976 THE ORGAXS OF DIGESTION 



series of arches from the cfficuni. where the vasa intestini tenuis anastomose with 

 the ileo-colica, the first branch of the superior mesenteric given to the large 

 intestine. 



The blood-supply of the rectum is from the inferior mesenteric by the superior 

 ha^morrhoidal, from" tlie internal iliac by the middle ha^morrhoidal, and from the 

 internal pudic by the inferior luemorrhoidal. The vessels at the lower end of the 

 rectum assume a longitudinal direction, connnunieating freely near the anus, and 

 less freely above. 



The blood of the large intestine is turned into the portal vein by means of the 

 superior mesenteric and inferior mesenteric veins. At the rectum a communication 

 is set up between the systemic and portal system of veins, since some of the l)lood 

 of that part of the intestine is returned into the internal iliac veins. In the lower 

 end of the rectum the veins, like the arteries, are arranged longitudinally. This 

 arrangement is called the luvmorrhoidal plexus. 



The nerves and lymphatics of the large intestine differ in no important 

 particular from those of the small intestine. 



TRE LIVER 



The liver — the largest gland in the body — is situated in the upper and right 

 part of the abdominal cavity f figs. 565, 578). It is of most irregular shape. It 

 weighs between forty-five and sixty ounces. In females the liver is smaller than 

 in males. It bears a different relation to the body weight at different ages. It 

 forms one-fortieth part of the weight of the body in the adult male, and one- 

 thirty-sixth in the adult female. In the foetus, at the fourth month, it is one-tenth 

 the weight of the body, and in the infant at birth one-twentieth (fig. 578). It 

 measures from right to left seven to ten inches, from before backwards three to 

 six inches, and six to seven inches from above downwards in the thickest part of 

 the right lobe. It is of a chocolate or reddish-brown color, is solid and firm to the 

 touch, but frial)le. Its bulk is equal to ninety-five cubic inches. 



In the description which follows it will be noted that there are two borders — 

 anterior and posterior; two extremities — right and left; three surfaces — superior, 

 inferior, and posterior; five lobes — right, left, quadrate, caudate, and Spigelian; 

 five fissures — umbilical, fissure for the ductus venosus, transverse, fissure of the 

 vena cava, fissure for the gall bladder; five ligaments — coronary, suspensory or 

 falciform, round, right and left lateral. 



The liver is seen to be divided by means of a fold of peritoneum — the suspen- 

 sory ligament — into two very distinct parts, the right and left lobes (figs. 578, 579). 



The anterior border of the liver is well defined, appearing as a sharp thin edge. 

 To tlie left of the middle point at the beginning of the longitudinal fissure is the 

 interlobar notch, marking the division between the right and left lo1)es. Further 

 to the right is a notih for the gall bladder. 



The posterior border is thick, rounded, and fixed, is slightly marked by the 

 spinal colunni, and notched for the vena cava. 



The right extremity is tliick, and rounded like the posterior border. The left 

 extremity is thin and fiat like the anterior border. 



The surfaces are described as thoy are seen in a liver which has been hardened 

 III fi'itii. 



The superior surface of the liver is convex, and moulded to the surface of the 

 diaphragm. It is smooth, and covered by peritoneum. It is divided by the sus- 

 pensory ligament, which runs from ])efore backwards, into two parts: the right and 

 left lol)es, the right division l)eing much the larger (fig. 579). Upon this surface of 

 the left lobe is a shallow de})ression for the heart. The surface of the left lobe is 

 much less convex than that of the right. A considerable portion of this surface 

 faces anteriorly, and some writers divide it into anterior and upper surfaces. 



