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EX PEKLM ENTA L H I YSIOLOG Y 



CHAPTEE XIII 



SOME FURTHER METHODS FOE EXAMINING THE ACTIVITY OF THE 

 FROG'S HEART 



The student must become familiar with some of the other methods 

 which are employed for recording the heart movements other than 

 the suspension method. 



Experiment 1. — Take a record of the beat of the ventricle by means of one 

 of the recording levers represented in fig. 69. The foot of the vertical rod h 

 is to be arranged to lie on the ventricle, and will thus rise and fall with 

 increase and decrease of thickness of the ventricle. 



During diastole the ventricle wall becomes flaccid, and thus under the 



Fig. 105. — Tracings Recorded by a Lever Resting upon a Frog's Heart. In 

 Tracings i and ii the Lever Rested upon the Ventricle ; in hi and iv 

 upon the Junction of Auricles with Ventricle. Time Tracing Seconds. 



influence of gravity acting on its own substance and of the weight of the 

 lever it becomes flattened. With each systole the ventricle hardens and 

 becomes circular in section, and thus lifts the recording lever. If the ampli- 

 tude of the record be small, it generally means that the pressure of the lever 

 on the heart is too great, and this may be relieved by fixing a wire to the 



