THE VASCULAR SYSTEM. 149 
14. Describe the three routes by which blood may reach the brain 
and the two routes by which it may be returned to the heart. 
15. Name the arteries arising from the arch of the aorta. 
16. Draw the inner or medial aspect of your dissection of the arteries 
of the thoracic limb and label all parts. 
17. Draw cross-section of arm at middle of humerus to show location 
of main artery and vein. 
18. Draw cross-section of the middle region of the forearm to show 
location of chief arteries. 
9. Draw outline of the bones of the manus and show relation of 
arteries to bones as seen from palmar aspect. 
20. Draw outline of femur and show course of main artery in relation 
to the bone as seen from medial aspect. 
21. Draw outline of bones of the pes and show relations of the 
arteries to the bones as seen from the plantar aspect. 
22. At what points in its course is the chief artery of the pelvic limb 
most superficial ? 
23. Describe the difference in structure of a vein and an artery. 
24. What veins open into each auricle of the heart? 
25. Name the veins returning the blood from each organ of the 
abdominal cavity. 
26. Draw the portal system and label all vessels. 
27. Describe the veins returning the blood from the head. 
28. Describe the chief blood sinuses in the skull. 
29. Where are the valves found in the blood-vessels? 
30. If the brachial vein were cut, how could the blood from the 
manus reach the heart? 
THE LYMPHATIC SYSTEM. 
The lymphatics constitute that part of the vascular sys- 
tem which collects the colorless fluid called lymph from 
the tissues, and the chyle from the small intestine, and con- 
veys them to the external jugular veins. The portion of the 
lymphatic system originating in the villi of the small in- 
testine and conveying the chyle to the left thoracic duct is 
known as the Jacteals (Fig. 65, 6). 
The lymphatic system consists of four parts: (1) the 
lymphatic spaces between the skin and muscles in all 
parts of the body, the spaces between the muscles adjacent 
to the bones, and internal spaces such as those enclosed by 
