There is usually little difficulty in the discrimination of hysterical stupor. Occasionally it shows, superficially, a similarity to the manic-depressive type. Fundamentally, there is a wide divergence between the two processes, in that in the hysterical form a dissociation of consciousness takes place, the patient living in a reminiscent, imaginary or artificially suggested environment, while in a true stupor there is a withdrawal of interest as a whole and a consequent diffuse reduction of all mental processes. This difference is sooner or later manifested by the appearance in the hysteric of conduct or speech embodying definite and elaborated ideas. As has been stated fully in the last chapter (to which the reader is referred), the stupor of dementia præcox is to be differentiated from that of manic-depressive insanity by the inconsistency of the symptoms in the former and the appearance of dementia præcox features during the stupor, such as inappropriate affect, giggling, or scattering. Further, the nature of the disorder is usually manifest before the onset of the stupor as such. Sometimes very puzzling cases occur in more advanced years when it is difficult to say whether one is dealing with involution melancholia or stupor. Such patients show inactivity, considerable apathy and wetting and soiling, and with these a whining hypochondria, negativism, and often a rather mawkish sentimental death content without the dramatic anxiety which usually characterizes the involution state. In these cases the diagnosis is bound to be a matter of taste. In our opinion it is probably better to regard these as clinically impure types. They may be looked on as, fundamentally, involution melancholias (the course of the disease is protracted, if not chronic) in whom the regressive process characteristic of stupor is present as well as that of involution. Great difficulties are also met with in the manic-depressive group proper. So often a stupor begins with the same indefinite kind of upset as does another psychosis that the development may furnish no clew. Any condition where there is inactivity, scanty verbal productivity and poor intellectual performance resembles stupor. This triad of symptoms occurs in retarded depressions, in absorbed manic states and in perplexities. Negativism and catalepsy are never well developed except in stupor. So if these symptoms be present the diagnosis is simplified. But they are often absent from a typical stupor. Let us consider these three groups separately.