AND PHYSIOLOGY. 165 



brane, in order to increase the amount of its secretory surface. 

 It is the presence of villi that gives to some parts of the mu- 

 cous membrane a velvet-like appearance, and in these villi 

 are found the commencement of the lacteals, one lacteal 

 usually being found in each villus. 



303. Glands attached to t lie Intestines. — Connected 

 with the Alimentary Canal are several large glands, a few of 

 which have already been described. They are soft solids, of 

 various forms and sizes, and are composed of lobules or small 

 divisions, each one of which is supplied with an artery, vein, 

 and duct. Each of these ducts communicates with the prin- 

 cipal duct or outlet, which convey3 away the product sepa- 

 rated from the blood by the whole gland. In microscopic 

 structure, a gland is made up of very minute cells, which 

 seem to have the power of secreting or separating from the 

 blood the particular substance which it is the function of the 

 gland to eliminate. 



304. The Liver, Gall-Bladder. — First in importance of 

 this class is the Liver. (Fig. 178, p. 166.) This, except- 

 ing the brain, is the largest organ in the body, and is situated 

 on the right side of the abdomen, corresponding to the stom- 

 ach on the left, and is of a reddish yellow color. The average 

 weight of it is four pounds, measuring twelve inches in its 

 longest diameter, and it is divided into five lobes or great divis- 

 ions, and these are entirely composed of minute bodies or 

 lobules, (Fig. 179, p. 166), which are about the size of millet 

 seeds, each one containing an artery, a vein, and a plexus, or 

 net- work of ducts for conveying away the bile. These differ- 

 ent plexuses unite with each other and form two hepatic ducts 

 which discharge the bile into the Gall Cyst or bladder. (Fig. 

 180, p. 167.) This is a pear-shaped sac, containing from 

 one to two ounces, of a greenish yellow color, situated under 



Describe the Villi. 303. What is sai l of the large glands connected with the organs of 

 digestion? State the structure of a gland. 304. What is the relative size of the Liver? 

 Where is it located? State its color and weight. Give its minute structure. What is 

 the Gall Cyst or Bladder? What is the duct that carries the Bile to the Gall Cyst, and 

 the one that empties the Gall Cyst into the Duodenum ? 



