CIRCULATION OF THE BLOOD 81 



CHAPTER II 



ON THE MOTIONS OF THE HEART AS SEEN IN THE DISSECTION 

 OF LIVING ANIMALS 



IN the first place, then, when the chest of a living animal 

 is laid open and the capsule that immediately surrounds the 

 heart is slit up or removed, the organ is seen now to move, 

 now to be at rest; there is a time when it moves, and a 

 time when it is motionless. 



These things are more obvious in the colder animals, such 

 as toads, frogs, serpents, small fishes, crabs, shrimps, snails, 

 and shell-fish. They also become more distinct in warm- 

 blooded animals, such as the dog and hog, if they be atten- 

 tively noted when the heart begins to flag, to move more 

 slowly, and, as it were, to die: the movements then become 

 slower and rarer, the pauses longer, by which it is made 

 much more easy to perceive and unravel what the motions 

 really are, and how they are performed. In the pause, as 

 in death, the heart is soft, flaccid, exhausted, lying, as it 

 were, at rest. 



In the motion, and interval in which this is accomplished, 

 three principal circumstances are to be noted: 



1. That the heart is erected, and rises upwards to a point, 

 so that at this time it strikes against the breast and the 

 pulse is felt externally. 



2. That it is everywhere contracted, but more especially 

 towards the sides so that it looks narrower, relatively longer, 

 more drawn together. The heart of an eel taken out of the 

 body of the animal and placed upo^ the table or the hand, 

 shows these particulars ; but the same things are manifest in 

 the hearts of all small fishes and of those colder animals 

 where the organ is more conical or elongated. 



3. The heart being grasped in the hand, is felt to become 

 harder during its action. Now this hardness proceeds from 

 tension, precisely as when the forearm is grasped, its ten- 

 dons are perceived to become tense and resilient when the 

 fingers are moved. 



4. It may further be observed in fishes, and the colder 

 blooded animals, such as frogs, serpents, etc., that the heart. 



