150 ELEMENTARY BIOLOGY. [CHAP. 



diffused throughout a connective-tissue mesh- 

 work (stroma). 



/?. The tunic; a dense connective-tissue investment 

 for the whole, continuous with the stroma. Look 

 for the cut ends of blood-vessels (cf. perimysium, 

 perineurium, periosteum). 



b. Examine under a high power. 



a. The acini ; each composed of a single layer of 

 large epithelial cells, set around a small ir- 

 regular central cavity. 



fB. The ducts ; packed among a, characterized by 

 the large size and regularity of their central 

 cavities ; in section rounded or oval, each lined 

 by an epithelium of squarish cells. 



Look for portions showing the transition of 

 gland into duct. 



1 8. The liver. 



Preserve some small pieces of fresh liver in alcohol, 

 and prepare sections as directed for the pancreas. 



a. Examine under a low power. 



The gland cells will be found to be arranged in 

 groups, around a ramifying system of clear spaces 

 with granular-looking contents (blood-vessels). 



b. Examine under a high power. 



a. The gland cells ; for the most part squarish or 

 hexagonal, each lodging a large round nucleus 

 with one larger and several smaller nucleoli. 



/3. Look for sections of longitudinal series cells; 

 note their arrangement in parallel rows. 



y. Blood capillaries ; cf. supra. The granular ap- 

 pearance seen under the low power will be found 



