary shutter, similar to that fitted to the camera itself. This was tried, the shutter being placed between the condensers and the stage on which the objects were set up. This shutter was revolved by the same mechanism as drove the camera shutter, and was so timed that the opaque sector interrupted the ray of light at the same moment as the camera shutter eclipsed the lens. In this way the microbes were protected from the heat of the light while the lens was closed, and it was possible to keep them alive and in full activity in the slide for a considerable time. Repeated experiments suggested improvements in this shutter, and now the scientists employ one in which there are two or three opaque sectors of equal area spaced equidistantly, so that only a flash of light is thrown upon the microbes at the instant of exposure. Still further to lessen the evils of the heat a water condenser has been introduced between two of the glass condensers placed near the lamp. This is a small circular vessel like a big lens. It is filled with cold water and provided with the means to remove the ill effects of bubbling when the temperature rises to boiling point. The system is very much the same as that adopted by the Lumière Brothers when they first used the electric arc for the purpose of projection and with the same object--to protect the inflammable celluloid film from the heat radiated by the light.

With this ingenious and simplified apparatus Dr. Comandon has prepared some very remarkable films which have served to introduce the picture palace patrons as well as the scientists to phases of life about which little was formerly known. When thrown upon the screen the subject in some cases is magnified as many as fifty thousand times, so that the infinitesimal organisms stand up as large as dinner plates and their movements and structure and habits can easily be followed by the eye.

When the earliest films prepared by Dr. Comandon were shown by Dr. Dastre, of the Sorbonne, to the French Academy of Sciences, it was immediately realised that this was a new and reliable means of studying bacteria, and that many questions which heretofore had proved utterly unanswerable could now be solved with ease and precision. A little later the films were introduced to the public, and although it was feared that they would prove of only fleeting interest to the man in the street they have really interested him almost as deeply as the scientists. Good films of bacteria never fail to please a picture palace audience.

At present the preparation of these films is confined to a very small band of investigators. So far as bacteriology is concerned it is expert work, but there are many applications within the reach of the average microscopist. Cinematography has been of use in spreading the knowledge of the facts of health and hygiene, and now that there are propagandist movements on these subjects the aid of the living pictures will be more than ever appreciated.