46 



85. Aorta. Homo. Transection or longLsection of the aorta. 

 Assigned for study. Picric alcohol ; paraffin ; stained with 

 hematoxylin and picrofuchsin. 



Study carefully in comparison with 83 and 84. Are internal or 

 external elastic membranes present ? What is the relative thickness 

 of the coats and the relative amounts of muscle and elastic tissue in 

 the media ? Are vasa vasorum to be seen in the adventitia ? 



VEINS. 



86. Femoral vein (and artery). Transection of the 

 femoral artery and vein. ; paraffin ; sections yu . 

 Stain with hematoxylin minutes, picrofuchsin seconds. 



Identify the artery from your knowledge of its structure as 

 gained from a study of 83, and compare with it the vein, observing 

 the differences and resemblances in the following particulars : (a) 

 the thickness of the wall, (6) its flaccidity, (c) the presence of blood 

 in the lumen, (^) relative thickness of the coats, (^) relative 

 amounts of white connective tissue, elastic tissue and muscle pres- 

 ent. From a study of their structure, compare arteries and veins as 

 to their elasticity and contractility. 



CAPILLARIES. 



87. Vascular epithelium. Demonstration of the 

 vascular epithelium as seen in capillaries and arterioles. Silvered 



(§ 146). 



Note the shape of the cells as outlined by the blackened cell- 

 cement ; their relative size in the capillaries. Remember that the 

 vascular epithelium is the structure common to all parts of the vas- 

 cular system. 



88. Capillaries in striated muscle. Demonstration. Free- 

 hand longitudinal section of muscle that was injected with carmine 

 gelatin mass (§ 127). 



Study carefully the capillary network and its relation to the 

 muscle fibers. 



89. Capillaries of plain muscle. Rabbit. Demonstration. 

 The blood vessels of the small intestine were injected with carmine 

 gelatin mass (§ 127), the muscular coats stripped off, pieces of the 

 longitudinal coat laid out flat. Balsam mount. 



