THE HOESE. 



157 



HEAKT. 



Q. What is the form of the heart ? — A. Its form is 

 conoid, yet somewhat flattened on the anterior sm-face 

 and rounded on the other. 



Q. Where is the heart situated? — A. Witliin the 

 thorax, in the region of the fourth, fifth, and sixth 

 dorsal vertebrae ; bounded on the sides by the limgs 

 and walls of the thorax ; posteriorly, by the dia- 

 phragm; inferiorly and anteriorly, by the sternum. 



Q. How is the body of heart divided .^ — A. Into a 

 base and apex. 



Q. What are the divisions internally .►' — A. It is 

 divided into four cavities, viz : two auricles, or anterior 

 cavities ; two ventricles, or j^ostei'ior cavities. 



Q. What communications exist between the cavities 

 of the heart? — A. Between the two auricles there is 

 no communication, nor between the two ventricles ; 

 but the right auricle opens into the right ventricle, and 

 a similar opening exists between the left amicle and 

 ventricle. 



Q. How do veterinarians describe the relative situa- 

 tion of the cavities of the heart? — A. The amides are 

 described as anterior and posterior, because the right 

 auricle forms the upper and fore part, and the left is 

 in a posterior direction ; the ventricles being located 

 imder their respective auricles,- thus we have the ante- 

 rior and posterior ventricles. 



Q. How is the exterior surface of the heart pro- 

 tected ? — By a duphcature of the pericardium. 



Q. What is the function of the auricles? — A. To 

 receive the blood from the various vessels and transmit 

 it to the ventricles. 



Q. What is the function of the ventricles? — A. 

 One propels the blood to the lungs, for purification ; 

 the other distributes it thi-cugh the arterial ramifi- 

 cations. 



Q. Name the venous vessels wliich terminate in the 

 right auricle. — A. Three venous vessels terminate in 

 it, viz : the vena cava, anterior and posterior, and the 

 coronary vein j the vena azygos forms a junction with 



the anterior cava, just as the latter pierces the walls of 

 the auricles. 



Q. How are the am-icles di^ided ? — A. By the sep- 

 tum auricularum. 



Q. Describe the internal mechanism of the right 

 ventricle? — A. It has within it numerous fleshy pil- 

 lars, longituchnally distributed; also, three fleshy 

 prominences, termed carnea columnae, from which sev- 

 eral tendmous cords proceed to the edges of those 

 membranous and fibrous productions ; these close the 

 auriculo-ventrlcular opening; the apparatus alto- 

 gether forms valvula tricupsis. Other cords, similar to 

 the cordae tendinse, pass between the outer wall and 

 the septum. 



Q. Where is the origin of the right pulmonary ar- 

 tery? — A. It emerges from the upper and back part 

 of the ventricle. 



Q. How is the mouth of this artery protected ? — A. 

 By three semilunar valves, wiiich present little pouches 

 within its cavity ; these valves consist of doublings of 

 the lining membrane of the parts. 



Q. Describe the left ventricle? — A. Its cavity is 

 smaller than that of the right, and its wall is thicker. 

 Its musculi pectinati appear mostly upon the septum, 

 within the apex and under the valves ; it has two, in- 

 stead of three, carnse columnae ; they are more bulky, 

 and project more into the ca\ity than those of the 

 right. 



Q. From whence does the aorta arise? — A. From 

 the upper and fore part of the left ventricle. 



Q. What is remarkable about the mouth of the 

 aorta ? — A. It has thi-ee semilmiar valves, similar to 

 those at the origin of the pulmonary artery. 



Q. By what are the ventricles dinded ? — A. They 

 are divided by a fleshy joartition called septum ventric- 

 ulorum. 



Q. How is the circulation of the blood effected ? — 

 A. By the alternate contraction of the auricles and 

 ventricles, called the dyastole and systole of the heart. 



Q. By what vessels is the heart itself suppHed with 

 blood? — A. By the coronary arteries. 



