Its saponaceous nature was said to assist the union of the oil and water in the formation of chyle; but this idea is effectually destroyed by the experiment of Dr. G. Fordyce. who tied the ductus choledochus communis, and still found the lacteals filled with a chylous fluid.
The ancients supposed the liver to be the organ by which the nourishment was prepared; and Fourcroy has lately endeavoured to revive the opinion, supposing that the long protracted circulation was destined to unite more intimately the molecules of the blood with the new nourishment, with the air taken in by the lungs, and that formed during the circulation. When we reflect on the general importance of the liver, and that its place cannot be supplied by any other organ; when the emaciation which follows its diseases, and the immense size to which inactivity with highly nutritious food enlarges it, this idea will appear to have greater force. Yet we think it acts only, in this respect, a secondary part. We shall find, in our enquiries into the process of digestion, a very great change produced by it on the food taken in; an immense distance between, for instance, the herbage of the field and the muscular fibres of the sheep and ox: we shall, of course, perceive the necessity of a powerful agent for the production of this change. A fluid highly animalised, is necessary to join the vegetable matter before it is permitted to mix with the general mass; for the mildest chyle immediately injected into the vessels is fatal: and this matter must be very distant from a putrescent fluid, since this process, already going on in the sanguiferous system, requires a check rather than a ferment. It is then a fluid necessary for perfecting the assimilation of the aliment, and giving to the chyle some principle which enables it to join the general mass with impunity. We consequently see it formed from blood which has undergone a languid circulation, but not from those parts where it might meet with a putrid fomes; for the hae-morrhoidal veins do not form a portion of the vena por-tarum. This blood is said by some authors to be peculiarly fluid; it probably contains a larger portion of soda, with hydrogen and carbone. The two latter, in consequence of the languid circulation uniting with the remaining oxygen, form with the fibrin of the blood the oil, which is rather a spermaceti than a truly oleaginous fluid. In those animals whose respiratory organs are small, the liver is unusually large; and we find birds, whose livers are naturally small, when pent up in a close coop, have this gland considerably increased in bulk. When this oil abounds and the fluid no longer holds it in solution, a crystallization takes place, and biliary calculi are formed, of which we shall afterwards treat. See Calculus biliaris.
It is observed, in general, that the gall of small animals is stronger and more acrid than those of larger kinds; that the gall of carnivorous animals is more active than those of herbivorous. Instances are those of the hawk, serpent, eel, and pike, but in general all their secreted fluids are more acrimonious.
Physiologists have warmly contended, whether the bile was derived from the hepatic artery or the vena portae. But, as the former artery is small, as its ramifications are not peculiar, and as the circulation in the latter is singularly complicated, and has no apparent object but the preparation of a very important fluid, it is generally supposed that the hepatic artery only nourishes the viscus, while the secretion is exclusively from the contents of the vena portae.
The changes of the bile from disease are not numerous, but merit particular notice. We have introduced the appearances which putrefaction really occasions, to show that this state of the bile is often accused, when in reality it does not exist. The dark acrimonious bile is often a depraved secretion; and the dark flakes in bile are equally produced by a derangement in the functions of this organ. These are generally the result of too great indulgence in spirituous liquors. Bile will sometimes assume so dark a hue as to be mistaken for blood. Dilution destroys the error; for the diluted fluid has a yellow tinge; and the flakes, to which this dark colour is often owing, are then obvious. With acids the bile assumes a greenish colour; and, as bile when in the circulating system is soon carried to the kidneys, we once saw it convey this green hue to the urine. . The cause was evident, since an alkali destroyed it. Another disease of the bile is an oiliness; in other words, the adipocire heroines a more perfect oil, which the soda does not unite to the watery part of the fluid. It is often vomited in this state, and is the strongest proof of a considerable injury experienced in the process of digestion. The defect of bile is known from the white colour of the stools; but more certainly from the appearance of bile in the urine and under the skin. We see occasionally the kidneys torpid from a paralysis of the renal vessels, but we recollect no instance of a want of bile from the same cause. Fernelius, in his Pathology, speaks of a defect of bile as producing different diseases; but he means rather an obstruction, and that kind which is owing to a scirrhous liver.
In fevers the bilious discharges are often copious and troublesome; and the liver is the organ generally affected when the fluids are not propelled to the surface, since its vessels chiefly contain the blood from the venous system. Yet copious discharges of bile are peculiar to remittents and intermittents, though in continued fevers of every kind the liver is unusually filled - K k in medical language infarcted - and peculiar attention, to the discharge of its contents is required.
According to the supposed uses of the bile has it been employed as a medicine. It is a saponaceous aperient, a stomachic, a laxative, or a tonic, if the opinion of the author is in favour of either system. When the bile is deficient, it has been supplied with that of the ox; the practitioner forgetting that bile in the stomach was the source of numerous inconveniences, particularly sickness, faintness, and cold sweats. It has, however, been fortunately given in pills, and escaped the stomach without greatly disordering it. That bile is a stimulus to the action of the intestines is more probable; yet in jaundice we have not found costiveness peculiarly prevalent, and it seems to have been marked as a symptom rather from theory than observation. Inspissated bile of oxen has been given to children in a dose of one grain, and to adults in three or four, three or four times a day, to relieve visceral obstructions, to promote urine, and the menses; or half a drachm has been administered in clysters. If this has not succeeded, Boerhaave recommends the gall of the eel or pike; and remarks that the hard bellies of rickety children have been relieved by these remedies. We cannot doubt the utility of such an acrid fluid; but the small proportion of an ox's bile above recommended can have very little effect. If it has any, we cannot think that it would be a salutary one. In jaundice it has been given to supply the defect of bile; but modern practice disregards it, and we cannot speak of it from experience. On recurring to those authors who have recommended it, we find those vague and general praises which in similar circumstances we have had so much reason to distrust.
As putrid, acrimonious, and copious discharges of bile from the intestines are so often accused as causes of disease, when in reality they are only effects or symptoms, so in the stomach it is often supposed to be injurious, when brought by the medicines intended to discharge it. When bile is suspected of producing inconvenience in the stomach, and an emetic is given to discharge it, we often find no bile evacuated, but the next food or medicine brings it up; in fact the fluid, which the emetic, by inverting the action of the duodenum, had brought into the stomach.
A too copious secretion of bile sometimes occasions inconvenience, and in this case the alternation of laxatives and opiates removes the cause of complaint. We have thought that opiates really check the secretion of bile; but as any stimulus on the mouth of the opening of the ductus communis will increase the discharge, opium may act only by diminishing its too great sensibility and irritability. We may just add, that, in judging of the pains occasioned by accumulations or obstructions of bile, we must recollect that the under edge of the gall bladder, and the entrance of the biliary duct, are nearly at the pit of the stomach; the pain is felt there when a stone enters the duct, and a fulness is perceived in that part when there is an accumulation of bile. The course of the duct is then backward; and when the stone is near the extremity of the duct which opens into the duodenum, the pain is felt on the opposite side at the back.
Haller's Physiology, in the chap. on the Liver. Per-oival's Essays Med. and Exp. Fordyce's Elements of the Practice of Physic,part. i. Macbride's Experimental
Essays. The Appendix to Sir John Pringle's Diseases of the Army. Maclurg on the Human Bile. Coe on Biliary Concretions. Saunders on the Structure, Economy, etc. of the Liver; and Fordyce on Digestion. Fourcroy Systeme de Connoissances Chimiques. Cadet Experiences Chimiques.