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THE greater number of the photographs were taken from diagrams copied from the author's drawings. Many of them have been much diminished and some are less distinct than could be wished; but it is hoped that they will in some measure aid in rendering the description, more intelligible. The diagrams from which the photographs were taken, were copied from drawings which had been traced from the preparations with the aid of the neutral tint glass reflector. The magnifying power has been estimated by comparison with the original objects, but it is only to be regarded as approximative. The author feels that many of the delineations are capable of improvement, and since these have been finished he has been enabled to obtain photographs which convey a much more accurate idea of the structure represented, than he at first anticipated, especially in the case of tissues in a morbid state.

Fig. 1. FRONTISPIECE.-Plan of the arrangement of the tissues in a lobule of human liver. The part represented is supposed to be a small segment of a lobule, of which the centre is seen at e, and a part of the circumference on the left of the figure. At the lower part are seen branches of the vein, artery, and duct in a small portal canal.

Magnified about 120 diameters.

p. v. Portal vein.

a. Artery.

d. Duct.

e. Hepatic vein.

The branches of the portal vein, interlobular, are seen in the upper and lower part of the figure breaking up into capillaries, which form a solid network throughout the entire lobule. In the meshes of this network are con

tained the tubes of the cell-containing network. A part of the capillary network is isolated at b, and a portion of the cell-containing network at c. As the portal capillaries converge towards the central part of the lobule, the meshes of the network become elongated, as shown at ƒ, and at length the capillary vessels open directly into the small intralobular vein e, which carries the blood away from the lobules. Numerous branches of the artery may be traced on the left of the figure pursuing a somewhat tortuous course amongst the other vessels at the circumference of the lobule, and with care a few small branches may be followed which open at length into the portal capillaries near the margin of the lobule, as shown at g. It will be observed that the diameter of the smallest arterial branches is considerably less than that of the venous capillaries into which they open. The branches of the duct may be known by their epithelial lining, and may be followed amongst the divisions of the other vessels passing into the lobule. The very narrow ducts are seen to be continuous with the tubular network in which the liver cells lie. The direct continuity of the narrow efferent duct with the wide secreting tubular network which contains the liver cells is shown at c and in other situations. At f a distinct interval is seen between the walls of the capillaries and the delicate membrane composing the tubes of the cell-containing network, the meshes of which, like those of the capillaries, become much elongated in this part of the lobule. The liver cells situated near the margin of the lobule contain many oil globules, which are not visible in those occupying a more central position.

This drawing is to be regarded as a plan which embodies the results of actual observations made upon many different specimens. It is supposed to be magnified about 120 diameters.

Fig. 2.-Part of surface of an injected human liver, showing the manner in which the vessels are distributed. The duct is not represented.

a. Artery, injected with vermilion, of which only two small branches are represented.

b. Branches of the portal vein, injected with white lead.

c. Branches of the hepatic vein, injected with lake.

The manner in which the portal vein, artery, and duct alternate with branches of the hepatic vein is well seen. In the upper part of the figure, at d, part of the capillary network of a lobule is represented. The two small white vessels are branches of the artery, which are seen to open into the capillaries near the portal surface of the lobule. The drawing was made with the aid of the neutral tint glass reflector.

Magnified about 16 diameters.

Fig. 3.-Thin section of several lobules of the human liver, showing the general arrangement of the ducts and branches of the portal vein, as they lie in the interlobular fissures.

a. Branches of the portal vein, injected with white lead.

b. Small branches of intralobular vein, injected with lake. At c some of the capillaries of the lobule are represented.

d. Branches of the duct, injected with Prussian blue, ramifying in the interlobular fissures, and giving off but few branches in their course towards the lobules.

The imperfect manner in which the lobules are mapped out in the human

subject, and in most mammalian animals, is shown in this figure. Drawn with the neutral tint glass reflector.

Magnified about 13 diameters.

Fig. 4.-Portal vein, artery, and duct at the margin of a lobule of the human liver. A small branch of the vein is represented at a. The branch of the artery may be known by its much straighter course than the branches of the duct, which are seen to be very numerous in this figure.

Magnified 20 diameters.

Fig. 5.-Transverse section of a very small portal canal.

a. Portal vein.

b. Branch of duct, encircling the vein, and giving off branches. Between the vein and duct, a section of the artery is seen.

Magnified 20 diameters.

Fig. 6. Very curious anastomosis between small branches of hepatic vein in the human liver, injected with lake. Small vessels are seen opening into the trunks upon all sides.

Magnified about 35 diameters.

Fig. 7.-Interlobular branches of artery partially encircling a lobule of pig's liver. Branches from either side are seen passing off to be distributed to adjacent lobules. Many of the small branches anastomose, and thus an arterial network is formed. At b a few of the portal capillaries are represented, and several small branches of the artery are seen to open into them. Magnified 42 diameters.

Fig. 8.-A small branch of the artery, showing a portion of the network formed by the anastomosis of many of the smallest branches.

Fig. 9.-Two small branches of artery on either side of a branch of duct.— A network is formed upon its coats.

Magnified 10 diameters.

Fig. 10.-Interlobular branches of portal vein of the pig's liver.

From either side are represented branches to the contiguous lobules which break up into the capillaries of the lobule; the latter are only partially injected in this specimen.

Magnified 42 diameters.

Fig. 11.-Distribution of the duct upon the surface of a very small lobule of the 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. Interlobular branch of portal vein.

Magnified 42 diameters.

Fig. 12.-Interlobular branches of vein, artery, and duct of pig's liver. a. Portal vein, injected with chromate of lead.

b. Hepatic duct, injected with Prussian blue.

c. Artery, injected with vermilion.

d. Small branch of the duct, which passes through the capsule of the lobule, to be distributed in the interior.

Magnified 35 diameters.

Fig. 13.-Interlobular branches of the artery and duct of the pig's liver. e. Artery, injected with vermilion.

f. Duct, injected with Prussian blue.
Magnified 15 diameters.

Fig. 14.-Distribution of interlobular ducts to several adjacent lobules upon the surface of pig's liver, the margins of which are shown by dotted lines. At g, and in several other points of the preparation, the injection has passed into the cell-containing network of the lobule, in consequence of which the confused appearance, represented in the drawing, results.

Magnified about 16 diameters.

Fig. 15.-Ducts with vasa aberrantia, injected with Prussian blue, from

the transverse fissure of the human liver.

Natural size.

Figs. 16, 17.-Ducts and vasa aberrantia from the transverse fissure of

the human liver.

Half the natural size.

Fig. 18.-Dilated portion of a duct, also from the transverse fissure, giving off long straight branches, which pass off to the secreting structure. The irregularity of outline of some of the larger branches of the duct in this situation is shown at c.

Magnified 8 diameters.

Fig. 19.-A part of fig. 16, magnified 4 diameters. The irregular branches of the vasa aberrantia are seen in this figure anastomosing freely with each other, and forming a lax network; at e, the trunk gives off a smaller branch. Branches are observed coming off from all parts of the circumference of the larger ducts in this situation.

Fig. 20.-Interlobular duct with lateral appendages and irregular branched ducts, or vasa aberrantia. The greater number of the lateral channels do not project beyond the outer surface of the fibrous coat of the duct a. In the human liver the orifices of these channels form a straight line on opposite sides of the ducts.

b. A smaller branch with numerous sacculi not projecting beyond the fibrous coat; as this branch becomes narrower and less sacculated its coat is seen to become much thinner.

Figs. 21, 22, 23.-Portions of interlobular ducts.

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