A fourth degree of somnambulism is marked by the disappearance of consciousness, intellect, sensibility, and the power of motion. Only the lower functions of organic life remain. The patient merely lives, he neither thinks nor acts. This constitutes the state of somnambulic lethargy, a condition which differs from deep sleep only in the fact that under the influence of external impulses or of partial awaking it may easily pass into the second form of the affection, the somnambulic dream. Such is the classification of MM. Ball and Chambard. It possesses the merit of great precision and clearness. If the warning which its authors themselves utter against its too literal acceptance be respected, it will be found to afford a very convenient explanation of the manner in which the various degrees of somnambulism are reached. But it must be remembered that between these pronounced and definite forms exist a great number of intermediate degrees. Partial revivals and temporary resurrections of the higher faculties of the mind may intrude themselves among the activities which depend upon lower functions; as, for example, when the ordinary unconsciousness of lethargy is briefly interrupted by an event which may remain permanently fixed in memory after waking, even though all other concurrent incidents were unnoticed and left no trace behind. Keeping this caution in mind, the following diagram will be found useful: +=======================================================================+ | |Organic|Sensibility:|Imaginative|Coördinative|Consciousness| | | Life | Motion | Faculties:| Faculties:| | | | | | Memory, | Judgment, | | | | | |Imagination| Attention, | | | | | | | Volition | | |-----------|-----------------------------------------------------------| |Normal life|XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX | |-----------|-----------------------------------------------------------| |Somnambulic| | | life |XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX | |-----------|-----------------------------------------------------------| |Somnambulic| | | dream |XXXXXXXXXXXXXXXXXXXXXXXXXX | |-----------|-----------------------------------------------------------| |Somnambulic| | | automatism|XXXXXXXXXXXXXX | |-----------|-----------------------------------------------------------| |Somnambulic| | | lethargy |XX |