786 DIRECTIONS FOB LABORATORY WORK 



(d) In a toto mount of mesentery, treated with silver nitrate, sketch 

 (155) the endothelial lining of one of the smaller vessels. 



(e) Sketch (156) in longitudinal or oblique section a capillary, and 

 a precapillary vein in the bone marrow of a developing membrane bone, 

 e.g., jaw of pig fetus of 35 mm. 



(At this stage the student should review his slides, noting in each 

 section: (a) the type of epithelium present; (b) the type of connective 

 tissue; (c) muscle; (d) nerves; and (e) types of blood vessel. Several 

 laboratory periods may be spent to advantage on this exercise.) 



(D) HEART (Cor). 



(1) Make gross study of heart (human, hog, dog or beef) and note 

 in intact organ: (a) ventricles, (b) atria, (c) auricular appendages, 



(d) pericardium (visceral and parietal portions), and (e) the roots of 

 the several large arteries and veins (aorta, pulmonary artery, inferior 

 and superior vena cava,*and the pulmonary veins). Open the several 

 chambers and note in the ventricles : (a) columns carnese, (b) papillary 

 muscles, (c) chordae tendinese, attached to the valves guarding the atrio- 

 ventricular orifices, (d) the moderator band of the right ventricle, and 



(e) the semilunar valves guarding the aortic and pulmonary orifices. In 

 the atria note the (a) pectinate muscles of the auricular appendages and 

 (b) the crista terminalis. Note also the inter atrial and the interven- 

 tricular septa, and expose the atrio-ventricular bundle (bundle of His) 

 in the anterior septal portion of the heart. 



(2) Study a stained transverse section of the heart of a mouse (or 

 other small mammal) cut through the ventricles. Note (a) epicardium, 

 (b) myocardium, (c) endocardium, (d) papillary muscles, (e) columns 

 carnese. Sketch under l.p. (157). 



(3) Study a stained section through the ventricular wall of the 

 human heart. Note the several layers, and compare with the three 

 tunics of a large blood vessel. Make l.p. sketch (158). 



(4) From stained sections make h.p. sketches of (a) epicardium 

 (159), (b) endocardium (160), (c) Purkinje fibers, in transverse sec- 

 tion (most conspicuous in rabbits and sheep's heart) (161), and a cusp 

 of an atrio-ventricular valve, including base (annulus fibrosus) and 

 apex, noting in each case the component tissue elements (162). 



(5) Make drawings from demonstration preparation of the node of 

 the sino-ventricular bundle, showing the constituent muscular and con- 

 nective tissue elements (163), and the nerve and blood supply (164). 

 Structure of sino-ventricular bundle of His? of the moderator band? 



