THE VISCERA. 219 



2. A fibrous (muscular) coat, consisting of an internal stronger layer of 

 longitudinal fibres, and an external of circular, similar to that of the vessels, 

 is united with the serous by areolar tissue, is little extensible, and connected 

 with the muscular coat of the intestinal canal. 



3. Mucous membrane, villous, with short irregularly crossing folds (like a 

 net), beset with villi. greyish white, coloured yellow by the bile, presents at 

 the neck ("where externally we remark the screw-like appearance) two small 

 valves, but which assist neither the entrance nor the exit of the bile. (The 

 space between the two is sometimes expanded like a sac, where gall-stones 

 then form.) The internal surface is covered with cylindrical Epithelium. 



Vessels: Art. cystica from ram. 'dext. art. hepaticce. Ven. cystica passes into 

 the right branch of Ven. porta. Lymphatics: very numerous, sometimes 

 coloured yellow, pass into plex. portarum and gland, coeliacae. Nerves: from 

 plexus hepaticus. 



Function: The gall bladder preserves the bile brought to it through ductus 

 hepaticus and cysticus for a time, and is again emptied through ductus cysticus 

 and choledochus. 



Bile (see 10). 



448. c. The duct of the gall-bladder, ductus cysticus, 



the continuation of the neck of the gall bladder, from which it 

 passes downwards and to the left, is thinner and shorter than the 

 hepatic duct, passes downwards upon the right side of ductus 

 hepaticus, and unites with this at a very acute angle in the d. 

 choledochus. Situation: in the lig. hepatico-duodenale, before 

 ven. cava inferior, to the right of art. cystica. 



449. d. The common bile duct, ductus communis choledochus, 



formed by the united ductus cysticus and hepaticus, passes in 

 the same direction as the last, obliquely downwards, rather back- 

 wards and to the right, has a thickness equal to a moderate goose- 

 quill, and a length of from two to two inches and a half. At the 

 superior part it lies in the lig. hepatico-duodenale, before ven. 

 portx, below art. hepatica, along the right side of art. gastro- 

 epiploica dextra, surrounded by uniting tissue and lymphatic 

 glands ; then behind and on the internal border of the pars descend, 

 duodeni in a groove on the head of the Pancreas; lastly, it per- 

 forates very obliquely the muscular coat of pars descend, duodeni 

 at its centre, passes six or seven lines between the muscular and 

 mucous coat, on the right side of duct, pancreaticus, perforates 

 the mucous membrane on the internal wall of the inferior portion 

 of the pars desc. duodeni with a round opening (so that a retro- 

 grade course of the bile, &c., is impossible), after having received, 

 shortly before, the duct, pancreatic. 



Structure. It is like the duct of the gall bladder. 



