Cholesterine (Gr. bile, and firm, solid), or Biliary Fat, a non-nitrogenized organic substance, found in the bile and in other fluids or situations in the human body, or that of animals in which the biliary secretion is prominent, this substance when separately obtained having the appearance of spermaceti, and differing from ordinary fats only in the fact that it refuses to form a soap with caustic alkalies, even under the action of prolonged heat. Cbolesterine is neutral, inodorous, insoluble in water, soluble in ether and hot alcohol. Its composition is usually represented by the formula C25II22O. It is combustible and burns with a bright flame. It crystallizes in very thin, colorless, transparent, rhomboidal plates, frequently marked by a cleavage at one corner in a line parallel with the corresponding side, and often forming in layers, the borders of the subjacent plates showing very distinctly through those above. Cholesterine was discovered in 1782, by Poul-letier de la Salle, in biliary calculi; its presence in the blood was shown in 1830 by Denis. In a condition of health, cholesterine exists in the bile, blood, liver, brain and nerves, and the crystalline lens.
It is also found in very large quantity in the meconium, in the faeces of animals hibernating, and by some authorities it is said also in the faeces generally in health. It occurs frequently as a morbid deposit or product. Biliary calculi consist wholly of cholesterine, coloring matter, and mucus. The tablets of cholesterine are found in or obtained from cancerous growths, encysted tumors, and atheromatous deposits in the coats of the arteries, and sometimes as forming distinct deposits or tumors in the substance of the brain. Cholesterine is obtained also from the fluid of hydrocele, of ovarian cysts, of tubercle in the crude state, and from pus. Its quantity in the normal fluids is small, forming, according to Berzelius, 1 pnrt in 1,000 of the bile in man, and according to Prof. Austin Flint, jr., of New York, only .618 in 1,000. The analyses of the latter give as the proportion in 1,000 parts, for the venous blood of the male, .445 to .751; for the meconium, 6.245; for the human brain (in two instances in which death was sudden), 7.729 to 11.456. The bile and some other fluids can hold the cholesterine in solution, though by aid of what other constituent is not known; while it may perhaps exist, in organic union with other components, in the nervous substance and the crystalline lens.
While the chemical relations of cholesterine had been fully studied, its physiological relations long remained in doubt, or the subject at the most of conjecture. According to the researches of Prof. Flint, cholesterine is constantly forming in the system, being always present in the nervous matter and the blood, but by far the most abundant in the former; it is a necessary product of the waste of the nervous matter, and being removed thence in the circulation constitutes one of the most important of the materials to be excreted from the body. It is separated from the blood by the liver, appears constantly in the bile, and in this is poured into the alimentary canal. As in the case of urea, the most important excreted matter of the kidneys, so with cholesterine, if its separation and removal through the liver ceases, or is not in due amount, this product accumulates in the system, producing its form also of poisoning or deterioration of the blood, and leading to a corresponding class of diseases. Thus the bile has two distinct functions answering to the presence of two entirely distinct components in it.
One of these embraces the glyco-cholate and tauro-cholate of soda, which do not preexist in the blood, and so do not accumulate in it when the liver is torpid or its action arrested; these are produced in the liver, serve a useful purpose in completing the process of digestion, are not discharged in the fasces, and constitute a secretion only. The other function of the liver is the depuration of the blood by freeing it of excess of cholesterine; and to this end probably it is that secretion of bile continues in the intervals of digestion, though more abundant during the digestive acts. The ordinary fasces, according to Prof. Flint, do not contain cholesterine, but contain stercorine; the substance thus named by the author being invariably found by him in the normal faeces, and regarded by him as identical with that previously found in minute quantity (.02 to .025 part in 1,000) in blood, and named seroline. The transformation of cholesterine to stercorine occurs during the digestive process; and that it does not take place before digestion commences, nor when it is for the time arrested, accounts for the presence of the former only in the meconium and the excrement of animals hibernating. Stercorine is therefore the form in which cholesterine is discharged from the body.
The facts explain the distinction of the two types of jaundice. In the mild type the bile is formed, but its discharge being obstructed, its coloring matter chiefly is reabsorbed, and the disease is attended with yellowness of the skin, but is comparatively harmless; in the other, the grave symptoms and almost invariably fatal character are due to cessation of the action of the liver, with retention of cholesterine in the system. There is also a condition of the blood, which may or may not he attended with jaundice, due to a gradual and undue accumulation of cholesterine in that fluid, and to which Prof. Flint applies the name "cho-lesteraBmia." This can only occur when, through some organic or structural change in the liver, and not merely of a small part, but of so much of it that the remaining healthy portion, if any, is insufficient for the depuration of the blood, the organ is in consequence incapable of performing duly its excretory office.