the minute branches of the pulmonary artery, thus exposed for the aëration of the blood through the lining membrane of the air-cells. In this manner, around each branch there are myriads of lung-cells arranged; and as we inspire, we bring as much air as they can hold into contact with the pulmonary capillaries, the coats of which are pervious to air, and which thus purify the blood in the act of inspiration. The space covered by the capillary tubes of the entire lung-structure, all busy in this work of purification, would be immense, if spread out on a level surface. It has been estimated that these lung-cells would, if fully extended, cover a space equal to twenty times the surface of an average-sized human skin. On so large a scale, then, is this system of blood-purification conducted. To what an immense extent is air thus acted on by these capillaries, and what an amount of work must they do in the course of a life of three-score years and ten! In the minute as well as in the vast we see the wondrous footprints of Almighty power. What an exact mechanism there must be in our lungs, which are the workshop of such constant activities, where action and reaction, the removal of effete matter, and the restoration of the purity of the blood, are so perfect and so undisturbing that we breathe tranquilly on amidst it all, unconscious of what is doing within!

The lungs are constantly blowing out of the body carbonic acid, formed from animal material, and used up in the great human laboratory. They part with what would be a deadly poison if retained. It has been estimated that every man secretes from his lungs and skin daily, at the very lowest amount, ten ounces of solid carbon, which makes, after combining with oxygen, thirty-seven thousand cubic inches, or twenty-one cubic feet of gas. Now, our best authorities say that we cannot live in an atmosphere containing more than five or six per cent. of carbonic acid. Here, then, we have in respiration, as in other functions, the escape, by natural healthy laws, of a morbific product from our own system. How necessary it is, that this as well as all other corporeal exhalations should be dissipated by currents of air in crowded rooms, or among crowded populations! Hence, the necessity to sound health of good fresh air, night and day. Provided the air does not blow directly on us, it is well, even in a bed-room, to have a current of air in some part of the room. Fortunately, in all our rooms fresh air is constantly entering, by apertures connected with doors, windows, and fire-places. In an air-tight room of ordinary size, any man shut up for a few hours would die of suffocation as certainly as if he had been strangled; for the air would soon be found to contain more than five parts in a hundred of carbonic acid.

In that peculiar state bordering on death, called "trance," when neither pulse nor respiration is perceptible, the human body exhales so little carbon that it can be shut up in a coffin for some time without extinguishing the remaining flickering taper of life; but, if the dying flame should again blaze out, the man must soon die, unless (the vital function returning slowly, and with imperfect carbonic exhalation) some act of the attendants,

or the jolting of his coffin, should awake him in time to make the very little noise, which, coming from the apparently dead, will send, it is true, some scampering away, from their dread of the supernatural; but which is equally sure to bring more loving friends, to welcome him back to his home and family.

One of the best-authenticated instances of trance is that of the daughter of Henry Laurens, the President of the first Congress General of the United States of America. When an infant, she had the small pox, and was laid out as dead. The window of the apartment, which had been carefully closed during the progress of the disease, was thrown open to ventilate the chamber; when the fresh air revived the supposed corpse, and restored her to her family.

The bearing of animal heat on the waste and supply of the system is very simple. Heat is evolved in very many chemical combinations. Combustion is only the act of combination, of carbon and other elements, with oxygen chiefly. In the waste and supply of the human system we have oxygen, hydrogen, nitrogen, carbon, sulphur, phosphorus, at work, along with many other substances which combine for the most part with oxygen and hydrogen. Here we have the source of all the complex processes of animal chemistry. In these heat is evolved,—heat which, in the healthy condition of the body, is coeval with the first dawning of life, and ends only when the icy hand of death is placed on its frail organism. This heat, in a healthy body, is always kept at a fixed standard, partly by animal processes, and partly by a proper arrangement of external influences; kept at about 98° Fahrenheit, in all seasons, climates, and exposures. As soon as we are getting below 98°, we suffer from cold; and we adopt means to prevent the further escape of heat, or we resort to artificial warmth. As soon as we are hotter than 98°, our discomfort leads us to adopt means of cooling ourselves: if we fail, we soon incur some form of disease, and die. If we are wrapped up in unnecessary clothing, we suffer because we do not part with the superfluous heat, formed in the body by the chemical changes necessary for health.

We have not yet had solved for us some questions connected with the formation of animal heat. But, whatever may be its causative elements, we cannot but see that so strange a phenomenon as that of its continual development in the living frame is one of the clearest marks of a designing Mind in the material world. Even the maintenance of the precise degree of heat is a very interesting phenomenon,-just so much, 98° Fahrenheit, and no more. More would destroy this wondrous fabric of ours; less will not answer for the functions to be performed. One of the chief means by which the warmth of the body retains its natural standard of 98°, even in the open air at the noon-tide of the tropical sun, is the evaporation, and consequent loss of heat produced by perspiration. This is both a result and at the same time a remedy for the over-heating of the body. Nature thus puts an evaporating lotion over its surface as soon as we begin to suffer from undue increase of temperature. The reason of the sensation of 4 c

VOL. XI.-FIFTH SERIES.

coldness, produced by perspiration, will scarcely be understood but by those who have studied the phenomena of latent heat. During the conversion of a fluid into vapour, heat becomes latent, and therefore not felt; hence the sensation of coldness, according to the older chemists. The modern chemist gives the simple statement of the fact that heat is thus changed into mechanical repulsive force. Either principle explains the loss of heat. And the latter principle is looked upon as involving facts which constitute part of the proof of the identity or correlation of heat, electricity, and of all the other mechanical powers.

It is interesting to notice how warmth is preserved in winter by the mantle of snow or ice thrown over the earth; both of which, being non-conductors, retain the heat in the ground, and rivers, and lakes, and prevent the vegetable and animal life beneath from being destroyed. Snow and ice are thus messengers of God, to keep up the amount of warmth requisite for animal and vegetable life. During winters in North America, where the atmosphere is at several degrees below zero Fahrenheit, the water beneath the ice will seldom fall below 35°; the ice above being a non-conductor of the heat of the earth below the water. Fish thus live there fully supplied with animal heat; and in condition to enjoy the functions of healthy life, or to minister to the wants of man. We cannot dismiss this topic without stating, as bearing on it, one of the most important principles in the practice of medicine. There is an intimate relation between animal heat and the use of oleaginous or fatty matters. In cold weather, we have, if we are in good health, a hankering after fatty kinds of food; and we can then easily digest them. And the colder the climate, the more prevalent is this sort of appetite, until we come to the frozen regions, where the Laplander drinks train-oil, and eats blubber, rather than be without fat. Hence, Christmas has always been the time for living on the "fat of the land." Homer represents his heroes as eaters of fat food. There is also another article of food that we eat chiefly in winter. Nuts are vegetable oils, used not only by man, but by some of the lower animals, as squirrels, for example, which lay them up chiefly for winter. Although more especially needed in cold weather, these fatty forms of nutriment are required more or less in all climates. Thus, in tropical regions, palm oil is a requisite among the hardy children of the sun. The cocoa-nut, chiefly a carbonaceous fruit, and therefore heatproducing, is another part of the food of hot countries. In the oldest of parables, the olive is represented as saying, "Should I leave my fatness, wherewith by me they honour God and man?"

We can only conclude this subject by observing that these arrangements in our physical frame distinctly point to method, to motives, and to design, all of which imply a presiding Power, which, the more we consider the results, must be recognised as infinite. Every philosophical investigation of nature (more and more) clearly reveals the perfections of her Author. In the view of the physiological changes in which we are concerned, we ought surely to feel, as well as tamely to admit, that we "are fearfully and wonderfully made." It was to assert the being and wisdom of God, that one

of Job's friends pointed to His works in external nature, the wild goat on the rock, the ass of the desert, the strength of the rhinoceros, the goodly wings of the peacock, the feathers of the ostrich, and the instinct with which she leaveth her eggs in the earth, and warmeth them in the dust; the power and pride of the horse, the flight of the hawk, the strength and cunning of the eagle. And it is the "Inspiration" only of the same intelligent Power,-the eternal Wisdom,-that "giveth us understanding."

SELECT LITERARY NOTICES.

[The insertion of any article in this list is not to be considered as pledging us to the approbation of its contents, unless it be accompanied by some express notice of our favourable opinion. Nor is the omission of any such notice to be regarded as indicating a contrary opinion; as our limits, and other reasons, impose on us the necessity of selection and brevity.]