lobule of a pig's liver. a. Duct with little sacculi in its coats. b. Small branches of the duct which are distributed upon the surface of the capsule: these are represented at least twice as wide as they ought to be. c. Inter-lobular branch of portal vein.

That the bile is formed in these cells and does flow along these biliary tubes, whether entering them by a free opening or by percolation through their walls, is a certain fact; but it is not known by what force the bile is propelled. Some have assumed it to be from the pressure of the full stomach upon the liver, but this notion is refuted by Bidder and Schmidt, who observed the contents of the gall bladder and the biliary tubes to begin to discharge rapidly in a cat some hours after a meal; their opinion is that it is by a contractile power of the tubes themselves, although they have not been able either to detect muscular fibres in them, or to succeed in making them contract by galvanism. And they attribute much importance to the descent of the diaphragm during respiration. The question, however, is by no means satisfactorily settled as yet, and demands farther investigation. The office of the gall bladder is obvious enough, being simply a reservoir of bile which is emptied into the intestines at a short interval after a meal. The bile collects in it after digestion ready for a recurring demand. In connection with the hepatic duct should be noticed a system of vessels accurately described by Weber of Leipzig, and named by him vasa aberrantia. They are most numerous at the transverse fissure of the liver, where they form an intricate net-work communicating with the larger branches of the biliary duct. By means of this vascular reticulation the ducts are connected with one another-they are, in fact, the anastomosing apparatus, and have been injected by Dr. Beale not only in the transverse fissure, but high up in the portal canals. They are thickly set with cocal pouches, which are probably not mucous glands, but, like those of the duct itself, little reservoirs of bile or gall-bladders in miniature.

Fig c.

Part of surface of an injected human liver, shewing the manner in which the vessels are distributed. The duct is not represented. a. Artery, of which only two small branches are represented. b. Branches of the portal vein. c. Branches of the hepatic vein. d. Part of the capillary network of a lobule.

The distribution of the hepatic vein is the converse of that of the portal. The portal divides in its course into diminishing branches and ends in capillary vessels. In these capillaries the hepatic vein takes its origin, and the smallest of its ramifications is larger than the extremities of the portal vein: thus from the first its special office of a collector, not a distributor, is indicated. Its position is about the centre of

the lobule; into it the blood from the portal vein is poured through the capillary vessels lying in immediate contiguity with the liver cells, so that in its passage from the portal to the hepatic vein it has a full opportunity of being subjected to their influence. The branches of the hepatic vein unite and enlarge as they proceed outwards to the circumference, and in some animals, as the seal, which require to abstain long from breathing, they form sinuses capable of containing a large quantity of blood, so as to prevent the gorging of the liver on one hand, and of the heart on the other. After uniting into large branches they pour their contents into the vena cava inferior, the largest vein in the body, which enters the right auricle of the heart, whence it is immediately passed on to the right ventricle, and from thence to the lungs to undergo further changes. What we may call hepatic blood then is to be found only in the hepatic veins, and in a diluted condition in the vena cava inferior.

Lymphatic vessels are met with in abundance in the portal canals and the transverse fissure, and materially contribute to the capacity of the liver for receiving a large addition to its fluid contents without inconvenience. Thus, for example, a pig's liver may be easily made to contain a quantity of water equal to its own weight, which may be injected from the portal vein.-(Beale.)

We have now described the mechanism of the liver, which may be rudely likened to a sponge placed between the stomach and the lungs, receiving the blood from the one organ and passing it on, after certain changes, to the other. To enable it to effect these changes, however, a supply of nervous force is required, and this it derives from two sources: one the cerebro-spinal, and the other the sympathetic. In the human subject this double origin is not easily demonstrated, for the cerebro-spinal nerve, the pneumo-gastric, is lost in the solar plexus on the right side, where it becomes blended with the great sympathetic, and on the left it is distributed on the stomach. In the dog and rabbit, however, the two pneumo-gastric nerves, after penetrating the diaphragm, give off distinct twigs, which accompany

Representing the cerebro-spinal axis and splanchnic nerves of a rabbit and shewing the relation of the nerves of the lungs, liver, &c. a. Brain. b. Cerebellum. cc. Spinal cord. d d. Trunk of the' pneumo-gastric nerves. e. Upper cervica

ganglion. f. Common trunk of the two pneumo-gastric nerves, reunited below the lungs. g. Inferior cervical ganglion. h. Filament of connection between the superior and inferior cervical ganglia. i. Cardiac filament of the pneumo-gastric. 3. Cardiac filament going from the first thoracic ganglion of the great sympathetic. mm. Filaments of connexion of the different ganglia of the great sympathetic with one another. 7. Thoracic ganglion. n. Filament of connexion between the spinal cord and the great sympathetic. o. Hepatic nerves going from the great sympathetic. p. Renal nerves going from the great sympathetic. qq. Ganglia of the solar plexus. r. Hepatic nerves going from the pneumo-gastric. s. Renal nerves. t. Hepatic nerves united. u. Olfactory nerves. v. Optic nerves. 2. Nerves of the third pair. y. Nerves of the fifth pair. 1. Heart. 2. Aorta. 3. Vena cava. 4. Portal vein. 5. Inferior vena cava below the renal veins, 6. Lungs. 7. Liver. 8. Gall bladder. 99. Supra-renal capsules. 10. Kidney. 11. Ureters.

the hepatic artery, and become lost in the intimate structure of the lobules.—(Bernard, p. 323.) We may fairly presume that they proceed as far as the capillary network and the secreting cells. It also receives branches from the diaphragmatic, which are distributed chiefly upon the walls of the hepatic vein. The explanation of the functions of the liver, both in health and disease, hinge so much upon the fact of the double supply of nerves, that we give a woodcut from Bernard's work in which it is shewn (from p. 322).*

Let us now enquire into the functions of the liver, or what changes the blood undergoes in its passage through its intricate net-work of vessels on its way from the stomach to the lungs. An obvious plan of commencing this enquiry, is to subject the two kinds of blood which we call the gastric and hepatic to a careful chemical analysis, so that the difference between them may be ascertained. This has been done by Professor Lehmann of Leipzig, whose paramount authority on questions of organic chemistry is universally acknowledged in the scientific world, and the result was communicated on the 12th of March, 1855, to the French Academy. As the matters this memoire embraces belong to science militant as distinguished from science dogmatic, it may be well to give a literal translation of the whole of Lehmann's short and satisfactory paper.

*For the whole of the facts and the wood-cuts contained in this paper we are indebted to the following interesting and important Works:

1st. On Some Points of the Anatomy of the Liver of Man and Vertebrate Animals, by Lionel S. Beale, M.B. Lond., 1856.

2nd. Leçons de Physiologie experimentale appliquée a la Médecine, faites au College de France, par M. Claude Bernard, &c., &c. Paris, 1855.

3rd. Die Verdauungssaefte und der Stoffwechsel. Eine physiologischchemische Untersuchung von Dr. F. Bidder und Dr. C. Schmidt, Professoren in Dorpat. Mitau und Leipzig. 1852.