The blood, the fountain whence the spirits flow,
The generous stream that waters every part,
And motion, vigour, and warm life conveys
To every particle that moves or lives,
——————through unnumber’d tube.
Pour’d by the heart, and to the heart again
Refunded.—————
Armstrong.
Who in the dark the vital flame illum’d,
And from th’ impulsive engine caused to flow
Th’ ejaculated streams through many a pipe
Arterial with meand’ring lapse, then bring
Refluent their purple tribute to their fount:
Who spun the sinews’ branchy thread, and twin’d
The azure veins in spiral knots, to waft
Life’s tepid waves all o’er; or, who with bones
Compacted, and with nerves the fabric strung:
Their specious form, their fitness, which results
From figure and arrangement, all declare
Th’ Artificer Divine!
Bally.
Again:—
———The nerves, with equal wisdom made.
Arising from the tender brain, pervade
And secret pass in pairs the channel’d bone.
And thence advance through paths and roads unknown.
Form’d of the finest complicated thread,
The num’rous cords are through the body spread.
These subtle channels, such is every nerve,
For vital functions, sense, and motion serve;—
They help to labour and concoct the food,
Refine the chyle, and animate the blood.
Blackmore.
We now proceed to some Curious and Interesting Facts concerning Respiration, or the Act of Breathing.
Anatomists have, not unaptly, compared the lungs to a sponge; containing, like it, a great number of small cavities, and being also capable of considerable compression and expansion. The air cells of the lungs open into the windpipe, by which they communicate with the external atmosphere: the whole internal structure of the lungs is lined by a transparent membrane, estimated by Haller at only the thousandth part of an inch in thickness; but whose surface, from its various convolutions, measures fifteen square feet, which is equal to the external surface of the body. On this extensive and thin membrane innumerable branches of veins and arteries are distributed, some of them finer than hairs; and through these vessels all the blood in the system is successively propelled, by an extremely curious and beautiful mechanism, which will be described in some future article.
The capacity of the lungs varies considerably in different individuals.[3] On a general average, they may be said to contain about 280 cubic inches, or nearly five quarts of air. By each inspiration about forty cubic inches of air are received into the lungs, and at each expiration the same quantity is discharged. If, therefore, we calculate that twenty respirations take place in a minute, and forty cubic inches to be the amount of each inspiration, it follows, that in one minute, we inhale 800 cubic inches; in an hour, the quantity of air inspired will be 48,000 cubic inches; and in the twenty-four hours, it will amount to 1,152,000 cubic inches. This quantity of air will almost fill 78 wine hogsheads, and would weigh nearly 53 pounds. From this admirable provision of nature, by which the blood is made to pass in review, as it were, of this immense quantity of air, and over so extensive a surface, it seems obvious, that these two fluids are destined to exert some very important influence on each other; and it has been proved, by a very decisive experiment of Dr. Priestley’s, that the extremely thin membrane, which is alone interposed, does not prevent the exercise of the chemical affinity which prevails between the air which is received in the lungs, and the blood which is incessantly circulating through them. It must surely, therefore, be of the first importance to health, that the fluid of which we hourly inhale, at least, three hogsheads, should not be contaminated by the suspension of noxious effluvia.
The purity of the atmosphere may be impaired either by the operation of what some denominate natural causes, or by the influence of circumstances resulting from our social condition. Its chemical constitution is changed by respiration; the vital principle is destroyed, and its place supplied by a highly poisonous gas.
The emanations from the surface of our bodies contribute, in a still greater degree, to vitiate the atmosphere, and to render it less fit for the healthful support of life. Many of the organs which compose our wonderfully complicated frame are engaged in discharging the constituent parts of our bodies, which, by the exercise of the various animal functions, are become useless, and, if retained, would become noxious. Physiologists have instituted a variety of experiments, to ascertain the amount of the exhalations from the surface of the body. Sanctorius, an eminent Italian physician, from a series of experiments performed during a period of thirty years, estimates it as greater than the aggregate of all our other discharges. From his calculations it would appear, that if we take of liquid and solid food eight pounds in the twenty-four hours, that five pounds are discharged by perspiration alone, within that period; and of this, the greater part is what has been denominated insensible perspiration, from its not being cognizable to the senses. We may estimate the discharge from the surface of the body, by sensible and insensible perspiration, as from half an ounce to four ounces per hour.
The exhalations from the lungs and the skin are, to a certain extent, offensive even in the most healthy individuals; but when proceeding from those labouring under disease, they are in a state very little removed from putrefaction.