times before any inspiration intervenes brings on dyspnoea in a child, with the convulsive effort attendant thereon; and at the same time it brings on the spasmodic reflex action of the laryngeal muscles which narrow the glottis, so as to produce a falsetto, or crowing, or whooping note as protracted as the relieving inspiration itself. The non-development of the posterior glottidean space in infancy is the anatomical basis of this. It is to be kept in mind that the inspiration of infants may be crowing where there is no cough; and that in paroxysms of whooping-cough itself, the deep indraught that ends the paroxysm may have the whistling or whooping character less marked as the child is farther from its first childhood.

It is certainly a very remarkable thing that a grown person who has caught the infection in a house where there is whooping-cough among the children, should sometimes whoop like them. Whooping in an adult is a ludicrous anachronism; and in the rare cases where it occurs, it betrays some peculiar tendency to mimesis. I should be inclined to say that the mimicry in such cases is more like the contagious mimicry of chorea or hysteria, conveyed by the ear and eye, than any part of the true mimetic effect which belongs to the contagious particles of the catarrhal disease.*

Whooping-cough, then, is the distinctive postcatarrhal cough of young children, the memory of

* Sturges ('Med. Times,' ii, 1885, p. 6) entertains the question whether a good deal of the whooping of children in an epidemic may not be due to subjective mimicry (a form of the idée fixe), and quotes Bouchut in support of that view.

expulsive reflex acts continuing for a considerable time out of all proportion to the local irritation, recurring at intervals and especially during the more exhausted hours of sleep, and in those periodical recurrences assuming a paroxysmal or convulsive character much more distressing than the cough which has the presence of a real irritant in the air-passages for its cause and the expulsion of the irritant for its object. A cough of that kind is "often kept up by custom," acting on a debilitated or irritable state of body, as Dr. Anthony Thomson admits; or, as Sir Thomas Watson says, "the cough would almost seem to be kept up by the mere influence of habit." But if we are to do full justice to the principle of unconscious memory inhering in nervous reflex mechanisms, we shall make the whole of the paroxysmal or whooping stage an affair of habit, or, in other words, ascribe all the coughing that goes on after the initial or acute catarrh has subsided to a memory of the catarrhal irritation.

This memory-doctrine of whooping-cough leaves us with several things still to explain. In the first place we have to account for the fact that paroxysmal or convulsive cough is a much more common sequel of catarrh in children than in adults; secondly, we have to explain why whooping-cough is so inveterate, and why it has in general so remarkable a conformity of type as to be counted among the specific diseases; and, thirdly, there is the stubborn fact that children seldom have it twice. All these difficulties in the way

of the memory-doctrine find a solution by keeping steadily in mind the physiological peculiarities of childhood in general, as well as the particular circumstances that favour the occurrence of whooping-cough in individual children.

As regards the frequency of paroxysmal or whooping-cough in children after a coryza or other catarrh of the respiratory organs, it may be said that the age of childhood has a tenacious memory for reflex effects in general. In the first year or two of life, nearly all the combinations or associations that a child holds in its body and mind are unconscious memories, of the instinctive, automatic, and reflex sort. A fortnight's bronchial, laryngeal or nasal irritation has an opportunity then of making an impression on the reflex nerve-mechanisms which it will never have again. As the intelligence and the will develop, the province of unconscious memories and of reflex, automatic, and instinctive actions becomes restricted. Mr. Herbert Spencer maintains that the memory (that is to say, conscious memory) and the will do in fact arise out of automatic actions, as these tend to "become complex, infrequent, and hesitating." Unconscious memories have the field almost entirely to themselves in infancy or early childhood. Is it surprising, then, that the coughing reflexes of a feverish cold should be so uniformly remembered at that time of life? Even in adults, as we have seen, a post-catarrhal cough, apt to come on in distressing paroxysms, is not altogether

rare.

The second point concerns the so-called specific characters of whooping-cough, its conformity of type and its natural history characters in general, wherein the paroxysmal cough of children may seem to differ toto cœlo from that of adults. I have already spoken of the peculiar whooping indraught of the breath, which is really a minor point in the natural history, although it gives the disease its name. Much more distinctive features of the malady are its inveteracy, or almost prescribed course and duration, the somewhat regular intervals between the paroxysms, and their peculiar severity.

The opinion has already been quoted from Cohnheim that the intensity of the coughing paroxysms is out of all proportion to any local irritation at the time; in fact, there is probably no such local irritation at all, for the child (except where the violence of coughing has itself had serious after-effects in the lungs and brain) is remarkably well and comfortable in the intervals. Why, then, are the paroxysms so explosive in their periodical occurrence and so intense while they last? We shall find an explanation if we go to another principle or nervous action, which is a further development of the law of unconscious memory. I shall give it as stated by Rindfleisch.

There are two great distinguishing marks of nervous symptoms in disease: firstly, their periodicity or intermitting character; and secondly, the apparent disproportion between the intensity of the manifestations and the cause of them. The periodicity is based on

the general biological principle of labour and fatigue, of waking and sleeping, of force spent and force recovered. The apparent inadequacy of the cause to the effect arises out of a property of the central nervous system to absorb enormous quantities of ingoing excitations as if they left no trace, while in reality it stores them up in the form of potential energy. Thus it is possible for some one impression which may hardly exceed the limits of physiological excitation, but is aided by circumstances, suddenly to let loose the whole store of accumulated forces and to give rise to an outbreak of the most intense feelings and most powerful movements.*

Applying this law to the paroxysms of whoopingcough (an application which Professor Rindfleisch finds no occasion to make, inasmuch as he refers the disease and all its phenomena to the specific action of an invading parasite), we shall take it that the irritations of the respiratory mucous membrane, in the acute catarrhal stage, are only in part answered at the time by the coughing reflex act; many of them are stored up as unconscious memories of which an account will one day be given. We may represent them to the mind crudely as so many suppressed coughs. Now, there are no doubt circumstances where this want of outlet, response, or expression at the time is especially apt to occur; and these are peculiarly the circumstances of whooping-cough.

The period of infancy is in itself an occasion

* Elemente der Pathologie,' Leipzig, 1883, p. 121.,

n;