790 DIRECTIONS FOR LABORATORY WORK 



(B) LYMPH VESSELS (lymphatics). 



(1) LYMPH CAPILLARIES. Identify a lymph capillary in a stained 

 section (e.g., lymph node, subcutaneous tissue, submucosa of trachea or 

 large intestine) and sketch (182). How does it differ from a blood 

 capillary? a venule? a sinusoid? 



(2) LACTEAL. Sketch (183) the terminal lymph capillary in a villus 

 of a stained section of the small intestine. 



(3) THORACIC DUCT. Sketch (184) a segment of the wall of a 

 stained section of the thoracic duct (Weigert's elastic tissue stain, and 

 picric-acid-fuchsin). Note the several layers, and the fundamental tis- 

 sues of each. How can you distinguish between a large lymphatic and 

 a vein of the same calibre? Do lymphatics contain valves? 



(C) SEROUS MEMBRANES (Peritoneum, Pleura, and Pericar- 



dium). 



Sketch (185) h.p. a small area of a stained toto mount of a frag- 

 ment of the peritoneum treated with silver nitrate. Note the character 

 of cells and intercellular stomata. Sketch (186) also a short segment 

 of a stained section of same. Note shape and character of cells; inter- 

 cellular bridges, striated border, basement membrane, and the submeso- 

 thelial fibre-elastic corium. 



(D) LYMPH NODULES (Lymph follicles). 



Sketch (187) l.p. a small lymph nodule from the submucosa of a 

 stained section of large intestine, stomach, or vermiform appendix. 



(E) LYMPH NODE (Lymph gland). 



Study a stained section of a mesenteric lymph node. Sketch (188) 

 l.p. Sketch (189) h.p. small area including a medullary cord and the 

 adjacent lymph sinus. What is the predominant cell type ? Note divid- 

 ing cells in germinal center of cortical nodules. Examine in Ringer's 

 solution scrapings from a lymph node of cat, after addition of drop of 

 methylene blue. Examine also a glycerin mount of aceto-carmin pre- 

 served material. 



(F) LYMPHOID ORGANS. 



(1) HEMOLYMPH NODE. (Hemal Node). Study a stained sec- 

 tion of a hemolymph node of sheep. Sketch (190) h.p. a small area 

 including the denser and looser parenchyma. Differential characteris- 



