From the medical point of view the perfection of the system offers illimitable opportunities. In the hospital, where a patient may be lying in a critical condition, the surgeon can have a continuous record of the state of his pulse without its being felt by hand at intervals. The physician, in unusual or baffling cases of disease, can have a photographic record of the pulse and heart movements from the moment the symptoms develop until the patient either dies or recovers. It also enables the physician to be informed as to how the invalid is responding to his treatment. Hitherto, the practice has been to feel the pulse at varying specified intervals, to commit the readings to a chart, and then to connect the points by lines so as to show at a glance whether heart movement has accelerated or decelerated, and to what degree. Such charts are satisfactory so far as they go, but they may be erroneous, because the action of the heart may have fluctuated between the readings. With the continuous photographic system, however, guesswork does not enter into the issue at all. The complete story is set down in an unimpeachable graphic manner.
Perhaps the most extraordinary feature of this development is that the very sounds of the heart palpitations can be committed to a sensitized surface in a continuous manner. The principle is much the same as in the case of the record of the heart's movements. There is a small light disk provided with an aperture, mounted upon a stand. Across this aperture is stretched a thread of platinum or quartz. This instrument is placed in the horizontal path of a pencil of light, between the camera and the source of illumination, so that the ray passes through the aperture of the disk to enter the lens of the camera. Consequently the shadow of the quartz thread is thrown upon the sensitized surface in the camera.
A film of soapy water is spread over the aperture in the disk, and this, of course, comes into contact with the quartz thread. The provision of this film in reality converts the disk into a very sensitive diaphragm. Now a stethoscope is placed over the patient's heart, the opposite end of which is connected to the disk in such a way as to bear upon the surface of the soap bubble. When the heart beats the noise which is set up thereby is received by the stethoscope and conveyed to the soap bubble. The bubble, being very sensitive, responds to the sound movement in greater or less degree. As it vibrates, it naturally moves the quartz thread with it, and the moving shadow of the string is caught by the photographic film in the camera.
In this manner the surgeon or observer can have a permanent continuous record of the sound of the heart beats converted into movement, and from the regularity of the oscillations he is able to tell whether the heart is beating regularly. If desired, the record of both the heart-beat as demonstrated by the galvanometer, and the sound of the palpitation as indicated by the soap bubble diaphragm, may be obtained upon one chart, and, in synchrony, so as to set a double check upon the observations.
The chronophotography of continuous movement has been brought to a high stage of perfection by the searching experiments of Professor Einthoven. From the physiological point of view he has contributed most valuable data concerning the heart, for his experiments have been with subjects of all ages and in varying conditions of health. The investigations have been extended to animals also, showing the differences in heart beating phenomena between the various members of the animal kingdom.
By courtesy of the Marey Institute.
Continuous Cinematography.—the Palpitations of a Rabbit's Heart.
The vertical lines indicate the extent of the heart beat, while the horizontal lines give the time interval.
