BODY FLUIDS AND CIRCULATION 



109 



Acetylcholine and pilocarpine have a vagomimetic action (Fig. 3.13) and 

 are blocked by atropine (p. 440). It has been observed that the inhibitory 

 potentialities of these drugs are not realized in fish embryos (Fundulus) 



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Fig. 3.12. Effect of Stimulation of the Vagus Nerve 

 on the Heart of Scyliorhinus canicula 



Time scale, above, 1/sec; stimulation shown on second line from top. Lower two 

 curves, heart contractions; auricle above, ventricle below. Some sinus activity is manifest 

 during vagus-arrest of the auricle. (From von Skramlik (119).) 



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ISH 



Fig. 3.13. Effect of Drugs on the Fish Heart (Squalus acanthias) 

 1: adrenaline (1 x 10~ 8 ); 2: noradrenaline (5 x 10~ 7 ); 3: acetylcholine (5 x 10~ 7 ) 

 (heart sensitized with physostigmine 4 x 10~ 5 ). (From Ostlund (97).) 



until the heart is innervated. There is no sympathetic acceleratory supply, 

 either in selachians or teleosts. Evidence dealing with the effect of adrena- 

 line has been rather conflicting. Adrenaline and noradrenaline usually 

 accelerate the elasmobranch heart and increase the force of beat {Squalus, 



