blood, but a fluid which is secreted and formed from it, for a special purpose.

When one layer, so to call it, of the mass in the stomach, is formed into chyme, it is carried out of the stomach, or,

Here are seen, first, the oesophagus, next the stomach, and last the small intestines, constituting the whole alimentary canal, which is nearly thirty feet in length. The gall bladder may be scen on the left.

rather, beyond it, into the small intestines. This is performed by a kind of churning motion, which will be described hereafter. Another layer of chyme is thus formed and disposed of; then another; and so on, till the work is finished. This work of chymification, as a general rule, takes up from three to four hours; but circumstances so greatly vary it, that the exceptions may seem to exceed the general rule. Few persons so far conform to the laws of digestion as to render this process at all natural, or healthful.

The small intestines, which receive the chyme from the stomach, are some twenty-five feet or more in length, and very crooked. Over the internal surface of this long, winding canal, especially the first portion of it, the chyme is spread out, where it soon undergoes another change, not less important than the first.

This change consists essentially in the addition to the chyme of two fluids, viz., the bile and the pancreatic juice; and the formation, by what is called secretion, of a new substance, called chyle.

In this engraving, the stomach is removed to show the pancreas behind it. What you see on the right is the spleen, whose use is not well known. Above is the liver, turned up, so as to exhibit the gall bladder and the duct through which the bile flows into the intestines.

The chyle is usually of a milky or pearl-colored appearIt is first seen in small vessels called lacteals, (milk

ance.

vessels,) whose mouths open, in great numbers, on the inner coat of the intestines.

These lacteals, beginning thus, by their open mouths, in the lining membrane of the intestines, pass through what is called the mesentery to a large reservoir or repository, at

This is to exhibit the lacteals, the mesentery, the receptacle of the chyle, and the duct which carries the chyle to the vein at the left shoulder.

the back part of the abdomen, denominated the receptacle of the chyle. From this reservoir the chyle is carried, by a duct of considerable size, along upward, close to the spine, to a large vein near the left shoulder, into which it discharges its contents, which are thence carried, mingled with the dark, venous blood, to the right side of the heart, and afterwards to the lungs.

What remains of the food, such as the skins or rinds of vegetables, the seeds of fruits and other substances, which are insoluble, together with (in certain diseased conditions of the system) unchanged portions of the food, is carried along the canal, to be in due time ejected from the body. The time required for this may be greater or less, according to circumstances.

Something depends, in this particular, on the frequency or infrequency of our meals. They who eat but two or three times a day, and eat regularly, require more time than they who eat oftener. They who eat five or six times a day, or are irregular with regard to their times of eating, have, in the same proportion, more frequent peristaltic move

ments.

The chyle, though mingled with the venous blood and carried to the heart, appears still to be chyle. It has, indeed, many of the properties of a living fluid, like blood; but it is as yet imperfect-unfit to support life; nor is it nutritive till it has been carried from the heart to the lungs, when and where it receives its red color. But what the coloring matter of the blood is has been, and still is, a subject of much speculation, and not a little experiment. In practice, however, like many other nice points of physiology, these are matters of no great importance. We know that it is chyle when it is first mingled with the blood; we know that it is

blood after it has passed through the lungs. Perhaps this is enough.

Thus we have seen that the work of digestion consists of three or four separate processes. First, the preparatory process, in the mouth; secondly, the formation of chyme, in the stomach; thirdly, the change of chyme into chyle; finally, the change of chyle into blood. The last-mentioned process, however, is not usually considered as belonging to the work of digestion.

This description, though brief, sufficiently points out the offices of the organs concerned. The laws of digestion as we shall see in passing — are, for the most part, based on structure, and derived from it; and are all in harmony with it. My constant appeal, in support of the doctrines I shall advance, both in this lecture and every other, will be "to the law and to the testimony."

II. PARTICULAR LAWS IN RELATION TO DIGESTION.

LAW 1. Our Food must be well masticated, and commingled with Saliva.

Some have supposed that, if our food were properly reduced to pulp before entering the stomach, it made little difference how; but this is a great mistake. And yet, if the notion were true, teeth and salivary glands would still be quite convenient. Not every individual is so fortunate, in the journey of life, as to have always at hand warm water or any other solvent, or a pestle and mortar.

Much information on this subject has been obtained by the experiments of Dr. Beaumont, of Plattsburg. He had under his care, for many years, a young man with an un