190 CIRCULATION. 



chest, the organ was rapidly removed, placed upon the table, 

 and confined by two long needles passed through the base, 

 pinning it to the wood. It contracted for one or two min- 

 utes; and at each systole, the ventricles were manifestly 

 shortened. The point was then placed against an upright, 

 and it receded with each systole about an eighth of an inch. 

 This phenomenon was apparent to all present. 



In another experiment, performed a few weeks later, the 

 heart, which had been exposed in the same way, was exam- 

 ined in situ by pinning it with two needles to a thin board 

 passed under the organ. The presence of these needles did 

 not seem to interfere with the heart's action, and at each 

 ventricular systole the point evidently approached the base. 

 To render this absolutely certain, a knife was fixed in the 

 wood at right angles to and touching the point during the 

 diastole, and a small silver tube was introduced through the 

 walls into the left ventricle. At each contraction, a jet of 

 blood spurted out through the tube, and the point of the heart 

 receded from the knife about an eighth of an inch. The 

 animal experimented upon was a dog a little above the me- 

 dium size. 



These simple experiments demonstrate that, in the dog 

 at least, the ventricles shorten during their systole. The 

 arrangement of the muscular fibres is too nearly identical in 

 the heart of the warm-blooded animals to leave room for 

 doubt that it also shortens in the human subject. 



The error which has arisen in this respect, and which 

 obtained in our former experiments, is due to the locomotion 

 and protrusion of the entire organ, so as to make the point 

 strike against the chest. A little reflection indicates the 

 mechanism of this phenomenon. During the intervals of 

 contraction, the great vessels, particularly the aorta and pul- 

 monary artery, which attach the base of the heart to the pos- 

 terior wall of the thorax, are filled, but not distended, with 

 blood ; at each systole, however, these vessels are distended 

 to their utmost capacity ; their elastic coats permit of con- 



