THE ABDOMEN 809 



The fibro-muscular coat is composed of fibrous and plain muscular 

 tissues. The fibrous bands are disposed in all directions, and inter- 

 lace freely with one another. The muscular fibres, which inter- 

 mingle with the fibrous bands, are arranged both longitudinally and 

 transversely. 



The mucous coat is covered by colmnnar epithelium. Its surface 

 presents a great number of small ridges, which interlace in all direc- 

 tions and enclose polygonal depressions or alveoli of various sizes. 

 This pitted appearance bears a resemblance to honeycomb, and 

 the mucous membrane of the vesiculas seminales in the male 

 is similarly arranged. The mucous coat is richly provided with 

 mucous glands. In the neck of the gall-bladder, which describes 

 two curves like the letter 3» there are two fibro-mucous folds, 

 which project into the interior, one opposite each curve, and serve 

 as valves. 



Structure of the Cystic Duct. — ^The wall of the duct is composed 

 of a fibro-elastic and muscular coat, and a mucoiis coat. The former 

 resembles that of the gall-bladder. The mucous coat, which is 

 covered by columnar epithelixun, presents several crescentic folds, 

 disposed obliquely round the wall in a spiral or somewhat cork- 

 screw manner, and succeeding each other at frequent intervals. 

 When the duct is distended, its exterior presents a series of spiral 

 constrictions with intervening swellings. The spiral folds in the 

 interior serve as valves, which are known as the valves of Hetster, 

 or of Amussat. 



Blood-supply. — ^The gall-bladder is supplied by the cystic artery, 

 which is a branch of the right di\nsion of the hepatic. Its course 

 is forwards between the hepatic and cystic ducts to the neck of the 

 organ, where it divides into two branches, superior and inferior. 

 The superior branch ramifies on the upper surface of the organ, 

 between it and the cystic fossa of the liver, whilst the inferior 

 branch is distributed over the inferior surface beneath the peri- 

 toneiuTi. The cystic vein, which is formed by the vmion of superior 

 and inferior branches, usually opens into the right division of the 

 vena portae. 



Lymphatics. — ^These pass between the two layers of the gastro- 

 hepatic omentum to the hepatic glands. 



Nerves. — These are derived from the hepatic sympathetic plexus. 



Development of the Gall-bladder and Cystic Duct. — These are formed in the 

 course of the second month as a diverticulum from the common bile-duct. 



Structure of the Pancreas. 



The pancreas belongs to the class of compound racemose or acino- 

 tubular glands, and bears a close resemblance to a serous or true 

 salivary gland, e.g., the parotid. It has a greyish-pink colour, and 

 is somewhat soft in consistence. It is from 6 to 8 inches long, 

 from I to 1 1 inches deep, except at the right and left extremities, 

 and from i to | inch thick. Its weight is about 3.^ oimces. It is 



