it was inevitable that we should ere long hear of a neurotic theory of rheumatism. Such a theory was indeed suggested by the elder Dr. Mitchell, but the suggestion lay dormant till increasing knowledge of the subject to which he drew attention, the occurrence of joint troubles as a sequence of nerve lesions, combined with the result of the separate study of the pathology of rheumatoid arthritis, led to its revival.
This theory has assumed two forms.
By most of those who advocate it the disturbance of the nerve centres which originates the joint troubles is believed to be produced by peripheral irritation applied to the surface nerves, and trans mitted by them to the nutrition centres of the joints. That joint troubles might thus be induced there can be no doubt; but that acute rheumatism could be so caused seems to me highly improbable. For in the first place acute inflammation such as that which characterizes the joint affection of that disease is not the form of joint trouble which we find associated with lesions of nerves and nerve centres. Nor can it be regarded as a priori other than highly improbable that such acute sthenic inflammation should be the result of malnutri tion. And, in the second place, inflammation of the joints is not the only thing with which we have to deal in acute rheumatism. The disease has other features and other phenomena calling for explana tion as much as do the joint lesions. If, for instance, as is main tained, cold be the common cause of the peripheral nerve irritation which sets the malady agoing, why is the disease more common in temperate than in cold climates? Why is it most common at the age at which the power of resisting cold is greatest, fifteen to fifty? And why so rare among children and older people whose power of resisting cold is so much less? Again, how on this view are we to explain the invasion of fresh joints after the patient has been warm in bed for days, maybe for weeks? How account for the occurrence of endocarditis and pericarditis? Why is the endocarditis so limited in extent? Why does it affect only the valves of the left side, and only one surface of the valve? How account for the excess of lactic acid in the system? These are all points of which an explanation must be given ; and no theory of rheumatism can be regarded as satisfactory which does not do so. But the neurotic theory takes no cognizance of the heart trouble, and offers of the joint inflammation an explanation which fails to deal with some of the characteristic features of that lesion.
The fact is that the phenomena of acute rheumatism are such as can be explained on no view which does not recognize the action of a poison which is produced in the system during the course of the malady and circulates in the blood. Recognizing this, Dr. Latham, one of the most strenuous advocates of the neurotic theory, advanced the view that as a result of exposure to cold there is produced a lay perfemic state of the muscles, that from this there results an increased formation of glycocin, that this is ultimately transformed in the liver into uric acid, and that this uric acid it is which by impairing the action of the nutrition centres of the joints causes the inflamma tion noted in acute rheumatism. According to this view uric acid
with some aid from lactic acid causes rheumatism much as it causes gout.
The objections to this very ingenious theory are, first, all those which have been already advanced against the original form of the neurotic theory—and, second, the fact which has been demonstrated by Garrod and others over and over again, that uric acid does not exist in excess in the blood in acute rheumatism. It is an acid which when it exists is very easily detected. According to Dr. Latham's hypothesis it ought to be there; but it really is not.
It may be laid down as a general rule in science that when we have to advance several hypotheses to explain one set of phenomena we are almost certainly on the wrong tack. Dr. Latham's theory of the mode of production of acute rheumatism with hypotheses. The ability with which he manipulates them does not remove the weakness and inherent improbability imparted to his theory by their number, and the absence of facts to support them.
Of all acute febrile ailments acute rheumatism is the one in which the nervous centres give least evidence of disturbance. In typhus and typhoid fevers, scarlet fever, pneumonia, etc., there are gener ally symptoms distinctly and directly referable to disturbance of the brain. In rheumatic fever such symptoms seldom occur except in cases of hyperpyrexia and in cases complicated with acute carditis or pericarditis, and in them the nervous symptoms are due to special causes, and have no connection with the joint troubles.
Neither the natural history nor the clinical features of acute rheu matism support the view that the disease is of neurotic origin. As Arnozan remarks, "Avant de prononcer que les lesions articulaires du rhumatisme sont des lesions trophiques dependant de la moelle, it faudrait demontrer d'abord que celle-ci est reellethent atteinte." Pathological analogies have been inferred between gout, rheuma tism, rheumatoid arthritis, and spurious arthritis because the joints are affected in each; but the analogies are really clinical, and we must be careful to distinguish between clinical and pathological anal ogy, or we shall fall into pathological error.
The joint troubles referred to represent four different ailments as distinct in their pathological histories as are pneumonia, bronchitis, asthma, and pulmonary emphysema. Because these ailments consist each in some form of pulmonary trouble we do not infer pathological analogies between them, or refer each to disorder of the respiratory centre. Though we look upon asthma as a disease of the nervous system, we do not say that bronchitis is so too. During an attack of either ailment the calibre of the bronchial tubes is diminished, and their functional utility interfered with, but we do not allow such clinical analogies to blind us to the fact that the two ailments have no pathological affinity. The joint troubles which result from nerve lesions bear to acute rheumatism no closer resemblance either clini cally or pathologically than asthma does to acute bronchitis; and a careful consideration of all the evidence leads us to indorse Arno zan's conclusion that " les rapports eutre le systeme nervwx et le rhumatisme articulaire sont encore a trouver."