in the animal economy is more curious and wonderful, than the action of that class of organs of which the pylorus affords a remarkable example. If a portion of undigested food presents itself at this door of the stomach, it is not only not permitted to pass, but the door is closed against it with additional firmness; or, in other words, the muscular fibres of the pylorus, instead of relaxing, contract with more than ordinary force. In certain cases, or where the digestion is morbidly slow, or when very indigestible food has been taken, the mass is carried to the pylorus before it has been duly acted on by the gastric juice; then, instead of inducing the pylorus to relax, in order to allow of its transmission to the duodenum, it causes it to contract with so much violence as to produce pain, while the food thus retained in the stomach longer than natural, disorders the organ; and if the digestion cannot ultimately be performed, that disorder goes on increasing until vomiting is excited, by which means the load that oppressed it is expelled. The pylorus is a guardian placed between the first and the second stomach, in order to prevent any substance from passing from the former until it is in a condition to be acted on by the latter; and so faithfully does this guardian. perform its office, that it will often, as we have seen, force the stomach to reject the offending matter by vomiting, rather than allow it to pass in an unfit state; whereas when chyme, duly prepared, presents itself, it readily opens a passage for it into the duodenum."* How serious would have been the mischief resulting to the whole frame, if some such expedient had not prevented the too early transference of the contents of the stomach to its next stage? On this our health and strength in a great measure depend. And can it be believed that so necessary and beneficial an arrangement is the result of accident and undesigning * Library of Useful Knowledge.-ANIMAL PHYSIOLOGY, p. 41.

necessity? Is not the wisdom that built the human frame apparent here?

But the process goes on; and as the substance now called chyme moves forward, it receives other changes from peculiar fluids, secreted just in the proper place and applied just at the proper time, the principal of which appears to be the bile, prepared by the liver, and exuded by a duct so as to mix with the chyme in the duodenum. Another change is the consequence of this; its purest portions then separate into chyle, a cream-like liquor, which passing slowly along the intestines, gradually disappears, being absorbed by the lacteals, an innumerable quantity of hair-like vessels, which uniting, pass by a circuitous route into the thoracic duct, the contents of which are poured into a large vein communicating with the heart. The chyle thus mixes with the blood, and is then prepared for circulating through the system. How truly admirable are those processes, how wonderful and complicated the apparatus, how exact all the arrangements by which the food we eat, whether vegetable or animal, seeds or fruits, is converted into that vital fluid which ministers nutrition to the whole system, and supplies its constant waste. What chemical laboratory, with its furnaces, and crucibles, and alembics, all in full action, can give stronger proofs of intelligence and design?

But we must notice in the next place, though with a far greater attention to brevity than the subject deserves, the manner in which the preparation thus formed is distributed through the system. The whole circulation of the blood depends on the heart. Centrally situated in those domains, every part of which it is to supply with aliment, and that without intermission, it is well secured as within the walls of a citadel, and is furnished with a case which protects it, keeps it lubricated, and affords room for its constant play. The heart is a strong muscle, of a very peculiar kind,

constructed with the most obvious design of performing the important function assigned to it. It is a kind of double organ, consisting of two parts and sets of apparatus, which perform distinct offices. These two parts, however, are not like the pairs of organs and limbs which we possess, such as two eyes, two ears, and two hands, each one of which is completely independent of the other, and capable of performing separately the full office of that organ or limb. But, though it appears possible that the right and left portions of this organ might have acted separately, yet both are absolutely necessary, and their union probably gives strength to the structure and power to its movement. Each portion of the heart is furnished with two cavities, an auricle and ventricle; and each portion has a large artery and vein communicating with it. Each part also superintends a circulation of its own. To the right, is assigned the circulation of the whole mass of blood through the lungs; and to the left, its distribution through all the other parts of the body. The venous blood, which, after circulating through the system, becomes of a dark purplish colour, and is incapable of supporting life, enters the right portion of the heart by the vena cava, and is sent through the lungs by the pulmonic artery; the purified stream passes into the left portion of the heart by the pulmonic veins, and is propelled through the aorta, and thence by the smaller arteries through the whole system. The proofs of a surpassing wisdom, in the construction and functions of the heart, are many and striking; we can only glance at a few.

How can it be imagined that the peculiar irritability of the heart, and its alternate contraction and dilatation can be an accidental thing? Without these functions, life could not be carried on; and these peculiarities no other muscle possesses. As the blood enters, the right auricle of the heart expands, by its peculiar sensibility to the presence of this

fluid it contracts, and propels it into the right ventricle; as the auricle contracts the ventricle enlarges, and excited in its turn by a sudden stroke, it sends its contents through the pulmonic artery into the lungs. On the left side a similar process goes on with the blood received from the lungs and driven through the aorta. Who can bring himself to believe that, by any accidental concurrence of various particles of matter, by any "affinities" or "analogies," such an organ should be, formed, with parts so distinct yet united, and endowed with a power of alternately contracting and expanding, so remarkable yet so necessary, performing its motions with such a regularity and constancy, for so many years, day and night, by its own power of action, altogether independent of our will? Why should it have auricles and ventricles, each moving in its own due time,-why should the arteries and veins be so placed as to keep the venous and arterial blood in separate chambers? Why should this muscle only have just such power, and why should its action, a very short suspension of which would be fatal, be rendered, differently from the greater part of the muscles, independent of the will? How can we, without shutting our eyes, fail to perceive those distinct marks of benevolent design which all this exhibits?

And how wisely is the venous blood prevented from mixture with the arterial, when both are in the same organ and that at the same time! The most injurious consequences would ensue, if they were not kept distinct. The cavities which are the receptacles of this fluid, in its two different conditions, are separated by a fleshy wall, which allows of no communication.* No two liquids, the mixture of which

* A case is mentioned by Richerand, of very singular conformation of the heart, in which the blood was allowed to pass from the left to the right ventricle, as it was found on dissection. By another peculiarity, the impure blood was not transmitted to the brain, so as to disturb its vital excitement; but the patient, when brought to the hospital, "was remarkable for the lividity of his complexion, the

is undesirable, are ever kept separate with more evident design and care.

What is a more evident proof of contrivance and design, than when vapour or fluid is intended to pass in one direction only, a valve is so placed as to permit its course freely in this direction, and to close and effectually prevent its return? You are familiar with such constructions, you know by daily experience that the utility of such an invention is quite equal to its ingenuity; you are aware that the whole working of many an important piece of machinery depends on a valve. And was there not one also who knew that all the machinery of life depended on the position and efficient working of a valve? In almost all the vessels which convey a liquid to any part of the human frame this expedient may be found; in the veins, the lacteals, and lymphatics; but there are none, the office of which is more important, and in which the precaution of intelligence is more impressively exhibited, than in the valves of the heart. When the dark venous blood has reached the right ventricle of the heart, and this by a sudden contraction empties itself into the pulmonic artery, to send it to the lungs, what is to prevent its expelling a large portion of it into the auricle from which it received it? Here a valve is placed, called from its shape the tricuspid valve, fastened most curiously and strongly, by fine tendons, to the sides of the heart. No sooner is the blood forced from the ventricle than it drives back the valve and closes this passage, and the only way by which this vital stream can go, is the right way; it then proceeds without obstruction through the artery to the lungs. But here occurs another difficulty to be provided for; as soon as the turgescence of the vessels of the conjunctiva, and the thickness of his lips, which, like the rest of his face, were of a dark colour, his respiration was laborious, his pulse irregular, he could not utter two words in succession, without taking breath; and was obliged to sleep in a sitting posture."-Richerand's Physiology, pp. 151, 152, ed. 3d.