154 THE ESSENTIALS OF HISTOLOGY 



LESSON XXXI. 



STRUCTURE OF THE LIVER AND PANCREAS. 



1. MAKE sections of liver and study them carefully with a low and high 

 power. Sketch the general arrangement of the cells in a lobule under the 

 low power and under the high power. Make very careful drawings of some 

 of the hepatic cells and also of a portal canal. 



2. Study, first of all with the low and afterwards with a high power, a 

 section of the liver in which both the blood-vessels and the bile-ducts have been 

 injected. Make a general sketch of a lobule under the low power and draw a 

 small part of the network of bile-canaliculi under the high power. 



3. Tease a piece of fresh liver in salt solution for the study of the appear- 

 ance of the hepatic cells in the recent living condition. 



4. Prepare sections of the pancreas from a gland which has been hardened 

 in alcohol. The sections are stained with borax- carmine and mounted in 

 the usual way in Canada balsam. 



Make a sketch under the low power. 



5. Tease a small piece of fresh pancreas in salt solution. Notice the 

 granules in the alveolar cells, chiefly accumulated in the half of the cell which 

 is nearest the lumen of the alveolus, leaving the outer zone of the cell clear. 



Sketch a small portion of an alveolus under a high power. 



THE LIVER. 



The liver is a solid glandular mass, made up of the hepatic 

 lobules. These are polyhedral masses (about 1 mm. in diameter) of 

 cells, separated from one another by connective tissue. In some 

 animals, as in the pig, this separation is complete, and each lobule is 

 isolated, but in man it is incomplete. There is also a layer of con- 

 nective tissue underneath the serous covering of the liver, and forming 

 the so-called capsule of the organ. 



The blood-vessels of the liver (portal vein and hepatic artery) enter 

 it on its under surface, where also the bile-duct passes away from the 

 gland. The branches of these three vessels accompany one another 

 in their course through the organ, and are enclosed by loose connec- 

 tive tissue (capsule of Glisson), in which are lymphatic vessels, the 

 whole being termed a portal canal (fig. 187). The smallest branches 

 of the vessels penetrate to the intervals between the hepatic lobules, 

 and are known as the interlobular branches. The blood leaves the 

 liver at the back of the organ by the hepatic veins : the branches of 

 these run through the gland unaccompanied by other vessels (except 



