II. DIGESTION.

Such a body would require for daily food, carbon 4,coo grains, nitrogen 300 grains; which, with the other necessary elements, would be most conveniently disposed in

which, in turn, might be obtained, for instance, by means

The fæces passed, per diem, would amount to about 2,800 grains, containing solid matter 800 grains.

III. CIRCULATION.

In such a body the heart would beat 75 times a minute, and probably drive out, at each stroke from each ventricle, from 5 to 6 cubic inches, or about 1,500 grains of blood.

The blood would probably move in the great arteries at a rate of about 12 inches in a second, in the capillaries at I to 1 inches in a minute; and the time taken up in performing the entire circuit would probably be about 30 seconds.

The left ventricle would probably exert a pressure on the aorta equal to the pressure on the square inch of a column of blood about 9 feet in height; or of a column of

mercury about 9 inches in height; and would do in 24 hours an amount of work equivalent to about 90 foot-tons; the work of the whole heart being about 120 foot-tons.

IV. RESPIRATION.

Such a body would breathe 15 times a minute.

The lungs would contain of residual air about 100 cubic inches, of supplemental or reserve air about 100 cubic inches, of tidal air 20 to 30 cubic inches, and of complemental air 100 cubic inches.

The vital capacity of the chest—that is, the greatest quantity of air which could be inspired or expired—would be about 230 cubic inches.

There would pass through the lungs, per diem, about 350 cubic feet of air.

In passing through the lungs, the air would lose from 4 to 6 per cent. of its volume of oxygen, and gain 4 to 5 per cent. of carbonic acid.

During 24 hours there would be consumed about 10,000 grains oxygen; and produced about 12,000 grains carbonic acid, corresponding to 3,300 grains carbon. During the same time about 5,000 grains or 9 oz. of water would be exhaled by the lungs.

In 24 hours such a body would vitiate 1750 cubic feet of pure air to the extent of 1 per cent., or 17,500 cubic feet of pure air to the extent of 1 per 1,000. Taking the amount of carbonic acid in the atmosphere at 3 parts, and in expired air at 470 parts in 10,000, such a body would require a supply per diem of more than 23,000 cubic feet of ordinary air, in order that the surrounding atmosphere might not contain more than 1 per 1,000 of carbonic acid (when air is vitiated from animal sources with carbonic acid to more than 1 per 1,000, the concomitant impurities become appreciable to the nose). A man of the weight mentioned (II stone) ought, therefore, to have at least 800 cubic feet of well-ventilated space.

V. CUTANEOUS EXCRETION.

Such a body would throw off by the skin of water about 18 ounces, or 10,000 grains; of solid matters about 300 grains; of carbonic acid about 400 grains, in 24 hours.

VI. RENAL EXCRETION.

Such a body would pass by the kidneys-of water about 50 ounces; of urea about 500 grains; of other solid matters about 500 grains, in 24 hours.

VII. NERVOUS ACTION.

In the frog a nervous impulse travels at the rate of about 80 feet in a second.

In a man a nervous (sensory) impulse has been variously calculated to travel at 100, 200, or 300 feet in a second.

VIII. HISTOLOGY.

Red corpuscles of the blood are about in breadth; white corpuscles th. Striated muscular fibres are about

breadth; plain both.

250

th of an inch

th of an inch in

Nerve-fibres vary betweenooth and 20th of an inch in breadth.

Connective tissue fibrils are about th of an inch in breadth.

Epithelium scales (of the skin) are about th of an inch in breadth.

Capillary blood-vessels are from both to zoooth of an inch in breadth.

Cilia (from the wind-pipe) are about gooth of an inch in length.

The cones in the "yellow spot” of the retina are about 10000th of an inch in breadth.

APPENDIX B.

THE CASE OF MRS. A— (See p. 240.)

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(1) THE first illusion to which Mrs. A. was subject, was one which affected only the ear. On the 21st of December, 1830, about half-past four in the afternoon, she was standing near the fire in the hall, and on the point of going up to dress, when she heard, as she supposed, her husband's voice calling her by name : come here! come to me!" She imagined that he was calling at the door to have it opened; but upon going there and opening the door, she was surprised to find no person there. Upon returning to the fire she again heard the same voice calling out very distinctly and loudly, " come, come here!" She then opened two other doors of the same room, and upon seeing no person, she returned to the fireplace. After a few moments she heard the same voice still calling, "Come to me, come ! come away!" in a loud, plaintive, and somewhat impatient tone; she answered as loudly," Where are you? I don't know where you are," still imagining that he was somewhere in search of her; but receiving no answer, she shortly went upstairs. On Mr. A.'s return to the house, about half an hour afterwards, she inquired why he had called her so often, and where he was, and she was of course greatly surprised to learn that he had not been near the house at the time. A similar illusion, which excited no particular notice at the time, occurred to Mrs. A. when residing at Florence, about ten years before, and when she was in perfect health. When she was undressing after a ball, she heard a voice call her repeatedly by name, and she was at that time unable to account for it.

(2) The next illusion which occurred to Mrs. A. was of a more alarming character. On the 30th of December, about four o'clock in the afternoon, Mrs. A. came downstairs into the drawing-room, which she had quitted only a few minutes before, and, on entering the room, she saw her husband, as she supposed, standing with his back to the fire. As he had gone out to take a walk about half an hour before, she was surprised to see him there, and asked him why he had returned so soon. The figure looked fixedly at her with a serious and thoughtful expression of countenance, but did not speak. Supposing that his mind was absorbed in thought, she sat down in an arm-chair near the fire, and within two feet, at most, of the figure, which she still saw standing before her. As its eyes, however, still continued to be fixed upon her, she said, after the lapse of a few minutes, "Why don't you speak?" The figure immediately moved off towards the window at the further end of the room, with its eyes still gazing on her, and it passed so very close to her in doing so, that she was struck with the circumstance of hearing no step or sound, nor feeling her clothes brushed against, nor even any agitation in the air.

Although she was now convinced that the figure was not her husband, yet she never for a moment supposed that it was anything supernatural, and was soon convinced that it was a spectral illusion. As soon as this conviction had established itself in her mind, she recollected the experiment which I had suggested of trying to double the object; but before she was able distinctly to do this, the figure had retreated to the window, where it disappeared. Mrs. A. immediately followed it, shook the curtains, and examined the window, the impression having been so distinct and forcible, that she was unwilling to believe that it was not a reality. Finding, however, that the figure had no natural means of escape, she was convinced that she had seen a spectral apparition like that recorded in Dr. Hibbert's work, and she consequently felt no alarm or agitation. The appearance was seen in bright daylight, and lasted four or five minutes. When the figure stood close to her, it concealed the real objects behind it, and the apparition was fully as vivid as the reality.

(3) On these two occasions Mrs. A. was alone, but when