These are cases of severe hysteria wherein consciousness rests upon a profound stage of dreaming. The nature of the attack and the stability of the hallucination alone show a certain kinship with our case, which in this respect has numerous analogies with the corresponding states of hysteria. For instance, with those cases where a psychical shock (rape, etc.) was the occasion for the outbreak of hysterical attacks, and where at times the original incident is lived over again, stereotyped in the hallucination. But our case gets its specific mould from the identity of the consciousness in the different attacks. It is an "Etat Second" with its own memory and separated from the waking state by complete amnesia. This differentiates it from the above-mentioned twilight states and links it to the so-called somnambulic conditions. Charcot[5] divides the somnambulic states into two chief classes:-- 1. Delirium with well-marked incoordination of representation and action. 2. Delirium with co-ordinated action. This approaches the waking state. Our case belongs to the latter class. If by somnambulism be understood a state of systematised partial waking,[6] any critical review of this affection must take account of those exceptional cases of recurrent amnesias which have been observed now and again. These, apart from nocturnal ambulism, are the simplest conditions of systematised partial waking. Naef's case is certainly the most remarkable in the literature. It deals with a gentleman of 32, with a very bad family history presenting numerous signs of degeneration, partly functional, partly organic. In consequence of over-work at the age of 17 he had a peculiar twilight state with delusions, which lasted some days and was cured with a sudden recovery of memory. Later he was subject to frequent attacks of giddiness and palpitation of the heart and vomiting; but these attacks were never attended by loss of consciousness. At the termination of some feverish illness he suddenly travelled from Australia to Zürich, where he lived for some weeks in careless cheerfulness, and only came to himself when he read in the paper of his sudden disappearance from Australia. He had a total and retrograde amnesia for the several months which included the journey to Australia, his sojourn there and the return journey. Azam[7] has published a case of periodic amnesia. Albert X., 12 1/2 years old, of hysterical disposition, was several times attacked in the course of a few years by conditions of amnesia in which he forgot reading, writing and arithmetic, even at times his own language, for several weeks at a stretch. The intervals were normal.