DIRECTIONS FOR LABORATORY WORK 801 



lobular blood supply. Nerve supply of the salivary glands? Note dif- 

 ferences between the resting and active (or stimulated) gland. ~ 



(B) THE PANCREAS. 



(1) Study a stained section of the pancreas. Make l.p. sketch (269) 

 to show the arrangement into lobes and lobules, and the location of the 

 ducts. Sketch h.p. (270) an acinus with its intercalary duct (inter- 

 mediate duct), and a centro-acinal cell group. Note the polar differen- 

 tiation of the zymogenous acinar cells ; and the different staining reaction 

 of the zymogenous and the centro-acinal cells. Significance? What is 

 the relationship between the distal granular zone of the zymogenous cells 

 and their basal filar zone ? the mitochondria ? the 'nebenkern' ? How do 

 these structures vary according to the phase of functional activity? 



(2) Sketch h.p. (271) a pancreatic islet (island of Langerhans). 

 From a specially prepared demonstration slide of the pancreas sketch 

 (272) cells of the A and B types. Number, form, distribution, staining 

 reaction, and significance of the islets? 



(3) Sketch h.p. (273) a cross-section of a large interlobular duct. 

 From an injected specimen of a cat's pancreas sketch (274) the 



blood supply of the zymogenous parenchyma and of the islets. Signifi- 

 cance of the relatively great vascularity of the islet? Eelation of the 

 cap llaries to the cords of islet cells? Enumerate the differential marks 

 between the pancreas and the parotid gland. 



(C) THE LIVER (Hepar). 



(1) Study l.p. a stained section of the liver: a, of pig or camel; b, 

 turtle or frog; c, cat or human. Enumerate differences. From sections 

 a and c sketch l.p. (275) a hepatic lobule including the capsule of Glis- 

 son. From section b, sketch h.p. (276) a small extent of the liver 

 tubule, noting the definite structural polarity of the constituent cells.- 

 Functional significance of the latter phenomenon? Similarity between 

 embryonic mammalian liver and the adult reptilian and amphibian 

 livers ? Significance ? What is the shape of the liver lobules as revealed 

 by reconstructions? Difference between a hepatic lobule and a portal 

 lobule ? 



(2) Study h.p. a stained section of the human or cat's liver. Sketch 

 h.p. (277) a small area, noting the hepatic cell-cords (trabeculse), the 

 interstitial reticulum, the capilliform sinusoids (intralobular capil- 

 laries), the relation of the latter to the cell cords, and of the stellate 

 cells (of von Kupfer) to the endothelial lining cells and to the liver 



