6. By their wearing warmer clothes, and preferring warmer rooms, than in the former periods of their lives. This practice is so uniform, that it would not be difficult, in many cases, to tell a man's age by his dress, or by finding out at what degree of heat he found himself comfortable in a close room.
7. By dreams. These are universal among old people. They arise from their short and imperfect sleep.
8. It has been often said, that “We are once men, and twice children.” In speaking of the state of animal life in infancy, I remarked that the contractility of the animal fibres predominated over their sensibility in that stage of life. The same thing takes place in old people, and it is in consequence of the return of this infantile state of the system, that all the stimuli which have been mentioned act upon them with much more force than in middle life. This sameness, in the predominance of excitability over sensibility in children and old people, will account for the similarity of their habits with respect to eating, sleep, exercise, and the use of fermented and distilled liquors. It is from the increase of excitability in old people, that so small a quantity of strong drink intoxicates them; and it is from an ignorance of this change in their constitutions, that many of them become drunkards, after passing the early and middle stages of life with sober characters.
Life is continued in a less imperfect state in old age in women than in men. The former sew, and knit, and spin, after they lose the use of their ears and eyes; whereas the latter, after losing the use of those senses, frequently pass the evening of their lives in a torpid state in a chimney corner. It is from the influence of moderate and gently stimulating employments, upon the female constitution, that more women live to be old than men, and that they rarely survive their usefulness in domestic life.
Hitherto the principles I am endeavouring to establish have been applied to explain the cause of life in its more common forms. Let us next inquire, how far they will enable us to explain its continuance in certain morbid states of the body, in which there is a diminution of some, and an apparent abstraction of all the stimuli, which have been supposed to produce animal life.
I. We observe some people to be blind, or deaf and dumb from their birth. The same defects of sight, hearing, and speech, are sometimes brought on by diseases. Here animal life is deprived of all those numerous stimuli, which arise from light, colours, sounds, and speech. But the absence of these stimuli is supplied,
1. By increased sensibility and excitability in their remaining senses. The ears, the nose, and the fingers, afford a surface for impressions in blind people, which frequently overbalances the loss of their eye-sight. There are two blind young men, brothers, in this city, of the name of Dutton, who can tell when they approach a post in walking across a street, by a peculiar sound which the ground under their feet emits in the neighbourhood of the post. Their sense of hearing is still more exquisite to sounds of another kind. They can tell the names of a number of tame pigeons, with which they amuse themselves in a little garden, by only hearing them fly over their heads. The celebrated blind philosopher, Dr. Moyse, can distinguish a black dress on his friends, by its smell; and we read of many instances of blind persons who have been able to perceive colours by rubbing their fingers upon them. One of these persons, mentioned by Mr. Boyle, has left upon record an account of the specific quality of each colour as it affected his sense of touch. He says black imparted the most, and blue the least perceptible sense of asperity to his fingers.
2. By an increase of vigour in the exercises of the mental faculties. The poems of Homer, Milton, and Blacklock, and the attainments of Sanderson in mathematical knowledge, all discover how much the energy of the mind is increased by the absence of impressions upon the organs of vision.
II. We sometimes behold life in idiots, in whom there is not only an absence of the stimuli of the understanding and passions, but frequently, from the weakness of their bodies, a deficiency of the loco-motive powers. Here an inordinate appetite for food, or venereal pleasures, or a constant habit of laughing, or talking, or playing with their hands and feet, supply the place of the stimulating operations of the mind, and of general bodily exercise. Of the inordinate force of the venereal appetite in idiots we have many proofs. The cretins are much addicted to venery; and Dr. Michaelis tells us that the idiot whom he saw at the Passaic falls in New-Jersey, who had passed six and twenty years in a cradle, acknowledged that he had venereal desires, and wished to be married, for, the doctor adds, he had a sense of religion upon his fragment of mind, and of course did not wish to gratify that appetite in an unlawful manner.
III. How is animal life supported in persons who pass many days, and even weeks without food, and in some instances without drinks? Long fasting is usually the effect of disease, of necessity, or of a principle of religion. When it arises from the first cause, the actions of life are kept up by the stimulus of disease[95]. The absence of food when accidental, or submitted to as a means of producing moral happiness, is supplied,