ETIOLOGY.--So far as we know, there are no predisposing causes. The chief exciting cause of this affection is unquestionably diphtheria. It is, in fact, a sequel of diphtheria. It will hardly be necessary to repeat here what the reader will find fully discussed in the sections devoted to diphtheritic inflammation of the fauces and adjacent parts: we are mainly concerned with the phenomena. Just how this morbid process produces paralysis is not known. It is believed by some observers that the disease is produced by the alteration of the nutrition of the parts during the progress of the diphtheria. It is stated that the parts most nearly related to the seat of the exudation are most likely to become involved. This is thought to sustain the theory of the direct propagation of the morbid changes from the mucous surfaces to the nerves and muscles. That the paralysis following diphtheria is not, however, produced alone in this manner seems to be made evident by the fact that distant parts, parts which have not been at all involved in the disease, do nevertheless become affected with paralysis. This paralysis develops when the general health and the nutritive changes are all improving. It is quite evident, therefore, that the loss of power in the laryngeal muscles, as well as the altered sensibility, in part at least, must be due to some lesion of the nerve-centres. In addition to the causes above noted, anything which impairs or destroys the function of the superior laryngeal nerve may produce this affection. In the anæsthesia from hysteria we know only the fact, but do not know just how the derangements of the nerves in a distant part, or in the nerve-centres perhaps, are so reflected as to change the function of this organ. The hyperæsthesias, the paræsthesias, and the anæsthesias of hysterical character are all probably produced in the same manner. Anæsthesia in bulbar paralysis is easily understood, but need not, for the reasons already given, engage our attention.