LECTURE VIII. 

 CIRCULATION. 



Blood is a complex fluid consisting of serum, hbnn factors, 

 and for present purposes two kinds of corpuscles, — the red and 

 the white. Its temperature differs in the various domestic ani- 

 mals from loi to 104 degrees F, The horse 100 to 101.5 degrees 

 F. and the cow about one degree higher; sheep vary from 100 

 to 104 degrees. Its specific gravity is about 1050 and it consti- 

 tutes about one-tenth the body weight. 



Circulatory apparatus. -Heart, arteries, veins, capillaries, lym- 

 phatic vessels and lymph glands. 



The heart is located within the pericardium, which supports 

 the heart in place beneath the 3rd, 4th, and 5th dorsal vertebrae 

 by attaching to the large blood vessels at its base; to the dia- 

 phragm behind, and to the sternum below. It measures about 

 10.5 inches in length by 7.5 wide at the base; cone shaped; and 

 weighs 6.75 pounds. The heart contains four cavities, easily seen 

 by cutting the heart open. Two located at the base are called 

 auricles ; and two at the apex, ventricles. 



TTie auricles are much aHke, as are also the ventricles, ex- 

 cept that the left ventricle is larger and has a wall which is 

 more than twice as thick as the right. The heart is covered by 

 the pericardium and lined with the endocardium. Its muscle 

 fibers are involuntary so far as control is concerned, but are 

 striped. 



Course of the blood. — Beginning with the blood entering the 

 right auricle through the anterior and posterior vena cavae and 

 coronary veins it then passes through the right auricle thence 

 into the right ventricle, thence to the lungs through the pulmo- 

 nary artery, back to the left auricle through four pulmonary 

 veins, past the valves on the left side, to the left ventricle and 

 is then sent by this ventricle through the systemic circuit. The 

 systemic blond leaves the loft ventricle through a large artery 

 called the aorta. 



