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and rupture of its coats has not taken place, the fluid which escapes from the hepatic vein will not have the slightest blue tinge; but if this should be the case, we may still proceed, as it often happens that, although extravasation has occurred from the duct into the vessels, the escape has only taken place into one of the smaller branches; and as the vessels do not anastomose, it only affects the lobules supplied by the branch of vein in which the opening has been made.

When size runs out at the hepatic vein, the open end of the latter may be tied, and a little more carefully injected into the portal vessels, in order to distend the capillary plexus. Lastly, a little size is injected into the duct, in order to distend the larger ducts, and to prevent the injection from returning after it has been forced into the smaller branches. When the liver appears filled, it may be placed in cold water until the size sets.

By varying the plan above described somewhat, the different vessels may be injected with different colours. I have succeeded in injecting a human liver with four colours. The portal vein is injected with Flake White, the artery with Vermilion, the hepatic vein with Lake, and the duct with Prussian Blue. From this liver I have obtained specimens which show very clearly many of the points which I shall describe, and many of these preparations have been preserved. In this liver, as would be supposed, it is difficult to find a part in which the vessels and ducts are well injected, but such specimens have been obtained.

PREPARATION OF SPECIMENS PREVIOUS TO EXAMINATION IN THE MICROSCOPE.

When the ducts and portal vein have been successfully injected in the manner described, the greatest care is required in preparing the section for examination. A very sharp knife, or Valentin's knife, in good order, may be employed. The thinnest section, after very careful washing, must be placed in a drop of syrup, or glycerine, and the glass cover so applied as to press very slightly upon the specimen. If the washing be not carefully conducted, the superficial cells will be removed, and the vessels will collapse. On the other hand, if all the cells and debris adhering to the surface of the section are not washed off, the preparation will

appear confused and indefinite. The sections should bear examination with a quarter or eighth of an inch object-glass.

It is, of course, very difficult, and, in great measure, a matter of chance, to obtain a section including the course of the smallest duct, and it will often be necessary to examine very many sections before a demonstrative specimen can be obtained. When we consider how difficult it is to obtain a section of the mammalian kidney, showing, even for a short distance, the convolutions of a single uriniferous tube, it need not excite surprise that it is rare to obtain a section of the liver, which shows clearly the termination of the smallest branches of the duct, for these tubes in passing only a very short distance, often occupy many very different planes. The circumstances which render the demonstration of the course of the uriniferous tube very difficult, operate still more forcibly in the case of the liver, as the tubes are very much smaller, the tissue of which they are composed infinitely more delicate, and the entire organ so soft that very slight manipulation is sufficient entirely to destroy the relative positions of the anatomical elements of which it is composed.

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CHAPTER II.

GENERAL DESCRIPTION OF THE LIVER.-DIMENSIONS.-BULK.

WEIGHT.-SPECIFIC GRAVITY.-CHEMICAL COMPOSITION.-
PORTAL CANALS.-HEPATIC VENOUS CANALS.-LOBULES OF
THE PIG AND OF OTHER ANIMALS.-CAPSULE OF THE LO-
BULES. PORTAL CANALS AND INTERLOBULAR FISSURES.-
GLISSON'S CAPSULE.-MANNER IN WHICH THE MAPPING OUT
INTO DISTINCT PORTIONS IS PRODUCED.

FOR much that is known of the anatomy of the liver, we are indebted to the labors of one of the greatest living anatomists, Mr. Kiernan, and almost every one is well acquainted with his most valuable researches upon the structure of this gland.* These investigations were made nearly a quarter of a century ago, at a time when the compound microscope was a very imperfect instrument, and principally with the aid of a lens alone. The liver-cells, the great agents in the secretion of bile, were hardly known, and the exact arrangement of the capillary vessels was not satisfactorily demonstrated until many years after. Yet very much of of that which Mr. Kiernan did, and the correctness of the conclusions which he arrived at, have been fully confirmed by later investigators. The latest researches appear to militate most strongly against the inferences of Mr. Kiernan with reference to the manner in which the ducts commence; but there is, I think, little doubt, that he was, in the main, right, and the conclusions which I have arrived at in investigating many of my own preparations were foreshadowed by him at a time when the means of observation were very imperfect in comparison to those which we may now employ.

Dimensions, Weight, and Chemical Composition of the Healthy Liver. The liver in health measures about 12 inches from side to side, and 6 or 7 in its antero-posterior diameter. Its bulk corresponds to nearly 100 cubic inches, and its weight varies from 3 to 4 pounds, according to the quantity of blood which it may contain

* On the Anatomy and Physiology of the Liver. Phil. Trans. 1833.

at the time it is examined. Its specific gravity in health is about 1.05.

The following is an analysis of a liver presumed to be healthy. The organ was taken from the body of a man 31 years of age, who was killed by falling from a second-floor window while in the enjoyment of perfect health.

[blocks in formation]

Per 100 of
Solid Matter.

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In disease, the proportion of these constituents is liable to very great variation. In fatty degeneration an enormous amount of fatty matter may accumulate in the organ. In one remarkable

I obtained from a liver 75.07 per cent. of solid matter, and of this 65.19 consisted of fatty matter.* In scrofulous degeneration of the liver, the albuminous materials and the water are increased, while the fatty matter is diminished in quantity.

The liver is essentially composed of certain elementary structures, which are common to all secreting organs possessing ducts, although in the different glands these structures are variously modified to serve special ends, which differ in each individual organ. These essential structural elements are the following:-Cells, lying in a cavity composed of basement membrane, which have the power of separating certain peculiar substances from the blood, for which alone they have any attraction. Vessels, which bring the blood into close proximity with the cells, and Efferent Ducts, in direct continuity with the cavity in which the secreting cells are contained, which carry off the secretion after it has been elaborated.

It is impossible to help being forcibly struck with the manner in which these anatomical elements are arranged in this organ, for the same disposition of the parts which economizes material and

* Diseases of the Liver. Dr. Budd. Second edition.

space in the greatest possible degree, provides for the most complete and perfect action of the cells upon the blood. While the latter fluid is made to pass slowly through an extensive series of tortuous channels, it is only separated from the cells by a delicate membrane of extreme tenuity, through the intervention of which it bathes the greater part of the surface of each individual cell.

In the liver the capillary network is of a very unusual extent, a circumstance which alone would lead us to infer that the change exerted upon the blood as it passes through the organ is of a very important nature, and one which must be effected completely. The system of efferent ducts is extensive, and their course before they make their exit from the organ, a very intricate one. The coats of the larger ducts are largely supplied with arterial blood, and the arrangement of vessels around all of them is peculiar.

Portal Canals and Hepatic Venous Canals.-In the compact mammalian liver there are two important series of channels, which in their ultimate distribution may be said to alternate with each other (fig. 2). Of these, one set contains branches of the portal vein, hepatic artery, and hepatic duct, while the other series contains branches of the hepatic vein alone, with the vascular branches which are supplied to their coats. Such an arrangement permits of a very equable and free distribution of the blood to the capillaries of the individual lobules, of which the organ is made up, and promotes its rapid removal after the proper changes have taken place in it; while at the same time the carrying off of the bile after its elaboration is effectually provided for, and the occurrence of other changes in it during its course to the gall bladder and common duct is facilitated. Upon the under-surface of the liver is a large groove, the longitudinal fissure, from which passes off transversely upon the surface of the right lobe another depression, the transverse fissure. At this point the portal vein, the hepatic artery, and nerve-fibres, enter the substance of the organ; and the hepatic duct and numerous lymphatic vessels emerge from it. These structures all lie in close proximity to each other, and, in the larger channels, are bound together by a certain quantity of areolar tissue.

From the transverse fissure may be traced numerous tubular passages throughout the entire substance of the liver, those most

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