danger to be apprehended, as many suppose, of taking cold by it.

Among thousands who have been influenced by hints like these, I never knew but one instance of injury. This was a little child near Hartford, Connecticut. The father, having read my tract on "Breathing Bad Air," undertook to profit from it, by raising his window at night, and sleeping with it open. The father was benefited; the mother was not injured; but the child caught cold, and suffered considerably.

One of the individuals who have profited most from sleeping with his window open during the night is a son of Fisher Ames, of Dedham, Massachusetts. He has thus slept for nearly twenty years, both in summer and winter; and I cannot learn that he ever caught cold in this way in his life.

But let me be fully understood; I do not recommend the practice, except as a choice of evils. It is safer- very much safer than no ventilation at all. It is, indeed, sometimes quite safe. It is better, however, in general, to have an opening near the bottom of the room, even if it is no larger than a common stove pipe; but the opening, if not into a chimney, should be central.

There will be far less of suffering for want of proper ventilation when we return to the good old custom of using fireplaces. Not such fireplaces as I have seen, large enough almost to hold half a cord of wood, but fireplaces of moderate dimensions.

One obvious advantage to be derived from the general use of fireplaces is this: When we can see the fire, we are far better satisfied with a lower temperature than when it is hid from our view. I think the majority of mankind would be as well satisfied with sixty degrees of Fahrenheit, when they

have a fire in sight, as with sixty-eight or seventy degrees in other circumstances.

Another advantage is, that they are healthier. For, say what we will, there are no fixtures for heating our rooms which are so conducive to health as the reasonable fireplace. Our rooms are not apt to become so hot under its use, and it ventilates better. We spend a little more for fuel, perhaps, but less for medicine, physicians, and grave diggers. Indeed, if an estimate could be made of the expense of all the stoves which have been made old fashioned and new fashioned during the last twenty-five years, and if this were added to the expense for fuel, I think the sum total would be greater than the expense of furnishing wood for fireplaces of reasonable dimensions for the same time.

Unpopular, therefore, as it may be, I do most earnestly and sincerely look forward to a period when there will be a return to the custom of depending chiefly on fireplaces for warming our rooms not only the rooms of our dwelling houses, but our school rooms, counting rooms, &c. Not but that, in some few instances, here and there the stove will continue to be used; as, perhaps, the cooking stove or cooking range in our kitchens. To use the article, however, will not be, as now, the general rule, but only the exception.

As for the air-tight stove, of which so much is made by many, I can hardly believe it will be found indispensably necessary. In our efforts to retain the heat, we retain also the bad air; and in a proportion exactly commensurate. Of all our stoves, therefore, they are the worst.

Our churches the main body of the buildings, I mean are of late tolerably well ventilated. More improvement has taken place in this direction than in any other. Still there are ministers who have the reputation of delivering sleepy

sermons, and many more hearers who are reputed to be sleepy, when the fault is as much with the air as with any thing else, except, perhaps, heavy dinners. And yet, notwithstanding the increasing attention to our churches, thousands of lecture rooms or vestries, to say nothing of other public buildings, are as much neglected as our school houses and sleeping rooms. Sextons are nearly as ignorant of the laws of ventilation as teachers; and some of them appear to be still more reckless. We do not uniformly select this kind of public servants from the more intelligent of society, but frequently from a very different class.

LECTURE IV.

CIRCULATION AND RENOVATION.

GENERAL REMARKS.

THE blood is a very important part of the human machinery; and its nature and offices, as well as the means of preserving it in health, can never be too fully understood. It is usually said to amount to twenty-five or thirty pints or pounds; and to constitute about a fifth of the whole weight. It varies, however, very greatly. Some adult individuals have little more than twenty pounds of blood in them; others have twenty-five; and others thirty, perhaps even more.

There are other fluids in the human system, most of which are secreted or made from the blood; but they can hardly be considered as forming component parts of it. Reckoning up every thing which can, by possibility, be resolved into a liquid. or semi-liquid, we have at least four fifths of the body liquid, and only one fifth of it solid. Some place the fluid parts at more than five sixths. The particular character of this wonderful fluid, made from our food in so wonderful a manner, and performing offices apparently little short of miraculous, will appear more fully in the progress of my remarks.

Let us, then, proceed to consider, 1. The mechanism of circulation ; 2. Its offices; 3. Its laws; and, 4. Its diseases. On all these points, however, I must be short.

I. MECHANISM OF THE CIRCULATION.

The human circulation is performed chiefly by the heart,

the arteries, the veins, and the capillaries. There are other agents, but these are the principal.

The heart, in man, is double, as if two hearts, placed in close contact, were made to adhere. It is about the size of the clinched or doubled fist. In many of the lower animals, such as fishes and reptiles, the heart is single.

lows.

The Heart.

Each division of the human heart has two cavities or holOne is called the auricle the other the ventricle. The auricle is much smaller than the ventricle. Both, however, are fleshy in their construction, and very strong.

The right auricle and right ventricle

venous blood; the left, arterial blood.

contain what is called

Except in a diseased

state of this important organ, there is no connection or com