10 



CHAPTER II. 

 Blood. 



HEART AND BLOOD-VESSELS CIRCULATION OF BLOOD BLOOD — 



COAGULATION OF ELOOD NUTRITION AND WASTE DISTRIBU- 

 TION OF BLOOD IN THE BODY ANiBMIA CONGESTION INFLAM- 

 MATION REPAIR AFTER INFLAMMATION COUNTER-IKRITATION — 



BLEEDING. 



HEAUT AND BLOOD-VESSELS.— The heart (Fig. 3), ivhich is a hollow 

 muscle, is divided by a longitudinal partition intO' two independent pa,rts, 

 namely, the right side and the left side. Each of these is separated into 

 two compartments (an auricle and a ventricle) by a valve, which, under 

 conditions of health, allows fluid to flow from an auricle into the ventricle 

 of its own side ; but does not permit it to go in the opposite direction. 

 The heart is of a more or less conical shape, with the apex pointing down- 

 wards. The auricles, which are much smaller than the ventricles, occupy 

 the base, and the ventricles the remainder of the heart. The left ventricle 

 opens into the aorta, which is the largest of all the arteries, and which, 

 shortly after leaving the heart, splits up into branches that distribute their 

 still smaller ramifications to every part of the body, and finally terminate, 

 as a rule, in capillaries. In Fig. 3, the aorta and its branches, the 

 pulmonary arteries, the veins of general circulation and the pulmonary 

 veins are respectively shown, for convenience' sake, as consisting of a single 

 trunk. The capillaries are found in countless numbers throughout the 

 entire system. These minute tubes have extremely thin walls, are about 

 js^jij of an inch in diameter, and probably do not exceed jV of an inch in 

 length. They open into the veins, which are very small at first ; but 

 gradually uniting with each other, enter the right auricle by two large 

 branches, and a few small ones. The right auricle communicates, as I have 

 already said, by a valve with the right ventricle, which opens into the 

 pulmonary artery. This artery proceeds to the lungs, and becomes split 

 up into branches and finally into capillaries that spread themselves through 

 the air-cells of the lungs. These air-cell capillaries unite to form the 

 pulmonary veins, which open into the left auricle. 



CIRCULATION OF BLOOD.— Each side of the heart acts like one of 

 those india-rubber pumps which, when dilated, becomes filled with fluid by 

 means of a tube at one end, and which, when squeezed by the hand, drives 

 the contained fluid through a tube at the other end, on account of the 

 presence of a valve, preventing its return through the tube by which it 

 entered the bulb. Here, the tube of entrance is the veins and the auricle • 



