DISEASES OF THE HEART AND BLOOD-VESSELS. 



By M. R. TRUMBOWER, V. S., Sterling, 111. 



REMARKS ON THE ANATOMY AND PHYSIOLOGY OF THE HEART AND 



BLOOD-VESSELS. 



The heart is a hollow, involuntary, muscular organ, situated as 

 nearly as possible in the center of the chest, though its impulse is felt 

 on the left side from the rotary movement of the organ in action. It 

 is cone-shai)ed, with the base upwards; the apex points downwards, 

 backwards, and to the left side. It extends from about the third to 

 the sixth ribs inclusive. The average weight is about Gw pounds. In 

 liorses used for speed the heart is relatively larger, according to the 

 weight of the animal, than in horses used for slow work. It is sus- 

 pended from the spine by the large blood-vessels, and held in position 

 beloAV by the attachment of the pericardium to the sternum. It is 

 inclosed in a sac, the pericardium, wliich is composed of a dense, 

 fibrous membrane, lined by a delicate serous membrane, which is 

 reflected over the heart; the inner layer is firmlj^ adherent to the 

 heart, the outer to the fibrous sac, and there is an intervening space 

 known as the pericardial space, in which a small amount of serum — 

 a thin translucent liquid — is present constantly. 



The heart is divided by a shallow fissure into a right and left side; 

 each of tliese is again subdivided by a transverse partition into two 

 compartments, which communicate. Thus there are four cardiac 

 cavities, the superior or upper ones called the auricles, the inferior or 

 lower ones the ventricles. These divisions are marked on the outside 

 by grooves, which contain the cardiac blood-vessels, and are gener- 

 ally filled with fat. 



The right side of the heart may be called the venous, the left the 

 arterial side, named from the kind of blood which passes through 

 them. The auricles are thin-walled cavities placed at the base, and 

 are connected with the great veins, the vena cav?e and pulmonary veins, 

 through which they receive blood from all parts of the body. The 

 auricles communicate with the ventricles each by a large aperture, 

 the aitriculo-venfricvlar orifice, which is furnished with a remarkable 

 59(31 — HOR 8 225 



