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VETERINARY PHYSIOLOGY 



There is no great shortening in the long axis of the 

 ventricles ; but the auriculo-ventricular grooves are drawn 

 somewhat downwards towards the apex, which does not alter 

 its position. This was demonstrated by Leonardo da Vinci 

 in the living pig by inserting long pins through the chest 

 wall into the wall of the ventricle and observing the 

 movements. 



In systole the ventricles have the form of a truncated 

 cone. 



5. The Cardiac Impulse. 



(1) Cause. — During contraction the heart undergoes, or 

 attempts to undergo, a change in position. In the relaxed 



Fig, 171. — Cardiograph consisting of a Receiving Tambour, with a button 

 on the membrane which is placed upon the cardiac impulse, and a 

 Recording Tambour connected with a lever. 



condition it hangs downwards from its plane of attachment, 

 but when it becomes rigid in ventricular contraction, it tends 

 to take a position at right angles to its base — Cor sese erigere, 

 as Harvey describes the movement. Since the apex and 

 front wall are in contact with the chest, the result of this 



