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VETERINARY PHYSIOLOGY 



position. In the relaxed condition it hangs downwards and 

 to the left 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 movement is to press the 

 heart more forcibly against the chest wall. This gives rise 

 to the eardiae impulse which is felt with each ventricular 

 systole over the prsecordium (fig. 111). 



FIG. 114. 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. 



If the chest is opened and the animal placed on its back 

 this elevation of the apex is readily seen. If the animal is 

 placed on its belly, so that the heart when relaxed hangs 

 forwards, the apex is tilted back during contraction. 



The increased thickness of the heart from before backwards 

 also assists, to some extent, in the production of the impulse. 



In character it is felt as a forward impulse of the chest 

 wall, which develops suddenly, persists for a short period, 

 and then suddenly disappears. 



The cardiac impulse may be recorded graphically by means 



