This section is from the book "Health", by W. H. Coefield.
The liver is the largest gland in the body. It is an organ situated on the right hand side of the abdomen, immediately underneath the diaphragm, to which it is attached by a strong fibrous ligament. It runs from the back right to the front of the abdomen close underneath the diaphragm, and its front edge overlaps the stomach.
I have already told you that a large portion of the blood of the body, namely, the blood which fcomes back from the walls of the stomach, the intestines, the spleen, and pancreas or sweetbread, and from a great part of the serous bag in which the intestines are enveloped, instead of going direct into one of the venae cavae, is conveyed into one large vein, which goes into the liver.
Now, besides that vein, an artery goes to the liver from the aorta or great artery which supplies the body. These two, the artery and the vein, go into the liver at the same place.
I have just said that the liver is a gland, and I have before said that when I speak of a gland I mean a true gland, and I mean by a true gland an organ that is formed around a projection from the skin or the mucous membrane of the body, or, if you like, that has a tube from it leading to the surface of the skin or of the mucous membrane; that tube we call the duct of the gland.
The liver I call a gland, then, and it has a duct or tube leading to the surface of the mucous membrane, viz., the mucous membrane of the small intestines near their beginning. That duct is called the bile-duct It comes from the liver, and it comes from the same place where the vein and artery enter the liver; so that we have three vessels, the vein and the artery going into, and this bile-duct coming out of, the liver at the same place.
If we follow them we find that they run through the substance of the liver together, and that their branches run alongside of one another, and are enclosed in the same fibrous capsule.
We find, further, that the portal vein and the artery send out still smaller branches into the very intimate structure of the liver, and that they each end in capillary vessels, and in the same set of capillary vessels, between the little pieces of which the liver is composed, called by anatomists the lobules of the liver.
These capillary vessels then ran into the lobules and are collected into small veins, which start from the middle of those lobules of which the liver is composed, and run on joining one another and forming larger veins, at last to join together in one large vein, leaving the liver in another place and entering the vena cava inferior, which runs close behind the liver through the diaphragm to the right auricle of the heart.
The bile-duct is contained in the same capsule as the portal vein and the liver artery, and begins by small branches in between the lobules of which the liver is composed; these small branches run together and form the proper duct of the liver-the bile-duct.
What goes into the liver ? In the first place, the arterial blood goes to the liver by the liver artery, just as it does to every other organ of the body; then, in the next place, venous blood goes into it by the portal vein. That venous blood is blood that comes chiefly from the walls of the stomach and small intestines.
You remember I told you that in the small intestines a very large proportion of the soluble matter of the food is absorbed by the capillary vessels in the villi of the mucous membrane.
So you see that the liver is in the first place supplied with arterial blood, and in the second place with blood containing a large proportion of the nutritious parts of the food. What does it do with that blood ? The most obvious answer is, that it secretes bile from it; but it does something else of far greater importance.
It is found that whether there is any sugar or not in the blood which goes to the liver, this organ has in some way or another the property of preparing from the blood a kind of starch, which goes by the name of liver starch, and by half-a-dozen other names, and the liver prepares at the same time another substance, which is called a ferment, and which is capable of changing that starch soon after it is made into fat, so that the liver is a kind of manufactory of fat; it is able to manufacture a kind of substance resembling starch out of the blood, and to store it up for future use, and it is capable also of turning that same substance into fat. That is the first and most important property of the liver. That leads us to see why it is that the blood that has been absorbed, containing some of the most nutritious .parts of the food, should go straight to the liver and not first to the tissues of the body to nourish them.
The. liver, besides this, secretes bile. It separates from the blood a liquid having very important properties, which is partly a waste liquid, and partly useful. Bile has the property of helping the pancreatic juice to subdivide the fats, so that they are capable of being absorbed into the lacteal vessels, and it contains important resinous matters which stimulate the. action of the intestinal canal, so that whenever anything occurs to prevent the proper secretion of bile by the liver the action of the intestinal canal becomes at once very sluggish; it does not get the stimulus that the resinous matters in the bile provide; the bile acts also as a very important antiseptic, and when its secretion is in any way impeded, the food is very liable to decomposition in the intestines. So you see that the liver is a very important organ.
A great part of the bile is absorbed into the blood, so that as it is absorbed into the blood of the intestines, and comes back through the portal vein to the liver, it would seem as if certain parts of the bile travelled in a circle to and from the liver. Only a small portion of the bile, more especially the colouring matter, is excreted as waste matter.
The liver is also said by some physiologists to be one of the sources of the white corpuscles of the blood. It is known that in the blood that leaves the liver a larger proportion than usual of white corpuscles exist. It is believed to be an organ in which waste red corpuscles are got rid of (because they waste, just as all the other parts of the body do), and some parts of the bile consist of substances of which these red corpuscles were composed.