1058 THE DIGESTIVE SYSTEM. ’ 
shown by the darkly-shaded parts in Fig. 712, the back of the mesenteries of the ascending, 
descending, and iliac portions of the colon, adheres to the posterior abdominal wall, and 
these mesenteries become lost; whilst the mesenteries of the transverse and pelvic portions 
of the colon remain free, and persist in the adult. 
At the same time, the mesentery proper (which was at first attached only at its 
narrow neck, between the duodenum and transverse colon, and below this was continuous 
on the right with the ascending mesocolon), now acquires a new attachment to the 
posterior abdominal wall through the absorption of the ascending mesocolon (Fig. 712), 
and the adult condition is attained. | 
THE LIVER. 
The liver (hepar) is a large glandular mass of irregular shape, which lies 
under cover of the ribs in the upper and right portion of the abdominal cavity, 
immediately beneath the diaphragm (Fig. 714). It is the largest of all the 
digestive glands, and plays an umportant part in the metabolism ‘of both carbo- 
hydrate and nitrogenous materials: in addition, it secretes the bile—a fluid 
which although chiefly excretory, assists to some extent in pancreatic digestion. 
From the liver the bile is conveyed to the duodenum by the bile duct, in con- — 
nexion with which is found a pear-shaped diverticulum, for the temporary storage — 
of the bile, known as the gall-bladder (Fig. 716). | 
Form.—The liver is so irregular, and varies so considerably in size and shape 
in different bodies, and even in the same body under different conditions, that it — 
is difficult to convey a true idea of its form. This, perhaps, may be most readily — 
realised from a consideration of the portion of the abdomen in which the liver — 
lies, and to the shape of which its form is chiefly due. 
The upper portica of the abdominal cavity is dome-shaped, its anterior, posterior, 
and lateral walls, as well as its roof, being formed chiefly by the vaulted under surface 
of the diaphragm, which slopes down on the inner aspect of the ribs as far as the 
lower border of the thoracic framework. In the right and middle portions of the 
dome-shaped space thus formed the liver lies, like a cast in its mould, and from it 
chiefly its form is derived. And, if an imaginary plane be passed backwards and 
upwards, from an oblique line extending across the anterior abdominal wall, from a 
point immediately below the right margin of the ribs to a point one inch below 
the left nipple, it will cut off a segment of the abdominal cavity which corre- 
sponds tolerably accurately to the live er, in both size and form. 
Accordingly, the liver may be described as having two chief surfaces: a parietal 
surface, convex in general outline, which fits into the arch of the diaphragm ; and 
a visceral surface, irregular in form, which looks downwards, backwards, and to the 
left, and rests upon the abdominal viscera. These two surfaces are separated from 
one another by the inferior margin of the liver. 
Symington has described the liver, when hardened in situ, as a right-angled triangular prism 
with its right angles rounded off, and as having five surfaces—-anterior , posterior, superior, right, 
and inferior. The first four of “these would be ine ‘luded in the parie stall surface described above, 
and the inferior corresponds to the visceral surface. Symington’s description has received a 
very W ide ae ceptance. 
Previously His had described three surfaces : an inferior , corresponding to the visceral, and a 
superior and posterior, which together correspond to the parietal surface. 
Before His’s description, which changed all previous views on the form of the liver, 
became current, 1t was described as having two surfaces, an upper and a lower, and two 
borders, an anterior thin and a posterior ‘thick ; and this is the shape of the ordinary soft 
(lissecting -room liver, which flattens out into a cake-lke form when removed from the 
body. 
In the body, on the other hand, instead of being flattened out in this way, it is folded, as it 
were, around its portal and longitudinal fissures ee a much more compact mass ; and if tharde 
ened in situ before its removal, it presents an appearance very different trom that of the soft liver 
just referred to. From astudy of such hardened specimens it will be seen that the mass of the right 
lobe hes chiefly in an antero- posterior direction, its posterior thick portion fitting into a wide groove 
at the side of the vertebral column, and its long axis running from behind forw ards and a little 
inwards. The left lobe, leading off from the anterior part of the right lobe, is folded across the 
front of the vertebral column and great vessels, its long axis running transv ersely, but 1t does 
not usually pass back at the side of “the vertebral column, like the right lobe, into the vertebral 
groove ; so that there is no real notch, as usually described, at the back of the liver for the 
