It buds off from the food tube just below the stomach, so that its waste tube, the _bile duct_--about the size of a goose quill--opens into the upper part of the intestine.
The main work of the liver is to receive the blood from all over the body and to act upon its waste substances, burning them up so that they can be taken up, and got rid of, by the glands of the skin and the kidneys.

In the process it very frequently changes these waste substances from poisonous into harmless forms; and even when disease germs get into the body and infect it, the poisons, or toxins, which they pour into the blood are carried to the liver and there usually burned up, or turned into harmless substances.
The liver is, therefore, to be regarded as a great _poison filter_ for the entire body.

So long as it can deal with the poisons as fast as they are formed, either by the body itself, or in the food, or by disease germs, the body is safe and will remain healthy.

But if the poisons come faster than the liver can deal with them, as, for instance, when we have eaten tainted meat or spoiled fruit, or have drunk alcohol, they begin to poison our nerves and muscles, and we become, as we say, "bilious." Our head aches, our tongue becomes coated, we have a bad taste in the mouth, we lose our appetite and feel stupid, dull, and feverish.
Such waste materials as the liver cannot burn down so that the kidneys and skin can handle them, it pours out through its duct into the intestine as the bile.

The bile is a yellowish-brown fluid, which assists the pancreatic juice in the digestion of the food, and helps to dissolve the fats eaten, but is chiefly a waste product.