life. A much more local disruption of connection, limited perhaps to the cortex, might be sufficient to explain the subjective condition in sleep. At any rate, Duval's view is that the cortical cells are capable of retracting or extending their processes so as to sever and resume their relation with neighboring elements. Experimental evidence in support of this theory is naturally slight. Wiedersheim has described amœboid movements on the part of cells in the nervous system of a small transparent crab. Of course it is only in such lower forms that the living cells can readily be brought under the microscope. Duval himself suddenly beheaded dogs that were awake and others in anæsthesia and made histological preparations from the brains. He believed he could distinguish the sleeping brain by the more contracted and isolated appearance of its cells.
The second histological theory of sleep, which has been said to be quite opposed to the first, is that of the Italian neurologist, Lugaro. Both demand the capability of amœboid movement on the part of the cells. But while Duval supposes that in sleep the cells have broken their contacts, Lugaro supposes that they have made new contacts with great freedom. At first thought this view seems unreasonable. A multiplicity of contacts and added pathways in the brain might be supposed to imply a richer and keener consciousness. But this would be true only to a certain point. When the indiscriminate combination had gone a step further mental confusion might be expected, then fantastic associations and a meaningless mosaic of memories—practically a state of dreaming. Let the cells commingle their impulses still more freely and consciousness will be lost, for the diffusion of energy in the brain will result in a lessened intensity of flow in the principal channels. If each cell scatters its communications in every possible direction no definite effect in consciousness is to be looked for. According to Duval, the cells which are affected in sleep can not discharge; according to Lugaro, they may do so, but the resulting impulses are utterly dissipated in a maze of by-ways. Waking, according to Duval, is the resumption of intercourse among these cells; according to Lugaro, it is the restriction of intercourse to habitual and purposeful channels.
There is no reason why we may not be eclectic in regard to these two points of view. It may be that many paths are interrupted in sleep, while others are opened. In the hypnotic state it is clear that many paths are blocked, including those by which the will of the subject habitually asserts itself, while others, especially those making connections between the auditory and motor areas, transmit impulses with extraordinary efficiency. This condition is explicable if we suppose that certain synapses are broken, as Duval imagines, and that
