c4nnula is used which does not expand and contract like an uninjured

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1 THE PHOTOGRAPHIC KYMOGRAPH. BY JOHN BERRY HAYCRAFT. (From the Physiological Laboratory, Cambridge.) recognised that tracings of arteriol blood-pressure, taken with the IT is mercury manometer, do not record rapid changes; in consequence of the inertia of the mercury, they do not show the true variations in pressure caused by the heart beat, indicating as a rule the slower respiratory movements, very much better. In Fick's manometer there is less inertia, but the movements recorded are partly due to inertia and to the period of vibration of the spring. Htirthle's manometer responds also imperfectly to quick-changes of pressure. All of these have the further drawback that the artery is divided and that one does not record changes due to the contraction and dilation of the arteries and capillaries in which it terminates. Another objection is that a glass c4nnula is used which does not expand and contract like an uninjured vessel. In order to obtain a truer record of quick variations of arterial pressure I have devised an instrument for photographing the movements of the artery whilst the blood is circulating through it. The instrument, adopting the suggestion of Professor Langley, may be called the photographic kymograph. The photographic method was I believe first used by Czermak(1) in 1863, and has had many applications since that time. John Parkinson(2) obtained tracings in man by placing the neck in the path of rays of light passing through an electro-cardiograph. He records great difficulty, and his tracings are few in number and evidently difficult to obtain. Many persons have used the photographic method but they have not worked upon the unopened artery, generally experimenting upon the heart. I may mention the names of Otto Frank(3), Van Zwaluwenburg, Agnew(4) and Wiggers(5). The general arrangement of the apparatus is shown in Fig. 1. A beam of light is projected from an electric lamp (Fig. 1 A), on to a mirror (B) and from this the light is reflected through the body of the photographic kymograph to a vertical slit (C) behind which the sensitised paper is drawn. The mirror is a small galvanometer mirror which

2 176 J. B. HA YCRAFT. is slightly concave. It should project a very tiny spot of light upon the vertical slit not more than 1 mm. in diameter. The mirror moves upon _.~~~~~~~~~~F a horizontal axis and is placed in connection with the artery by a method shortly to be described. The sensitised paper is set in position by an electromotor (D) which is hung from the ceiling, and is connected with a grooved wheel by an elastic band. In the axis of this wheel is a wormwheel which s,ets in motion within the instrument a vertical rod between which and another rod the sensitised paper is pulled along. The electromotor being first started, the whole is set in motion by a friction-clutch (E), and the speed at which the paper travels can be regulated not only by shifting the elastic band to other positions in the vertical wheel, but by a change-gear within the instrument. After a tracing is taken the paper may be cut by a vertical knife (F), and the rest of the instrument detached and removed to the dark room. Two very small electric lamps are each of them covered by metal, except for a hole through which a spot of light is projected into the lower part of the vertical slit. One of them is connected by wires (H) with a Brodie's time marker, and gives a spot of light upon the paper every two seconds or less, and the other is arranged in connection with an induction-coil, and gives a horizontal line which corresponds with the time in which a nerve may be stimulated. The mirror (Fig. 2 b, M) is fixed to the centre of a light metal plate, which rotates upon a horizontal axis; it is fixed so that its anterior surface is in a line with this axis. At either end of the plate in this axis is a little cup of metal in which fit the tiny screws (E). The mirror can then swing quite freely. Behind the mirror is a groove of metal in which slides a tiny slip of metal (C) which is bent below

3 PHOTOGRAPHIC KYMOGRAPH. 177 and forward nearly to a right angle (D) and rests upon the artery (A). The pressure of this upon the artery is only a few milligrammes, but in order that this weight should be more distributed, another piece of metal, about a quarter of an inch long, is fastened across it at right angles. This is curved so as to fit upon the artery. Before applying this to the artery it is smeared with thick vaseline in order to prevent it from being thrown upwards after each systole of the heart. By means of the groove behind the mirror it is possible to regulate the movements of the mirror and to make them greater or smaller. In the case of the abdominal aorta of a cat (anaesthetics, A.C.E. and phenaldehyde) it is not necessary to remove the vessel from its attach- PH. LVII. 12

4 178 J. B. HAYCRAF1. ments; the plate in connection with the mirror mnay be placed directly upon it; this is the easiest way to take tracings. In the case of the carotid the respiratory movements of the neck are much bigger and interfere with the result. It is necessary to isolate the artery for about two inches, and to place it upon something which is immovable. The artery is therefore placed in a groove of a piece of ebonite which is supported also upon an upright; it is important that the artery should lie in a normal position. By bending the head (an additional joint was put into the rabbit-holder), this is brought about and the artery can then be placed in position upon the ebonite plate so as to lie in the same line with it. The metal rod holding the mirror can be arranged upon it, and it can be moved by screws up and down, from side to side and from before backwards. These screws are not seen in the figure. It is most important to work with two tables, one for the kyinograph, and the other for the animal, the support for the mirror, and the ebonite plate. The reason is that the vibration of the kymograph would otherwise shake the animal, and the mirror attached to it. In Fig. 1, they are both covered by a sheet for purpose of photography. The aperture in the photographic kymograph through which the vertical slit is seen is covered by a piece of ruby glass. The sensitised papers (Nikko) Kodak Co., are 10 or 5 cm. wide and can be prepared in lengths of 100 yards or more. I have to thank Mr J. Brown for very kind help in preparing them. While the vaseline holds the mirror to the artery of a rabbit and a cat, in the dog the movements are so rapid and jerky that this is not the case, and the results will be dealt with in another paper. In order to determine whether the inertia of the mirror would throw it away from the artery, it was attached to a tuning fork vibrating 25 times to the second, by means of vaseline. The tracing obtained showed an even curve (Fig. 3). Of course the movement of the tuning fork must be small otherwise the mirror would at once fly off As Ray was I believe the first to point out, the expansion of an artery is not a linear measure of the pressure of the blood within it. One cannot therefore record the absolute pressure, but one can safely say that at one portion of the curve the pressure is higher or lower than at another, which is all that one can say for a Ludwig's or a Fick's curve.

5 PHOTOGRAPHIC KYMOGRAPH. 179 Tracings obtained. Fig. 4 shows the normal blood tracing in the rabbit; the tracing could of course be obtained much larger. It will be seen that the respiratory movements are small while those of the artery are large. In many other cases it is hard to see that there are any respiratory movements at all. The variation in the 1g thickness of the lines of course indicates the rate of movement of the artery. Fig..5 shows two curves obtained by stimulating the peripheral end of the vagus. The lower straight lines indicate the duration of the stimulus. The dots indicate time X second. This is like the curve for the mercury manometer except that after the stimulation it does not exceed the upper level of the curve. The difference may probably be due to the flow through the artery being obstructed in the case of the mercurial manometer, and free in the other. Another point in which the tracing differs from that obtained by the mercury manometer is the very much larger curve obtained for each heart beat. The curve obtained by stimulating the depressor nerve is like that given by a mercury manometer except of course that the variations in size due to the heart beats are much more extensive. Fig. 6 shows the tracings obtained by the instrument adapted for the frog's heart; another and much longer piece of metal is placed in the groove at the back of the mirror. There is of course no need of the cross curved L piece which is essential for the artery. I have to thank most heartily Professor Langley for the generous manner in which he adapted a room in his laboratory for my work. 1 have to thank my former mechanical assistant Mr Josiah Miles for the care with which he constructed most of my apparatus. 12-2

6 180 J. B. HA YCRAFT. I have finally and not less warmly to thank the Medical Research Council for their generous gift in aid of the research, a portion of which is here published. REFERENCES. (1) Stzngsb. d. K. Akad. d. Wiss. M-N. Cl. Wien. 47. Abt. 2. S (2) J. P a rk i n s o n. Heart p. 57. (3) 0. Frank. Ztsch. f. Biol. 53. p See Tigerstedt's Hdbh d. Physiol. Methodik 1. iv. p. 1 and 2. ii. p. 1. (4) Van Zwaluwenburg and Agnew. Heart (5) Wiggers. Amer. Journ. of Physiol. p The perfecting -of the instrument described in the foregoing pages had long been close to the heart of Prof. Haycraft. He considered that the existing methods of recording variations of arterial pressure gave a very inaccurate rendering of the actual variations and he hoped to fashion an instrument giving a true record. The short account he has given was to be the forerunner of a full investigation. He had obtained a number of tracings from the arteries both of man and animals, which showed no dicrotic wave and he believed that this wave was artificial-the result of narrowing the lumen of the artery by pressure. Whilst engaged in testing the trustworthiness of the tracings, death struck him down, and his work is left for others to complete. J. N. L. U