112 PHYSIOLOGY. 



The Gall-bladder. 



The gall-bladder acts as the natural reservoir for storage of the 

 bile. It is a pear-shaped bag of a musculo-membranous texture, 

 capable of containing rather more ihan a fluidounce, and is situated 

 upon the under side of. the liver in a fissure fashioned for it. It is 

 about four inches long, one inch at its fundus, or base. 



The structure of the gall-bladder consists of three coats: an 

 outer, serous coat ; a middle, fibrous; and an inner, mucous coat. 

 The fibrous coat contains both circular and longitudinal fibers. The 

 inner surface of the bladder is lined with mucous membrane, which 

 is of a yellowish-brown color. 



The hepatic duct, formed by union of two bile-ducts issuing 

 from the liver, is about one and one-half inches long. By its joining 

 the cystic, also about one and one-half inches in length, is formed the 

 common bile-duct, known as the ductus communis clioledoclius. This, 

 the largest of the three, is three inches long, with the diameter of a 

 goose-quill, emptying with the pancreatic duct into the duodenum 

 through a common opening;. The motor nerve of the gallrbladder 

 is the vagus; the nerve which supplies the relaxing muscles of the 

 gall-bladder is the sympathetic. 



'*'' / /' 

 Functions of the Liver, 



The liver, being such an important gland, naturally occupies a 

 very prominent position in the general metabolism of the economy. 

 Its principal functions are: the formation of an internal secretion, 

 glycogen; the formation of urea; and, last, the production of the 

 bile, in which as a vehicle many poisonous products are expelled. 



Bile is a thick, golden-colored liquid of a very bitter taste. Its 

 secretion by the liver represents only one subsidiary function of 

 the many performed by this important gland. It represents waste 

 albuminous matters, together with coloring pigments arid mineral 

 salts dissolved in water. Though primarily excrementitious sub- 

 stance and performing the necessary functions of such, it, however, 

 possesses some powers to aid intestinal digestion, both directly and 

 indirectly. These will be discussed under the head of the "Uses of 

 Bile." The secretion of bile is an intermittent process, for a supply, 

 though scanty, is intermittently passing into the duodenum. The 

 arrival of chyme in the duodenum immediately calls for an increased 

 amount, to be followed by a second increase some hours later. 



Starling holds that the mechanism by which the increased secre- 

 tion of bile is produced at the time when this fluid is required in 



