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CIRCULATION. 



Observe that contractions follow each other in the order of 

 sinus, auricles, ventricle, and bulb. The ventricle becomes 

 pale and rounded at the systole, each section of the heart 

 diminishing in volume as it empties itself. 



Record the movements by GaskeWs suspension method. 



FIG. 50. Frog-heart recorder. A Aluminium rod, attached to the hinge H and 

 the recording arm. The heart is connected to it by the hanging thread. S Counter- 

 poising spring adjusted by the slider on the vertical rod. F Wooden base clamped 

 to the bracket on the pillar P of the general stand. C Loaded cork frog plate. 

 B Side bar carrying T an electric style. 



A fine silk thread about 1 2 cm long, moistened with normal 

 saline, has a single loop made upon it ; this is slipped over 

 the apex and is tied so as to include the smallest possible 

 portion of the tip. 



This can be done without much difficulty if the ligature 

 be slowly tightened at first around the ventricle until it slips 

 to the exact spot at which it is to be fastened, when it should 

 be drawn tight suddenly. Secure with a second knot. Then 

 place the frog with the frog plate upon the board of the 



