mass, and containing within its meshes the cap-
illary network. In the fresh state the liver-cells
appear as spherical or egg-shaped bodies, usu-
ally presenting facets. They are somewhat flat-
tened by being pressed against one another (Fig.
83). Corpuscles possessing processes are some-

times found. &* nucleus;' ft, with

double nucleus. Prey.

Hie hepatic cells are about 0.0130.02 mm.
in diameter, and possess one or two nuclei, 1 which are gener-
ally spherical, although they occasionally appear to be flat-
tened ; the diameter is 0.0060.007 mm. The liver-cells do
not possess any membrana propria, but a hardened boundary
layer seems to exist in its place. It is probable also that the

1 Occasionally three or five nuclei, especially in young subjects (Beale).




190 MANUAL OF HISTOLOGY.

cells are bound together by a colloid substance, although this
is a point which has not yet been definitely settled.

Sections of a dog's liver, immersed for a short time in dilute osmic acid, will
occasionally exhibit a brown or black tracing between adjoining cells. Pres-
sure on the cover glass will part them and leave the darkened material free in
the field of vision. I have satisfied myself that this tracing is not of a nerve,
biliary duct, or connective-tissue fibril ; it is either a portion of the boundary
layer of a liver-cell, or, as I suppose, a colloid substance between two cells.
This appearance, however, is not constant.

The protoplasm is of a dark brownish or greenish color. It
is viscid, and contains numerous granules of small size, in ad-
dition to smaller or larger fat-droplets. 1 In livers hardened by
chromic acid or alcohol, the shrinkage of the cells causes them
to appear polyhedral, and they also seem much darker than in
the fresh state. If the portal or hepatic vein has been injected,
the cells will show distinct indentations produced by the dis-
tended capillaries.

When liver-cells are treated with diluted acetic acid, their
protoplasm becomes pale, while their nuclei are rendered more
conspicuous. In a dilute solution of caustic potassa the cells
swell up, become rounded, and are finally dissolved. With
water they also swell up, become paler and more rounded, and
at length disintegrate. In the fresh state, by the addition of
an indifferent fluid ( per cent, solution of chloride of sodium,
or iodized serum), the liver-cells are said to show protoplasmic
movements. The granular substance of the liver-cells has
been shown (by Schiff, in frogs, and by Nasse, in certain mam-
malia) to consist of an animal amylum, which is converted into
sugar through the agency of a peculiar ferment.

The fat-droplets may be either small in number and size or
quite numerous and large. Not infrequently they coalesce to
form larger fat-globules. In the so-called fatty infiltration they
are very large, and compose the greater part of the cells. The
nuclei are granular, and where two or more of them occupy
the same cell, they may apparently be united to each other.

1 According to Kupffer and Klein the substance of the cells is composed of a
honeycombed network, i.e., an intracellular reticulum. Klein says the nucleus is lim-
ited by a thin membrane, and includes an intranuclear network, containing occa-
sionally one or two nucleoli. The intranuclear network is in continuity with the
intracellular one, and the network of contiguous cells are in connection with one
another (Klein and Smith : Atlas of Histology).



THE LIVER AND BILIARY APPARATUS. 191

Division of a nucleus, as described by Kolliker, I have never been able to
confirm. When two nuclei are placed in contact, there may be an appear-
ance of division, but the actual process is not easy to see.

Thin liver sections may be stained either in carmine fluid or
luematoxylon, and preserved in glycerine or balsam.

The larger bile-ducts. If, for the sake of convenience, we
imagine that the hepatic duct enters the liver to be distributed
to its substance, we may describe it as giving off two primary
branches at the transverse fissure, one passing to the right
lobe, the other to the left. As these branches continue their
course, following the subdivisions of the hepatic artery and
portal vein, they also undergo successive divisions, and at
length enter the interlobular canals. In this position their
diameter varies between 0.02 and 0.03 mm.

The primary branches do not, however, pass unchanged
into the liver tissue. They ramify even before entering- the
gland, but such vessels are distributed only to the under
surface (Henle). Other biliary ducts, given off in the trans-
verse fissure, form a network on the upper surface, as may be
demonstrated by injecting the hepatic duct with carmine-gly-
cerine. The branches of these networks then enter the liver-
tissue and ramify throughout it, following the subdivisions of
the hepatic artery and portal vein.

As the divisions of the hepatic duct diminish in size, the
thickness of their walls undergoes proportionate diminution.
The trunk of the hepatic duct comprises an internal layer
measuring 0.15 mm. in thickness, and an external layer of 0.2
0.3 mm. Both of these coats are composed, according to
Henle, of interlacing connective-tissue bundles, in which elas-
tic fibres are freely intermixed. These ducts have an internal
lining of cylindrical epithelium, which is 0.05mm. in height.
Even where the branches measure only 0.2 mm. in diameter
they have cylindrical epithelium surrounded by a single layer
of connective tissue longitudinally disposed, in which there
are also muscle-corpuscles, distinguished by their long, rod-
shaped nuclei (Heidenhain). The most minute biliary pas-
sages consist of a structureless membrana propria, which is
lined with flattened cylindrical epithelia.

Glands of the ducts. In the trunk of the hepatic duct and
its subdivisions, down to those branches of which the diameter
is not less than 0.5 mm., the mucous membrane is provided



192 MANUAL OF HISTOLOGY.

with numerous irregular excavations, measuring 0.15 0.3 mm.
in their long diameter. In this trunk there occur also a great
number of pores or orifices, which, on examination, prove to
be the mouths of the passages leading from simple and com-
pound gland -like bodies, the so-called glands of the bile-ducts.
The simple glands consist merely of single vesicles, or alveoli,
with afferent passages, all of which are imbedded in the mu-
cous membrane ; or of two or more vesicles with a single pas-
sage. The compound glands are formed by the union of two
or more simple ones, which have a common passage. The} 7 " are
quite large, and their expanded portions lie on the outer sur-
face of the hepatic duct. When filled by injection with gela-
tine they are visible to the naked eye. The passages pierce
the walls of the duct at an acute angle, pursuing a course
within its walls, nearly parallel to the duct itself ; the opening
into the mucous membrane is therefore quite a distance from
the gland-vesicles. According to Henle, these compound glands
are not found in the larger branches of the hepatic duct, but
they occur frequently in the network of bile-ducts situated
in the transverse fissure. Allusion has already been made to
them. The vesicles measure 0.04 mm. in diameter, and, like the
excavations in the larger branches of the duct, are lined with a
cylindrical epithelium, in no way differing from that of the
duct itself ; the afferent passages also possess the same kind
of epithelium.

Structures allied to these excavations and glands occur in
small number in the bile-ducts ' which are found in the liga-
mentum triangulare and on the diaphragm, where they appear
as villous prominences on the duct- walls.

According to Theile, Weber, and others, these bile-ducts represent the last
vestiges of an atrophied liver substance, the existence of which dates back to
infancy, or perhaps to fetal life.

The excavations in the larger branches are either simple
diverticula of the internal walls, or the openings of lateral bile-
ducts ; the punctate pores are the orifices of the outlet pas-
sages of duct-glands.

Capillary bile-ducts .When the larger bile-ducts, by con-



1 Vasa aberrantia of E. H. Weber.



THE LIVER AND BILIARY APPARATUS'. 193

tinuous subdivision, have at length reached the interlobular
canals, in conjunction with the branches of the portal vein and
hepatic artery, they send capillary branches within the sub-
stance of the lobule, and thus form an intralobular network.
These capillary ducts are of extreme delicacy, measuring only
from 0.001 to 0.0012 mm.

In order to demonstrate them fully they should be filled by
natural injection. The substance to be employed for this pur-
pose is a solution of pure indigo-carmine. The animal serving
for injection (rabbit or dog) should be secured in the manner
described in the chapter on the Kidney, where all the neces-
sary manipulations are fully detailed. The best results are
obtained by injecting a cold, saturated solution of indigo-
carmine into the external jugular vein, directing the stream
toward the periphery (brain) ; 5 or 10 ctgms. are to be injected
at intervals of thirty to forty minutes, and the injection con-
tinued until from 25 to 50 ctgms. have been used, the amount
varying according to the size of the animal. It takes a longer
time for the elimination of indigo-carmine through the capillary
bile-ducts than for the same process by way of the renal tubules,
and a larger amount of solution will therefore have to be em-
ployed. As soon as large quantities of the indigo solution have
been injected into the jugular vein, the animal becomes uncon-
scious and there is a decrease of temperature ; hence, it should
be covered over with layers of cotton-batting. After a variable
time (three to twelve hours) the animal is killed in the follow-
ing manner : The abdomen is opened and the canula of a large
syringe filled with absolute alcohol secured in the lumen of the
portal vein ; the inferior vena cava is then cut across above the
entrance of the hepatic vein, and the piston of the syringe
pushed home. The liver, which before was of a uniform blue
color, -now presents a marbled appearance, not unlike that of
malachite.

Or, the portal vein may be injected with the writer's carmine-
glycerine, the vena cava having been divided as above. In
either case the liver is to be removed at once and placed in a
vessel containing absolute alcohol, and while immersed in that
fluid cut into small fragments. Sections may then be made in
a few hours.

The arrangement of the bile-capillaries differs in different
animals. In the rabbit, for instance, they lie between the ad-



194



MANUAL OF HISTOLOGY.



joining surfaces of two contiguous cells, and rarely in the
canals formed by the edges of three or more cells (Hering '). So
that while the blood-capillaries occupy the canals previously
described, the bile-capillaries form an independent network be-
tween the boundary surfaces of the liver-cells (Figs. 84 and 85).
In cross sections they may be seen, appearing as small, circular




FIG. 84. FIG. 85.

FIGS. 84 and 85. Injected liver of rabbit. The narrow, reticulated bile-capillaries are shaded with
[longitudinal, the broader blood-capillaries with transverse lines. Within the boundary line or septum of
two contiguous cells the cross-section of a bile-capillary is seen as a dark spot or point. The liver cells
contain one or two nuclei. In Fig. 84, the bile-capillaries are slightly distended by the artificial injec-
tion ; in Fig. 85, markedly so. Hering.

openings between the cells, while in longitudinal sections they
present a linear arrangement (Figs. 85 and 86). In the dog
this arrangement is the same, only here the bile-capillaries
occur more frequently in the canals formed by the edges of the
lower cells.

According to Hering, both in rabbits' and dogs' livers the blood-capillaries
are separated from the bile-capillaries by the intervention of at least one liver-
.cell. Livers in which the bile-capillaries have been injected by the natural
method with indigo -carmine do not always demonstrate this. And here it may
be remarked, that in artificial or forced injections of the bile-capillaries they
are always distended beyond their natural diameters. 3

1 Hering : Ueber den Bau der Wirbelthierleber, and article on Liver in Strieker's
Manual.

2 Compare Figs. 84 and 85, after Hering. Even in Fig. 84 the bile-capillaries are
larger than they ought to be. In an article on the liver by Dr. W. G Davis, in the
Amer. Jour. Med. Sci., Vol. LXXVIII., the distention of the capillaries is excessive.



THE LIVER AND BILIAEY APPARATUS.



195



By conjoined natural injection of the bile-capillaries and
artificial injection of the portal system with carmine-glycerine
by the methods above detailed, very gratifying results are ob-
tained. Care must be taken,
however, not to use too much
force during the process of in-
jection, and only such por-
tions of the liver should be
chosen for sections as show,
by their red color, a perfect
filling of the portal branches.

While the elimination of
the indigo-carmine is taking
place within the liver of the
living animal, the bile-capilla-
ries probably contain the salt
in a soluble form. The addi-
tion of absolute alcohol at
once precipitates this color-
ing reagent in the form of
exceedingly fine stellate crys-
tals, or as finely granular mat-
ter, which may in some meas-
ure account for the angular
character of the biliary capil-
laries, as seen in such specimens. Gentle curves, such as are
represented in Fig. 85, never appear. The constringing action
of the alcohol on the liver-cells has unquestionably some effect,
and therefore modifies the normal appearance.

Natural injections further show the great preponderance of
the biliary- over the blood-capillaries. In the liver of a dog,
for instance, each liver-cell seems suspended within two or
three (rarely four) bile-capillaries, and where the latter are




PIG. 86. Liver of a three-months' child, hard-
ened in chromic acid. The capillaries are filled with
red blood-corpuscles (indicated by colorless rings) and
a few leucocytes. The cross section of a bile-capillary
is shown within the boundary line of any two con-
tiguous cells. A similar cross section is shown in
the canal formed by three adjoining liver-cells.



One need only compare Fig. 3 in Davis's article with Fig. 84 of Hering's, which, by
the way, is a good illustration.

The first to describe the intralobular network of bile-capillaries were Andrejevic
(Ueber der feineren Bau der Leber. Wiener Sitzungsbericht, 1861) and MacGillavry
(Zur Anat. d. Leber. Wiener Sitzungsbericht, 1864). Chronszewski was the first to
inject the bile-capillaries by natural injection (Virchow's Archiv, Bd. 35). MacGillavry
Chronszewski, Budge, and others, described the bile-capillaries as possessing true
walls.



196



MANUAL OF HISTOLOGY.




FIG. 87. Capillary bile-ducts of a rabbit,
distended by artificial injection : 1, a portion
of a lobule ; or, central vein ; 6, 6, interlobular
veins ; c, c, bile-ducts ; d, d, blood-capillaries ;
e, e, bile-capillaries.



joined together the calibre of the capillary is markedly in-
creased. Sections made parallel to the external surface of the
liver, immediately under the capsule, generally cut the central

vein transversely, and such sec-
tions show that the bile-capillaries
possess a somewhat radial course
(Pig. 87). Human livers can rarely
be obtained in a fresh state, and
examinations of their bile-capil-
laries are therefore attended with
difficulty.

Do the bile-capillaries possess
walls of their own f This ques-
tion must be answered in the
affirmative. In specimens where
the bile- capillaries have been in-
jected by the natural method,
cross sections of such capillaries
will demonstrate, with high pow-
ers, that there is a dot of blue indigo-carmine surrounded by
a distinct circle which is perfectly transparent and in marked
contrast to the somewhat yellowish color of the adjoining
liver-cells. (See Fig. 88.) It is more difficult to see this in
sections which cut the capillaries in their longitudinal diam-
eters, but where two or more capil-
laries unite this halo is again seen.
That this appearance is due to the pres-
ence of a true wall seems clear, but all
doubts will be dispelled by watching
the diffusion which takes place in such
a section on the addition of a few drops
of water under the cover glass. The
indigo-carmine becomes dissolved in
the water, forming a deep blue liquid
which stains the surrounding cells and
vessels of a uniform color. While
watching a bile-capillary during the
progress of this action it appears to

stand out more prominently than before, and its walls become
more distinct. In a few moments the cells will have become
swollen by the imbibition of water, and the picture gradually




FIG. 88. Liver of the dog. Nat-
ural injection of bile - capillaries,
showing double contour of the capil-
laries, which are only partly filled
with injection. Cross sections of
the capillaries show a dot of indigo-
carmine surrounded by a distinct
halo. The woodcut does not show
this satisfactorily. In the specimen
the lines corresponding to the walls
of the capillaries are of the utmost
delicacy. Magnified 450 diam.



THE LIVER AND BILIARY APPARATUS. 197

fades, until at length it would be difficult to even locate the
original seat of the capillary. I have verified this over and
over again. The capillary walls seem to be structureless ; at
least with a power of 1,400 diameters I have been unable to
detect any structure. The membrana propria of the inter-
lobular bile-ducts is continued on to the capillaries within the
lobule.

Hering, Henle, and others do not believe that the bile-capillaries possess
walls of their own, but suppose them to be contained within the boundary-
surface of the liver-cells, the latter taking the place of the epithelium of the
interlobular bile-ducts. Henle further quotes Schweigger-Seidel (in the Archiv
far path. AnaL und Phys., XXVII., 505, 1863), who injected the bile-capillaries
with faintly colored gelatine, and showed that by warming the slide the gela-
tine dissolved without leaving any residue whatever. From what has been
said of artificial injections, and recognizing the extreme delicacy of the bile-cap-
illaries, it is not surprising that this result was obtained after injecting a warm
solution of gelatine into the capillaries. The walls of these capillaries are
homogeneous and exceedingly delicate, so that they are destroyed by a mod-
erate degree of heat. Very soon after death they undergo a sort of liquefac-
tion, and what was before a vessel with true walls is now an open channel,
through which an artificial fluid can be made to force its way.

At first the elimination of the indigo-carmine takes place
in the bile- capillaries on the external border of the lobule,
and somewhat later the capillaries about the central vein be-
come filled. Neither the protoplasm of the liver-cells nor their
nuclei ever become stained with the blue solution during the
process of elimination ; such coloring would be the result of
post-mortem diffusion. But the cylindrical epithelium of the
glands is colored blue, and indubitably these glands excrete
the indigo-carmine, as do the cells of the convoluted tubules of
the kidney. Whether they secrete any substance during life,
or what that substance may be, has not yet been determined.

Theile, Kolliker, and Kiernan suppose that these glands secrete a mucous
substance which becomes mixed with the bile. Henle regards these glands
and excavations as reservoirs which are occasionally filled with bile. From
what has been said above it would appear that the cylindrical epithelium of
the glands eliminates the indigo-carmine, and hence we may suppose that
they secrete some fluid or substance during life.

The gall-bladder. The walls of the gall-bladder are about



198 MANUAL OF HISTOLOGY.

2 mm. thick, and are composed of three coats : ' an internal,
mucous and muscular ; a middle, of connective tissue ; and
an external, the serous. The internal coat, 0.4 to 0.5 mm.
thick, is composed of alternating layers of connective tissue
and smooth muscle fibres, the most internal being a layer of
connective tissue which contains a fine meshed capillary net-
work. The connective tissue is dense and the muscle fibres are
arranged in the form of interlacing bands. The internal sur-
face is lined by a layer of cylindrical cells bearing a thickened,
striated edge, and the surface is traversed by a network of
small intersecting ridges, forming, as it were, a sort of lattice-
work. The middle coat, 0.5 to 1 mm. thick, is formed of con-
nective tissue, the meshes of which are wider on the internal
than at the external surface. This coat contains the larger
vessels and nerves. The external, or serous coat is thin, and
consists of a layer of dense connective tissue and peritoneum.
A few mucous glands 2 are found scattered here and there in
the walls of the gall-bladder. Sections from this organ, hard-
ened in alcohol, may be stained with the carmine or picro-car-
mine solution and mounted in glycerine or balsam.

The cystic and common ducts resemble in structure the
hepatic duct. The inner surface of the former is thrown into
crescentic ridges, and in the region of the neck of the gall-
bladder the connective tissue of the internal coat shows a
circular arrangement. The ducts contain no muscle fibres.

The lymph-vessels. These may be divided into a series
of superficial and deep channels. The former are situated in
the capsule of the .liver and form a capillary reticulum with
small meshes, the larger branches of which accompany the
arteries in pairs and communicate with each other by trans-
verse anastomoses. They are found in Glisson's capsule, and
they also form a network somewhat larger meshed than the
preceding. They accompany the hepatic artery and portal
vein and their branches into the interior of the liver, and form
anastomoses with the superficial lymph- vessels. The lymph-
canals may easily be injected with colored material (carmine-
glycerine) by filling a large hypodermic syringe with the liquid
and injecting one of the larger lymph-vessels in the hilus of



1 Henle : Eingeweidelehre.

2 Luschka: Virchow's Archiv, 1857, and Zeitschr. f. rat. Med., 1858.



BIBLIOGRAPHY. 199

the liver. The syringe may be refilled three or four times
without removing the canula, and the injection must be made
in the direction of the normal lymph-current. In this way
the colored liquid will flow backward into the smaller vessels.
During the injection of the larger branches their proximal ends
should be secured by clamps or ligatures.

The nerves of the liver enter the organ at the hilus and fol-
low the course of the vessels. They are composed mostly of
non-medullated elements, a few medullated fibres being found
in the larger branches. They cannot be traced into the lobules.



BIBLIOGRAPHY.

KIERNAN. Anat. and Phys. of the Liver. Philos. Trans. 1833.

LAMBRON. Archiv. gen. 1841.

KRUKENBERG. Mailer's Archiv. 1843.

WEBER, E. H. Muller's Archiv. 1843. Program, col. fasc., II. Lips., 1851.

THEILE. Wagner's Handworterb. Bd. II. 1844.

RETZIUS. Miiller's Archiv. 1849.

WEDL. Sitzungsber. d. Wiener Akad. 1850.

RAINEY. Quart. Jour. Microsc. So. Vol. 1. 1853.

GERLACH. Gewebelehre. 1854.

BEALE. Philos. Trans. 1855. Anat. of the Liver. 1856. Archives of Med. Vols.

I. and II.

VIRCHOW. Virchow's Archiv. Bd. XI. 1857.
LUSCHKA. Henle u. Pfeuffer's Zeitsch. Bd. IV. 1858.
BUDGE. Reichert u. Du Bois-Reymond's Archiv. 1859.
His. Zeitschft. f. wiss. Zoologie. Bd. X. 1860.
WAGNER, E. Archiv d. Heilkunde. 1860. Oester. Zeitschrft f. prak. Heilkunde,

1861.
EBERTH. Zeitschrft. f. wiss. Zoologie. 1860. Med. Centralbl. 1866. Virchow's

Archiv. 1867. Schultze's Archiv f. mik. Anat. Bd. III.
ANDREJEVIC. Sitzungsber. d. Wiener Akad. 1861.
RIESS. Reichert u. Du Bois-Reymond's Archiv. 1863.
SCHWEIGGER-SEIDEL. Reichert u. Du Bois-Reymond's Archiv. 1863.
MACGILLAVRY. Sitzungsber. der Wiener Akad. 1864.
IRMINGER. Zeitschft. f. wiss. Zoologie. Bd. XVI. 1866.
CIIRONSZEWSKI. Virchow's Archiv. Bd. XXXV. 1866.
HERING. Sitzungsber. d. Wiener Akad. 1866. Strieker's Handbuch. Bd. I.

1871.

KOLLIKER. Handbuch d. Gewebelehre. 1867.
VON BIESIADECKI. Sitzungsber. d. Wiener Akad. 1867.
HETDENHAIN. Studien aus d. phys. Instituts z. Breslau. Heft IV. 1868.
KISSELEW. Med. Centralbl. 1869.



200 MANUAL OF HISTOLOGY.