plied to the individual, and not to the name we may have to give to his complaint. His own life constitutes the individual, and all the alterations of that life, therefore, are individual and not general. One person dies in an epidemic, and another recovers, from causes peculiar to these individuals. Only to the charlatan is disease a congeries of symptoms, for every one of which its special drug has been catalogued.

Certain abnormal conditions have now ceased to be regarded as diseases. Mere "ailing" is as natural a process in advancing age as health. "The Diseases of Advanced Life," so ably treated by Dr. Machlachlan, who studied them among the Greenwich pensioners in his charge, might more properly, we fancy, be entitled "The Natural History of Old Age." The natural changes of age only simulate the diseases of a younger period, and even well-marked special diseases once fastened irremediably upon the system lose their distinctive characteristics and become merged in general decay; and this view has been recently corroborated most strikingly by the facts developed in relation to a recent discovery at Vienna.

The now well-known tendency of renal disease and its consequent ill-nutrition to induce chronic or sub-acute inflammations in the encephalon, we can allude to more conveniently in another section of this article.

A great variety of related phenomena from a single cause, varied by individual tendencies, were formerly classed as half a dozen different diseases. The term epilepsy once denoted a special morbid state with convulsions and unconsciousness. We see in it now a condition of disturbed molecular nerve force, such as is likely to occur in any other aggregate of molecules, in which may occur not only the common phenomena of epilepsy, but coma without convulsions, paralysis following convulsions, sudden and transient mania, and peculiar forms of neuralgia; we must therefore cease to give reality to such an affection apart from its phenomena.

Among the new connections in which old symptoms appear, there are two which deserve special mention as trophies of more minute exactness in study, namely, embolus and locomotor ataxia. To Virchow of Berlin we are indebted for a pathological discovery which has cleared up many obscurities.

Minute doses of fibrine, or coagula of blood, called thrombi, become detached from the chambers or valves of the heart, travelling either in small particles or in masses to the smaller arteries, or they may course along the veins back to the heart. To the coagulation of blood in the living vessels, starting from the fact that arrested blood coagulates at the temperature of the body, 98° F., Virchow has developed his theory of the “inflammations of veins" as it was before regarded, and explains many results formerly attributed to "palsy of the heart," "retrocession of gout," "metastasis," "sudden death," etc. To the formation of clot Virchow gave the name of thrombosis. The projection onwards of the clot or thrombus along the vascular system is called embolism, and the whole series of actions is now known specifically as embolus. From this discovery, as it may almost be called, many things before involved in mystery are brought to light and arrange themselves in definite order, enabling us to anticipate the occurrence of other results, and to prevent them.

The ataxie locomotrice, first described by Dr. Duchenne of Boulogne, is the result of a degeneration of the posterior columns of the cord which, after all the discussion, is the main and distinctive seat. Dr. Baillie, however, had proximated the matter in his description of a sort of "paraplegia, from excessive morbid secretion of the cerebro-spinal fluid, which in the erect posture gravitates to the lower part of the sheath" and pressing upon the cord embarrasses the co-ordination of movements. The isolation of the motor columns in this affection harmonizes with an old physiological notion, that these parts had their own vitality and a separate function, being mere commissures or connecting bands: textures limited to such a function may have a lower vitality than others whose functions are more essential, and at the same time a greater tendency to disease than those of higher vitality.

Having stated much that has been learned of late, let us confess to a little ignorance and to a few wants. We do not know why it is that in the two poisons, cholera and diphtheria, both developed on mucous surfaces from the blood, all the salines and water are poured out in the one, and a fatal effusion of fibrine takes place in the other. The cattle plague and

the horse disease are as far removed as possible beyond the reach of cognition or prevention. Do what we will, epidemics must always be anticipated in some form or other, and hygiene can never replace therapeutics. Finally, we are sadly in want of simple and ready means to recognize chemically the urinary morbid products as easily as we now detect sugar and albumen. They are largely connected with changes in health and disease, and chemistry still owes such methods to medicine.

The Sphygmograph. -Our purpose requires no comment upon the pulse. Well studied by the ancients, during the Middle Ages any reliance upon it was generally regarded as a superstition in the category of astrology; "it was doubted if its varieties, as described by Galen, could really be observed or understood." The pulse, however, will always be recognized as the unerring index of a function whose continuance is essential to life. Not only must the heart not cease its action for a single moment, but we are suspicious of the slightest token that it wearies or faints at its work, for the issues of its halting are the issues of life and death. Apart from its immediate connection with the special disorders of this great centre, the pulse has not lost its position as chief among the methods of finding out the working of every portion of our physical machinery. The sense of touch, however, is not only deceptive, but it cannot be taught; no teacher can ever impart to his pupil the experience or knowledge that his own well-educated finger derives from the pulse. The sense of sight, therefore, is not only a much more reliable guide in itself, but it is a far better medium for description and instruction.

Galileo was the first to conceive the idea of recording accurately and visibly the characters of the pulse, and he constructed for the purpose what he called a pulsilogia, which made no impression in its day and left no trace but its name. Vierordt invented a sphygmograph, but it was full of fallacies and of no clinical value. The name of Marey is now exclusively associated with the modern instrument which is made to register the pulse-shock and the wave of the blood column along the arteries.

The sphygmograph is essentially an arrangement of levers

by which the wave as transmitted is increased in apparent size, or rather exaggerated in action, by movements similar to those of a small upon a larger wheel. An ivory pad rests upon the artery, usually that at the wrist, the rush of blood along the vessel lifting the pad perceptibly even to the eye. But however slight the movement, it is sufficiently exaggerated by the levers to procure a distinct tracing of its normal outline and of its every variation. The impulse received by the ivory is transmitted by a long slip of light and flexible wood, at the opposite or free extremity of which is affixed a fine steel point, which we will call the stylus. By a secondary arrangement, a slide, placed at a right angle with the lever and in contact with the stylus, is made to move by mechanical appliances from right to left across its point, so as to give when in motion, to the liftings of the pad and to the movements of the lever and of the stylus, the effect of tracings in free running hand from left to right. The rate at which the slide moves is made to correspond with the time required by each pulse-wave to effect distinctly the whole of its individual tracing, that is, the rate of about four inches in ten seconds. At this rate of speed, each impulse occupies about four tenths of an inch in space upon the slide, and we here premise that the spaces and lengths to be spoken of assume a healthy pulse, without pressure and with the motion of the slide graduated to this rate. We may also state that the instrument as it was left by Marey, like most mechanical appliances requiring practice and skill in manipulation as well as judgment in induction, has usually sunk out of sight as fast as introduced. It had faults and imperfections which speedily destroyed its reputation for reliability, and at last it came to be scarcely mentioned even in medical textbooks. In fact, it had dropped into what seemed to be its natural place as simply a physiological curiosity. The monographs upon its uses, especially that by Dr. Burdon-Sanderson, are more in the nature of scientific treatises than adequate guides to its clinical use.

These considerations were probably what induced Mr. Mahomed, a student of Guy's Hospital, to commence an extended and exclusive study of the subject, and by his improvements in the instrument, accommodating its movements to the feeblest

pulse, and with the advantages of a nearly perfect mechanism, he has been enabled to present, not only a new method, but a new literature of the sphygmograph.

Although a pen actually dipped in ink may be made to do sphygmographic writing upon white paper, the best register is a tracing by the steel point upon smoked paper made portable and permanent by varnish. And if the reader will now attempt to form a mental picture as he goes along with us, we will endeavor to clear up the mystery of the sphygmograph as intelligibly as it can be done without diagrams, at least to give some conception of the simple process by which the heart is made to write out a description of its own ailments at the end of a telegraphic wire a thousand miles away.

The first impulse imparted to the pad by the artery sends the stylus suddenly upwards on the smoked paper, scratching a straight line of about half an inch or less in vertical height. This first up-stroke is called the percussion stroke, and proceeds from the shock received by the blood-column as a solid body, on the bursting open of the aortic valves as the blood leaves the heart for the general circulation,-a shock communicated almost instantaneously to the whole arterial system. In the normal condition this stroke is distinct from the true pulsewave; if confused or identical with it, it becomes a sign of disease. It is the index of a healthy suddenness and force of the heart's contraction, and measures its muscular strength or weakness in acute disease, but it is not a guide as to the relative amount of blood forced into the aorta for distribution. After marking the percussion stroke, the stylus next drops about a tenth of an inch, at a slight distance away from the vertical line and making a very acute angle with it, and its descent is cut short at this point, and sometimes pushed slightly up again, by the distension of the artery by the true tidal wave. Its next fall forms a curve with the concavity downwards. Up to this point the whole tracing is called the percussion wave, from the starting-point of the percussion stroke to the end of the first curve; and the space between the vertical line and the next regular ascent of the stylus measures the time elapsing between the opening of the aortic valves and the arrival at the wrist (of the tidal impulse). Next follows the