The bile contains two classes of constituents, one of which are true secretions, and destined to re-enter the system and perform certain functions. They contain, with other 'natters, some that are formed in the liver, and are no doubt elaborated from materials furnished by the blood. These are the salts included in the above table under the names of tauroeholate and glycocholate of soda. Biliverdine, the coloring matter of the bile, is probably a mixture of different coloring principles which undergo rapid change .on exposure to the air. It has some analogy to the coloring matter of the blood, and it is also, like the biliary salts, supposed to be formed in the liver. This coloring matter has intense power, and in cases of obstruction of the biliary passages will give the skin and conjunctivEc a decidedly yellow color. Like hemoglobine, it contains a portion of iron, but the relative amount has never been ascertained. The other constituent of the bile is truly excretory, being composed of effete matter brought by the blood-vessels from the various parts of the system. This excretory constituent is cholesterine, a sub .stance which has long been known as a constituent of the bile, whose chemical and physical characteristics were well recognized, but whose physiological relations were not understood. It was reserved for Dr. Austin Flint, jr., of New York, to discover these and make them known in the American Journal of Medical Sciences in 1862. Cholesterine is a normal constituent of various of the tissues and fluids of the body-. It is found in the blood, liver (probably as contained in the bile), crystalline lens, spleen, meeonium, and in the nervous tissue in all parts of the body. It is also found in an altered condition. as stercorine, in the fecal matter, and as unchanged cholesterine in hibernating animals. It is naturally a crystalline solid, but in the fluids of the body- it is held in solution. For the form of the crystals, composition, and other characteristics, see CHOLESTERINE. This body is found in the largest quantity- in the substance of thc brain and nerves, and the blood coming from the brain contains a much larger percentage of it than is found in that coming from any other organ. From this and various other experiments, Dr.
Flint has demonstrated that cholesterine is a disassimilative product of nervous function, and that one of the offices of the liver is to separate it from the blood. He found among other things that it is produced in much greater quantity under active conditions, and that it is also produced in all parts of the nervous system. Sometimes the liver fails to separate it from the blood, when it collects, and produces a condition to which Dr. Flint has given the name cholestercemia, a species of blood-poisoning having an analogy to uremia, or blood-poisoning from accumulation of urea consequent upon disease of the kidney's. In regard to the glycogenic function of the liver, it may be stated that nearly all physiologists admit that Bernard demonstrated it completely, although for a long time many apparently well made experiments seemed to throw great doubt on the sub ject, sorne believing that the sugar found by I3ernard was a product of post-mortem changes. It is a fact that it is difficult to find sugar in the liver which may not be said to be produced after death; consequently, demonstrative experiments are exceedingly difficult. On examining the blood which comes from the lungs in animals upon which vivisection has been performed it is found to contain no sugar. Other experiments have left no doubt of the fact that, to serve some purpose in the animal economy, sugar is destroyed in its passage through the lungs, the most generally received view being that it is converted into lactic acid, which unites with the alkalies in the blood to form lactates, which again are converted into carbonates. It is thought that among the causes of the disease diabetes is an abnormal performance of the function of respiration (q.v.). The glycogenic matter of the liver, in composition, reactions, and particularly in its readiness to be transformed into sugar, has considerable resemblance to starch, and is called by some authors amyloid matter. On account of its insolubility in water it may be extracted from the liver after all the sugar has been washed out.