« PreviousContinue »
Hand-sphygmoscopes placed upon the carotid, the brachial, the radial, the femoral, and the dorsal artery of the foot, rise at the same instant, and fall at the same point of time.
These facts prove the existence of two great laws not previously enunciated,- 1st, that the heart's beat alternates with the pulse at the wrist; 2ndly, that the pulse of arteries beyond the chest takes place in all parts at the same instant, and without any appreciable interval.
The pulse, it appears, occurs during the retirement of the heart from the thoracic walls, and the collapse or fall of the arteries takes place during the impulse of the heart. During the rise in the handsphygmoscope placed over the arteries, the second sound of the heart has been distinctly heard, and during the fall, the first, softer and more prolonged sound has been easily distinguished.
The horse has been subjected to examination, to learn the relative time of the beat of the heart and arteries, but the respiratory movements and the motions of the animal have hitherto restricted the application of the instruments. However, it has been most distinctly ascertained, by the hand placed upon the heart and upon the plantar artery, that between the beat of these parts there is a decided interval. The slowness of the action of the heart in the horse renders this experiment less open to error than in man. In these experiments upon the horse, Mr. Mavor, the eminent veterinarian, gave his valuable aid.
The sphygmoscope forms a good pneumoscope. It delicately measures the rise and fall of the chest in respiration. It likewise declares the relative duration of inspiration and expiration, and may thus prove useful in the detection of incipient phthisis, and other pulmonary diseases. When the liquid has attained its highest elevation at the end of inspiration, it immediately begins to fall; but when it has reached the lowest point at the end of expiration, it remains there some instants. The ascent is slower than the descent. After the fall of an ordinary expiration, a forced expiration gives a second fall.
The sphygmoscope may be employed without a stand and is then more portable (fig. 3), but from the want of a fixed basis, and from the motion of the ribs on which it must rest, its manifestations are less extensive and satisfactory. It may be maintained in situ with an elastic band placed around the thorax. When em
ployed without a stand, as it must rest upon the ribs, the elastic wall of the chamber should be plain, and not protruding.
The hand-sphygmoscope is an exceedingly delicate instrument, but requires great care and nicety in its construction. It may be made by taking about an inch and a half of a gutta percha tube, half an inch in diameter, slightly widening one extremity of it to make a chamber large enough to hold a small horse-bean, and fastening with thread a piece of thin india-rubber, or of Bourgeaud's india-rubber bandage, securely over it for the elastic and moveable wall. The liquid is now supplied, and the glass tube, with a very fine flat bore, say isth of an inch, and provided with a ring of india-rubber, obtained by cutting off a small portion of a fine india-rubber tube, for a “washer," is now inserted and the instrument is ready for use. The hand-sphygmoscope discovers the blood-wave in regurgitation of the jugular
Portable Sphygmoveins; it responds to the radial of the newly
scope. born infant; it rises and falls with the movements of the brain of the infant, though some months old, as that organ rises and falls under the influence of its arteries. There is no doubt that, applied to the fontanelles before delivery, it will inform the obstetrician whether the fætus be dead or alive, and, in cases of difficult labour, supply important evidence for his guidance.
The hand-sphygmoscope applied to the radial artery, and to the fontanelles of a dying infant three months old, has indicated to the author the influence of respiration upon the circulation. During inspiration, the column of liquid in the tube was found to fall as if sucked down, and during expiration to spring again.
In practical surgery, the hand-sphygmoscope may possibly be employed with advantage, for it will rise with the wave or fluctuation of liquid tumours. It may be placed where the fingers cannot reach. The rise in the instrument is greater in liquid than in aëriform tumours on account of the compressibility of air, and the fall is more rapid and decided when the contents of the tumour are liquid.
For the most part, the hand-sphygmoscope is best applied simply with the aid of the fingers. It is delicately held between the tips of the thumb, fore-and middle-fingers, the nails resting on the examinee. The elastic wall is on no account to be pressed down with a dead weight upon the vessel. It is to be nicely lowered to the level of the artery when collapsed. When the artery rises, it will strike the elastic wall, and as the chamber is fixed by the fingers, the entire blow is communicated to the liquid and it rises in the tube. During the retirement or collapse of the artery, the elastic wall resumes its level condition and draws the liquid down the tube. This motion of the liquid allows the instrument to be employed though the open end of the tube be dependent. When it is desired to avoid the varying pressure experienced when the instrument is held between the fingers, some such apparatus as was invented by Dr. E. S. Blundell, or an elastic band suitably applied around the wrist, will be useful.
The sphygmoscope is for several purposes rendered more convenient of application by interposing, between the chamber and the glass tube, a piece of india-rubber tube of suitable bore and length. In this way the comparison of the beat of the heart and the pulse of an artery is much facilitated, for the glass tubes of the two instruments employed may be brought parallel and close to each other, so that the opposite motions of the liquids in the two tubes are, by near contrast, rendered easier of observation. In employing this adaptation, care must of course be taken that the india-rubber tube is of the same calibre and length in both instruments.
It is hoped that the sphygmoscope will aid in the acquisition of additional knowledge of the movements and condition of the heart, the situation of which within a case of bone, wisely provided to secure it from injury, has this disadvantage for the physiologist and physician, that the action and condition of the organ are with difficulty made out. By means of the sphygmoscope, that small amount of movement which is manisested at the exterior of the chest
be rendered more appreciable to our senses, and more available for physiological and curative purposes ; and perhaps information may be obtained by this instrument which has hitherto been procurable only by the practice of vivisection. Park Street, Grosvenor Square, London,
Jan. 12, 1856.
February 7, 1856.
Colonel SABINE, R.A., V.P. and Treasurer, in the Chair.
The following communications were read :
I. “On the Vitality of the Ova of the Salmonidæ of different
Ages; in a Letter addressed to CHARLES DARWIN, Esq., M.A., V.P.R.S. &c." By John Davy, M.D., F.R.S. Lond. and Edinb. &c. Received January 15, 1856.
MY DEAR SIR,—In a letter which I had the honour to address to you last year
“On the Ova of the Salmon in relation to the distribution of Species," I have expressed the hope that some of the results of observations therein described may aid in solving the question as to the period, the age, at which the impregnated ova of fish are most retentive of life, and consequently are in the state best fitted for transport without loss of life.
Joining with you in considering the subject in need of and deserving further inquiry, I have taken the earliest opportunity that has offered of resuming it. The experiments which I have made, and which I shall now describe, have been more limited than I could have wished, having been confined to the ova of the Charr, as I was not able to obtain the ova of the Salmon or any of its congeners in a fit state for the trials required.
The ova of the Charr which have been the subject of my experiments, were from living fish brought to me from the river Brathay, a tributary of Windermere, on the 9th of November. They were obtained by the pressure of the hand on the abdomen of the females under water, and immediately after their expulsion a portion of liquid milt, procured in the same way from a male, was mixed with them for the purpose of impregnation.
The ova thus treated, 654 in number, procured from two fish, VOL. VIII.
were transferred, after little more than an hour, to a shallow glazed earthenware pan, of a circular form, about a foot in diameter, without gravel, the water in which, afterwards, was changed daily once, and once only. The vessel was kept in a room of a temperature fluctuating from about 55° Fahr. when highest, to about 40° when lowest. The water used was well-water of considerable purity, and before used it was allowed to acquire the temperature of the room.
Two modes occurred to me as likely to afford the means of testing the vital power of the ova, or their power of endurance without loss of vitality; viz. one by subjecting them for a limited time to a temperature raised above the ordinary temperature; the other, by having them conveyed to a considerable distance.
For the trials first proposed, the ova were put into a thin glass vessel half-full of water, which was placed in a water-bath and heated to the temperature desired.
The first experiment was made on ova taken from the general stock one day after their expulsion. Six, for two hours, were exposed to a temperature varying from 79° to 80° of Fahr. The result was, that they became opaque in the course of twenty-four hours, all but one, and that, some days after, underwent the same change, denoting loss of vitality
The second experiment was made on the 10th of November. Six ova were similarly exposed for two hours to a temperature rising gradually from 70° to 78°; the result was similar : on the following day they were all found opaque.
The third experiment was made on the 11th of November. The same number of eggs were exposed for an hour to a temperature , falling from 70° to 69o. Two shortly became opaque ; four retained their transparency during a month, though in reality dead, which was denoted by their bearing no marks of development when seen under the microscope, those ova which retained their vitality being at that time well advanced.
The fourth experiment was made on the 1st of December ; the ova, the same number, were exposed to a temperature rising from 75o to 78° for an hour and twenty-two minutes. Three became opaque, other three retained their transparency and vitality, and in due time were hatched, the first on the 31st of December, the last on the 7th of January