ETIOLOGY.--It is certain that the same causes that produce spasm in childhood are efficient in the adult, though there is an absence of some of the conditions that render the disease so frequent in infancy. The cartilages have become more firm, and consequently are not so easily moved by the action of the constrictor of the vestibule of the glottis; the size of the cavity in proportion to the necessities of the body for air is larger; the control of the voluntary over the automatic actions of the muscles of mixed function is greater; the reflex irritability of the nervous apparatus is less. These facts all render the probability of spasm in the adult much less than in the child. On the other hand, the development of the generative organs, and the widespread influence which they have upon the respiratory and circulatory as well as upon the central nervous system, introduces a new factor as a cause of motor disturbances of the larynx. This new element is a reason for the fact that in adults the predisposing influence of sex is reversed: after puberty the disease occurs more frequently among females than among males. The hysterical character of many of these cases may be inferred from this preponderance of one sex over the other among the subjects attacked. This fact has been seen and described by Charcot, Lefferts, and others. Irritation along the track of the nerves, morbid conditions of the mucous surfaces, or muscular irritability, may be each a cause of spasm. SYMPTOMS.--The symptomatology of spasm in the adult does not differ in any material respect from the phenomena observed in children. It is in the rarity and the comparatively milder character of these symptoms that the difference is to be found. The attacks occur at night, as in children, but, so far as I have observed them, they may also take place during the day. When very severe they occasion great alarm to the patient, and for this reason {75} produce a profound impression, not only upon the physical, but also upon the mental and emotional, state. The duration and termination of the affection are about the same as in children. In the mortality-tables we find every year a certain number of deaths from spasm of the larynx in adults. It is probable that among these there are quite a number which should be placed elsewhere. A patient may die from spasm of the larynx, which spasm is produced by an ulceration, by a tumor, by the presence of a foreign body in the organ. As in children it is quite certain that the deaths reported as from spasm of the larynx include many that should be referred to central or other diseases, so here the immediate cause of death is not unfrequently given instead of the real and essential cause. This fact makes it difficult to reach anything like a definite conclusion as to the termination of the disease; only this can be said: the great majority of cases recover.