and leucocyte count in response to exercise is that the rise in patient and control are identical, if the exercise is sufficient to produce in patient and control the same degree of respiratory distress."
In short these patients responded to stimuli in an excessive man- ner. The first method of dealing with them was an attempt to sort them out by means of graduated exercises and for this purpose an instructor was obtained^ It was soon found that capacity varied a good deal but that it could be increased in certain instances by a judicious use of the exercises. It was soon discovered that the pre- dominant etiological factor in the clinical histories of the cases was infection of one kind or another. In 558 patients the history of onset was definitely dated from rheumatic fever or chorea in 68 instances (or 12%), from dysentery in 14 instances, from typhoid fever and diarrhoea in 14 instances, from pneumonia, pleurisy and bronchitis in 25 instances, from pyrexia of unknown origin (trench fever in all probability) in 28, and from miscellaneous infections such as diph- theria, scarlet fever, syphilis and pus infections in 30 instances. In all these the first symptoms of the malady were definitely noticed during convalescence from the disease in question. The percentage covered is thus 33. But this by no means exhausts the importance of infection, for of the 376 cases which remain there was a history of rheumatic fever in 57 cases, of repeated joint pains in 8 cases, and of pleurisy, pneumonia, syphilis and other maladies in many more. Moreover, any intercurrent infection always had the effect of greatly increasing the severity of the symptoms. Further work in other hospitals has only increased the tendency to regard this malady as an extra-cardial one and to assign its cause to infection or, in a few instances, to gastro-intestinal troubles, shock and so on.
That irritable heart or " nervous heart " is found in civilian practice is certain, and that it constitutes a large proportion of so- called heart disease cases is equally beyond doubt. That it is not heart disease at all is becoming increasingly evident. Indeed the vital and even revolutionary part of this work lies in the fact that symptoms which have been associated with one kind of mechanism of origin are now seen to be capable of production by another kind of mechanism. I n other words, breathlessness on exertion and cardiac pain may occur in the absence of any damage to the heart.
Thus it became necessary to re-investigate these symptoms. Numerous attempts have been and are being made. At one period, about 1919, a chemical theory held first place in interest. It was suggested that breathlessness was due to a lack of " buffer " salts in the blood. The idea was that the blood contains various salts and notably acid phosphate of soda, which are capable of absorbing either an excess of acid or of alkali. Thus the action of the buffer salt is comparable to that of a sponge. It was suggested that these cases of nervous heart were deficient in buffer salts and so lacked the means of preventing alterations in blood quality. This view was supported by a great deal of very delicate work but it has scarcely found general acceptance. An alternative view has recently been suggested to the effect that the blood lacks oxygen. It is pointed out that a general condition of venous stasis exists and that on this account a smaller quantity of blood passes through the lungs in a given time. The oxygen intake is lowered. In consequence during effort there is no great reserve of oxygen for use in the muscles and so more rapid and forcible breathing is rendered necessary in order to increase the supply. The stimulus here is not an excess of waste products but a lack of oxygen. Curiously enough there appears to be some ground for supposing that oxygen want is not in any sense synonymous with excess of carbonic acid gas. In the absence of sufficient oxygen the blood does not become less but rather tends to become more alkaline. This subject, however, is at present being further investigated. The researches of Haldane of Oxford and Barcroft of Cambridge must be mentioned in connexion with it.
The oxygen want is probably secondary to a nervous disturbance whereby the circulation is upset. In fact the evidence available at present points to an effect of the toxins of disease on the nervous system, and more especially on the involuntary nervous system. This system regulates the action of the heart and also the tone of the circulation. The smaller arteries are under its control and recent work, following that of Roy, suggests that even the capillaries may be supplied with nerves. It is, moreover, related in an intimate way to certain of the ductless glands and notably the supra-renals which produce adrenalin. The work of Gaskell has furnished a new con- ception of this system and it is now possible to recognize two main branches the true sympathetic, the action of which on the heart is accelerator, and the vago-sacral sympathetic or parasympathetic, the action of which on the heart is inhibitor. It can easily be seen that any disturbance of the relationship existing between these branches of the involuntary nervous system must react not only on the efficiency of the heart and of its responses to calls for increased effort but on the integrity of the whole circulatory tree. In point of fact the tendency to stasis or stagnation in many " nervous heart " cases is explicable only in terms of this nervous system.
In the same manner the origin of " cardiac " pain in these cases is probably to be related to the nervous system. How exactly the pain arises still remains in dispute. Enough that the pain is often excited by effort and tends to diminish if effort is abandoned. The fact that it usually disappears if the auricles of the heart begin to fibrillate has suggested to some workers that distention of those chambers by blood may act as the exciting cause.
The fact of immediate importance is that breathlessness, pain, palpitation, giddiness, exhaustion and the other symptoms of this series cannot be taken as of themselves indicating heart failure. They may all be present and yet the heart may be active and sound. Cardiologists have thus been compelled to reconsider the evidence on which a grave prognosis may be founded and have come to appreciate the great difficulties which beset their paths. Indeed the tendency has become apparent to regard serious heart mischief in a patient showing symptoms of the kind mentioned as the exception rather than the rule.
Nevertheless certain guides are available which should enable a reasonable opinion to be formed. If for example a patient has been suffering from a degree of limitation of the field of effort for a con- siderable period and if this degree is not exceeded it can be inferred that, whatever injurious agent is present, whether it be organic disease or a poison, the mischief is stationary. There is no " failure " in the true significance of that term. If moreover a sharp restriction of the field of effort is accompanied by signs of febrile illness and if the restriction is removed as the fever subsides a grave view need not be taken. But if a marked restriction occurs without evident cause this points in all probability to a weakening of the heart muscle. Again if dilation of the organ takes place and is progressive, or if auricular fibrillation supervenes, heart failure may be confident- ly diagnosed. In the last issue heart failure would seem to be always a muscle problem. The ultimate importance of extra- cardial factors is thus their influence on the burden which the heart is called upon to support. The heavier that burden and the weaker the organ (e.g. on account of organic disease) the earlier may failure be expected to show itself.
Heart Flutter. The most recent contribution to the study of heart disease is that of Dr. Thomas Lewis on the nature of auricular flutter and auricular fibrillation. Lewis followed the experiments of Mayer in 1908 and of Mines in 1913. These workers used the contractile bell of the jellyfish and later rings of muscle cut from the ventricles of turtles and the auricles of tele- ostean fishes. The experiments were repeated in 1914 by Mines and Garvey.on rings of muscle cut from the ventricles of the dog.
The experiments were as follow: If a ring of muscle was stimu- lated at a given point in its circumference by means of a single shock, a wave of excitation is set up. This wave develops two "crests"; one goes round the ring in one direction, the other in the other direction. Necessarily they meet at a point. The whole ring has now become involved by the wave and has passed into a state of excitation. It has become " refractory," that is to say that for the moment it is no longer excitable by further shocks.
When therefore the waves of excitation meet one another on the circumference of the ring, movement is brought to an end. In Lewis's words: " like two waves of flame, two waves of excitation meeting do not override: each crest forms an impassable barrier."
The ring of muscle remains in this state of excitation (which is nearly though not quite synchronous with the state of contraction) for a period and then recovers. It recovers in the order in which it has become involved, that is to say it begins to be " responsive " again at the spot where the primary shock was applied. The re- sponsiveness travels round the ring in two waves just as the ex- citability did. When the crests of these second waves meet the ring has returned to its original condition. It is wholly responsive.
Lewis uses the analogy of a prairie fire which can spread only in those directions in which unburnt grass awaits it. If, therefore, for any reason a portion of the ring of muscle happens to be " refrac- tory " or in a state of excitability when a fresh shock is given only one wave of excitability may be able to travel. The fire, so to speak, is stopped by a patch of outburnt grass. Recovery of this refractory area may, however, have taken place before the new wave gets round to it. In that case the wave will continue to circulate, for when it returns to its starting point that starting point will have recovered its responsiveness. It is, indeed, as if the grass had grown again on the face of the prairie by the time the fire got back to it.
This curious condition of affairs is spoken of as a " circus move- ment " and it is in these circus movements that this investigator believes he has discovered the secret of auricular flutter and auri- cular fibrillation. For some reason the normal wave of excitability which should pass over the muscle of the heart is replaced by a wave travelling in a circle over the surface of the auricle. This wave fol- lows, it would appear, the same circular path which it has mapped out for itself and then returns again to its starting point. Here it meets muscle which has so far recovered as to be responsive once more, and thus the wave keeps on travelling round and round. Subsidiary waves are sent out, like tributary tongues of fire, over the muscular surface and the auricle beats at the rapid rate which is characteristic of the clinical condition.
Lewis has been able to induce fluttering of the auricles experi- mentally in dogs and has been able to prove that this is the same condition as that encountered in the human subject. " Flutter," he declares, " consists essentially of a continuously circulating wave." The path taken by this wave is not always the same for each animal. In the dog an artificial flutter may last for hours; in man flutter may
