That failure of appetite for, and curiosity about, new things, which is already marked in the preceding stage, becomes more and more distinct. That deadening of the sensibility, which expresses the complete saturation of the elements of the sensorium and their incapacity for maintaining a condition of erethism, takes more and more significant forms. The human brain experiences the need of prolonged repose ; the ardour of the grand struggle for life becomes painful to it. A retreat is sounded from a great number of social careers. Thus it is that that period of inactivity which inevitably awaits each individual, as regards the social part he has played, physiologically expresses the slow and gradual wearing out of the energies of automatic life, which by degrees cease to vibrate, and betray by their slacken ing the progressive dulling of the sensibility of the cerebral cell.
In proportion, then, as sensibility grows languid, and the faculty of erethism loses its energy in the elements of the sensoriunz, the external manifestations of the life of the brain undergo a parallel retrogressive movement. Repose and silence insensibly invade them. The field of
the ideas and sentiments grows narrower ; intellectual spontaneity becomes languid, and verbal expression, and conversation, dried up at the fountain-head, cease to be interesting and endowed with a spontaneous character. The man who has nothing to say, who has but a few notes of his personality to set vibrating, speaks no more or says but little, at least if we do not take for original conversation those vapid phrases that men think them selves obliged to exchange, when they are in each other's company, and of which the inanity, to some extent reflex, only covers the absence of ideas and sentiments.
Thus it is that, through the necessary connections which unite all the zones of cerebral activity, the mani festations of senility by degrees gain ground in the psycho-intellectual spheres. The mere fact that there are regions of the brain which have primarily been struck with stupor and histological degeneration, causes the same retrogressive processes to radiate to a distance, and, through secondary lesions, inevitably to produce the symptoms of senility and more or less progressive dementia,