THE HEART. 



103 



sum, the tricus- FlG> 



pid valve. The left 

 heart, at the os- 

 tium arteriosum, 

 has the mitral 

 valve. For fur- 

 ther description 

 see organs of cir- 

 culation. 



The heart, ar- 

 teries, and veins, 

 are the three great 

 and fundamental 

 links in the hu- 

 man adult circu- 

 lation, each of 

 which is dependent upon the other, and to strike out 

 either would destroy the entire function. Notwithstand- 

 ing each of these parts has its own proper and especial 

 duty to perform, in carrying on the circulation, still, there 

 are some who limit this action to one or more parts, and 

 deny the rest any share in its performance. 



The heart, for instance, was supposed by Harvey, the dis- 

 coverer of the circulation, and others, to be the sole agent 

 in this function, and that it was accomplished by means 

 of its muscular structure. Hence the various calculations 

 that have been made of the power of the heart's contraction. 

 Borelli estimated it at 180,000 pounds, while Reil only 

 made it from 5 to 8 ounces. These are the two extremes 

 very wide apart and unsatisfactory, the former be- 

 ing sufficient to rend the body in atoms, the latter too 

 feeble to be thought for a moment sufficient to drive the 

 blood from the heart to every part of the body, and then 

 back again to the heart. Hence Bichat introduces the ca- 

 pillaries to supply the deficient power of the heart. Dr. Barry 



FIG. 11 represents the heart double. 1, 1 Superior and inferior cava. 

 2 Right auricle. 3 Right ventricle. 4 Pulmonary artery. 5 Branches 

 from arch of aorta. 6 Left auricle. 7 Left ventricle. 8, 8 Aorta. 



