CtionnA is essentially a disease of the second for although it is occasionally met with in children under five years of age, and sometimes even in adults, yet an enormous majority of the cases are found between the ages of five and fifteen years.
Causation.—Children who are likely to be attacked by this complaint are those in whose family there is a tendency to neurotic disease, and who, perhaps as a consequence of this tendency, are born delicate and sensitive, with a highly impressionable nervous system. Perhaps the mother may herself in childhood have been afflicted in the same way. Girls are much more prone to it than boys, and a child who has once passed through an attack is very likely to suffer from it a second time.
The outbreak of the disorder may be determined by an attack of rheumatism, or by some shock to the nervous system, as a fright, or by any cause which reduces the strength more or less suddenly and sets up anaemia or some cachectic condition. There is an indisputable connection between rheumatism and chorea. It is common to find a family history of rheumatic attacks. Often the patient has herself suffered from it, either in its acute or subacute form. Out of forty-two cases (nine boys and thirty-three girls) of whom I have notes, I find distinct history of rheumatic attacks in sixteen. Others came of rheumatic families, although it could not be discovered that they had suffered from the disease themselves. There was a heart-murmur in twenty-seven, and in many cases the rheu matic disease had left evident traces of its passage in a harsh cardiac murmur with some hypertrophy of the heart. Still, there is no doubt that we find many cases of chorea in which no history of rheumatism can be discovered, and many rheumatic children never have chorea. Rheuma tism alone will not set up the complaint, for a peculiar instability of the nervous system is no doubt essential to the production of the disorder. Rilliet states that in Geneva, where rheumatism was a common disease, chorea was almost unknown, and according to the investigations of Dr. Weir Mitchell, it appears that amongst negro children, in whom rheu matism is not uncommon, chorea is very rarely seen.
Dr. Anstie was of opinion that the hereditary rheumatic tendency was associated with a hereditary tendency to neurotic diseases of various kinds, and especially to chorea. In support of this view he instanced the case of nine families with decided rheumatic history. In each of these several of the children had suffered from rheumatism, to his own personal knowledge. In all of them, also, there was a strong neurotic inheritance, which showed itself in many cases in the form of chorea. The striking fact consisted in this, that although many children suffered from rheu matism and many from chorea, it was not the victims of rheumatism who were especially prone to chorea. As often as not those children who had suffered from rheumatism escaped the neurosis, while others who had never had rheumatism fell victims to chorea.
Other conditions appear to influence the incidence of the disease. The rarity of chorea amongst the little negroes seems to show that the degree of cerebral development may constitute an important element in the ten dency to the disorder ; for the brain in the black race is no doubt less perfectly developed than it is in whites. Again, monotony of life and ab sence of mental excitement must tend to impart immunity from chorea, for Dr. Weir Mitchell's researches show that the disease is far less common in rural districts than it is in towns, and in small towns than in large cities.
In a suitable subject any irritant may set up the complaint. Worms in the intestinal canal, and, of course, the practice of masturbation, have been cited as frequent causes of this as of all other nervous disorders. Still, I cannot but think that the influence of the two causes just mentioned, of masturbation especially, in provoking nervous derangements in the child has been greatly exaggerated. Chorea is sometimes associated with grave diseases of the nervous centres. It has been seen in connection with cere bral tubercle, cerebral hypertrophy, and softening of the brain ; and Dr. Jacoby has reported a case in which violent choreic movements were in duced by meningitis involving the membranes of the cervical part of the spinal cord.