[A] The following questions have been much disputed: Is there a cystic and an hepatic bile? Is the one of a different nature from the other? Does their quantity increase or vary? &c. Contrary, and even opposite, opinions have been supported by numerous experiments made upon living animals, as Haller as well observed. These experiments, though at first sight contradictory, in reality are not so, as I have had the opportunity of convincing myself, by repeating them in the different stages of digestion, and during the abstinence of the animal, which previously had never been done with precision. The following are what I have observed in dogs that I have used in my experiments. (1) During abstinence, the stomach and the small intestines being empty, yellowish clear bile was found in the hepatic duct and ductus communis choledochus; the surface of the duodenum and jejunum were stained by a bile which had the same appearance; the gall bladder was very much distended by a greenish bitter bile, which was deeper in colour and more in quantity, according to the length of the abstinence. (2) During the gastric digestion, which may be prolonged for a sufficient length of time by giving the dog large pieces of meat, which he swallows without chewing, appearances were similar. (3) At the commencement of intestinal digestion, the bile in the hepatic duct was always found yellowish; that of the ductus communis choledochus deeper in colour; the gall bladder not so full, and its bile becoming already more clear. (4) Towards the end of digestion, and immediately after it, the bile of the hepatic duct, of the ductus communis choledochus, that contained in the gall bladder, and that which was spread over the duodenum, were exactly of the same colour as the common hepatic bile, a clear yellow, having but little bitterness. The gall bladder was but half full; it was not contracted, but flaccid.

These observations, repeated a great number of times, evidently prove, that such is the manner in which the bile flows during abstinence and during digestion. (1) It appears that the liver is continually separating from itself a sensible quantity of bile, which increases during digestion. (2) That which is secreted during abstinence is divided between the intestine, which is always found coloured with it, and the gall bladder, which retains it without transmitting any portion of it through the cystic duct, and where, thus retained, it acquires a deeper colour and a character of acrimony, necessary, without doubt, to the digestion which is soon to follow. (3) When the food, having been digested by the stomach, passes into the duodenum, then all the hepatic bile, which was before divided, flows into the intestine, and even in greater abundance; the gall bladder also pours that which it contains upon the alimentary pulp, and with which it is then found quite incorporated. (4) After the intestinal digestion the hepatic bile diminishes, and begins to flow, part into the duodenum and part into the gall bladder, where, being then examined, it is clear and in small quantity, because it has not yet had time either to become coloured, or to collect.

There is, therefore, this difference between the two kinds of bile, that the hepatic flows in a continual manner into the intestine, and the cystic, during the absence of digestion, flows back into the gall bladder; and whilst that function is going on it passes towards the duodenum; or rather it is always the same fluid, of which one part preserves the character it has when it leaves the liver, and the other part undergoes a change in the gall bladder. The difference of colour in the cystic bile, according to the time that it has remained in the gall bladder, is analogous to the colour of the urine, which becomes deeper as it is retained longer in its receptacle.

[B] The bile in the gall bladder, the urine in the bladder, and the semen in the vesicula seminales, are certainly absorbed; but it is not the fluid itself that re-enters the circulation, but only its finest parts, some of its principles that we are not well acquainted with, probably its aqueous or lymphatic portion. This does not resemble the absorption in the pleura and other analogous membranes, in which the fluid rejoins the blood in the same state as it left it.

[C] This is a necessary consequence of the disposition of the vascular system of the stomach. The arteria coronaria ventriculi superior being situated transversely between the stomach and the omentum, and furnishing branches to both, it is evident, that when the stomach, by separating the duplicatures of the omentum, lodges itself between them, and this in applying itself over the stomach becomes shortened, the branches that it receives from that artery cannot in the same manner apply themselves to it. To effect this it would be necessary, that they should proceed from the one to the other without the intermediate trunk that cuts them at right angles; then the stomach, by distending itself, would separate them in the same way that it does the omentum, and would lodge between them, instead of pushing them before it with their common trunk, and folding them upon themselves.