Varieties of position are more frequent than those of diversity of form. During utero-gesta tion the liver is usually pressed considerably above its ordinary plane, so as to impede more or less the action of the diaphragm and pro duce embarrassed respiration. In an extremely fat subject I once saw the diaphragm raised by the liver to a level with the fourth intercostal space, measured near to the sternum. In its natural position the thin margin of the liver scarcely reaches the border of the thorax, but in women who have laced tightly during youth nothing is more common than to find this edge forced several inches below the base of the thorax, and altered in its form. In these cases the direction of the aspects of the organ are likewise changed; the convex surface looks di rectly forwards, instead of upwards and for wards, and lies in contact with the abdomina. parietes. The concave surface is directed back wards in place of downwards and backwards, and time posterior border is forced upwards. In a sketch from the subject, now before me, the greater part of the convex surface of the organ is in contact with the abdominal pa rietes, and the free margin extends into the umbilical and lumbar regions. In another sketch, as a result of the enormous magnitude of the stomach from the same cause, the liver is raised almost perpendicularly, the extremity of the left lobe being in contact with the dia phragm, and the right lobe in the right iliac fossa. A part of the liver has been found in the sac* of inguinal and umbilical hernia. Various peculiar appearances are observed in the liver of the foetus arising from arrest of development. Thus, for instance, the entire organ, or a part of it, may be situated in the chest, or from absence of development of the abdominal parietes the liver may form part of an exabdominal tumour, and be uncovered ex cepting by the membranes of the ovum. But the most interesting and unexplained form of altered position is that in which the whole of the viscera of the body are transposed, and the liver becomes placed on the left instead of the right side. These cases are generally perfect, and the peculiarity does not seem to interfere with the life or functions of the subject. The liver presents its natural form and size, and with the simple exception of left for right, pre cisely the same relations. The aorta, of course, occupies the right side, and the vent: cave the left, while the stomach is transferred to the right. Sir Astley Cooper has preserved the viscera of an adult who was the subject of this transposition. And a few years since I had the opportunity of examining a similar case in the body of Smithers, a man who was executed for committing arson accom panied with loss of life in Oxford-street. The viscera of this man were perfectly healthy, the liver finely formed, and the general fabric ro bust.
The gall-bladder (fig. 33, 12,) (cystis fellea) is a membranous sac of a pyriform shape, situated in the shallow fossa upon the under surface of the right lobe, and lying pa rallel with the longitudinal fissure. For con venience of description it has been customary to divide it into a body, fundus, and neck (cervix), although no precise mark of division subsists between these parts. The body is the middle portion ; the fundus the expanded ex tremity, which approaches the notch in the free border of the liver, and frequently extends be yond it ; and the neck the narrow and taper ing portion of the sac which enters the right extremity of the transverse fissure and forms the cystic duct.
The sac is in relation by its upper surface with the substance of the liver, and by the under part with the pylorus and ascending duodenum. The fundus corresponds with the right border of the rectus muscle, and may be felt in that situation when filled with gall stones.
The coats of the gall-hladder are three :-1.
an external or serous covering derived from the peritoneum, which covers all that portion of the sac which is not in contact with the sub stance of the liver. The gall-bladder is some times completely surrounded by the peritoneum, and hangs loosely connected with the liver by a duplicature of that membrane. 2. A fibrous layers (nervous) composed of cellulo-librous tissue intermingled with tendinous fibres; and, 3. a mucous coat which lines the interior of the sac, and is continuous through the cystic and hepatic ducts with the mucous lining of the biliary structure of the liver, and through the ductus communis choledochus with the mu cous membrane of the duodenum and ali mentary canal. The internal surface of the mucous layer is raised into innumerable small ridges and folds (rugas) by the ramifications of the cystic artery and its capillaries, which give to it a peculiarly reticulated appearance, and the iuterspaces of the rugs: are depressed into numerous small muciparous follicles. In the neck of the sac the mucous membrane is pro duced into from six to twelve small folds, forming a kind of spiral valve by means of which the bile is regulated in its descent into the duodenum, and assisted in its entrance into the gall-bladder. The existence of this pecu liar valvular apparatus gives to the neck of the gall-bladder a sacculated appearance. The mu cous membrane is but loosely connected with the fibrous coat, and the cystic artery with its branches ramify between them.
The excretory duct of the gall-bladder is the cystic, (fig. 33, 11) ; it is about an inch and a half in length, and in diameter about equal to the cylinder of a crow's quill. It is generally somewhat tortuous in its course, and appears sacculated from the continuation into it of the spiral valve. Upon entering the transverse fissure it unites with the excretory duct of the liver, the hepatic duct, and die junction of the two constitutes the ductus communis choledochus. The ductus comma? os choledochus, about three inches in length, des cends through the right border of the lesser omentum, lying in front of the portal vein, and to the right of the hepatic artery, and opens into the duodenum by passing for some dis tance obliquely between its coats. It is united to the other vessels in its course by the cellular tissue of Glisson's capsule, and near to its ter mination is considerably constricted.
The excretory ducts of the liver and gall bladder have three coats, an external or cellular coat, a middle or fibrous, and an internal mu cous. A question exists among physiologists as to the probable muscularity of the middle coat in man; it is undoubtedly contractile, and in some few instances of obstruction has pre sented an appearance very closely resembling muscular fibres. Cruveilhier thinks the struc ture analogous to the dartos. In some animals, as in the horse and dog, this coat is clearly muscular.
Varieties in the gall-bladder.—The sac is sometimes enormously dilated without any ap parent obstruction in its ducts. Occasionally in acephalous and anencephalous fcetuses it is altogether absent. In a preparation now before me of the liver of a foetus at the full period, which lived for several hours after birth, and which presented, in anatomical structure, several peculiarities dependent upon arrestof de velopment, the most careful dissection has failed to discover the slightest indication of gall-bladder. Among the lower mammalia, as in cats, a double or accessory gall-bladder is by no means uncommon. Kiernan has ob served several instances of this variety. I my self have seen two, and have one at present before me. In the kinkaju an accessory gall bladder is the normal character, and in the liver of a small animal preserved by Hunter in the Museum of the College of Surgeons, there are three gall-bladders.