M 8 ELEMENTS OF MAMMALIAN ANATOMY. 



and lungs from an injected cat, and carefully dissect away 

 the fatty and connective tissues enveloping the vessels. 



The peripheral connection between the arteries and veins 

 is by means of capillaries, which are microscopic vessels 

 with an extremely thin wall composed of a single layer of 

 epithelial cells. These capillaries are so abundant every- 

 where in the flesh that a needle cannot be inserted without 

 penetrating some. They form a kind of mesh or network, 

 so that every cell may be supplied with oxygen and food 

 and discharge its waste matter. All the blood carried to 

 any portion of the body by the arteries is not returned by 

 the veins, as a considerable amount of the plasma and some 

 of the white corpuscles escape through the thin capillary 

 walls and are returned to the circulation by a system of 

 vessels called lymphatics (Fig. 80). 



PRACTICAL QUESTIONS AND SUGGESTIONS. 



1. What holds the heart in place? 



2. Draw the ventral aspect of the heart with the pericardium re- 

 moved and label all features. 



3. When the heart is detached from the body, how do you distin- 

 guish the dorsal from the ventral aspect? 



4. How many veins open into each auricle? 



5. What arteries lead from each ventricle? 



6. After dissecting write a detailed description of the valves of the 

 heart. 



7. Describe the differences in the appearance of the walls of the 

 aorta and vena cava. 



8. From your dissection write a description of the features seen in 

 each cavity of the heart. 



9. Name the branches of the thoracic aorta in order. 



10. Name the branches of the abdominal aorta and tell what organs 

 each supplies. 



11. Draw the cceliac axis and its branches throughout their course 

 and label all parts. 



12. Show by a drawing the relations of the aorta and venae cavse 

 throughout. 



13. Make a diagrammatic cross-section of the neck, showing location 

 of arteries and veins. 



