CIRCULATION AND RESPIRATION 



55 



90 



80 



70 



60 



50 



40 



E 



<D 30 



20 



Hirudo 



Haemopis 



• / G. complanata 



■ • • Piscicola 



J il 



10 15 20 25 30 35 



Temperature, °C 



Fig. 28. Rate of making respiratory movements by various 

 leeches at various temperatures. Redrawn from Herter, 1936-9. 



is even more striking if we consider the effects of drugs. In 

 Hirudo the accelerating effect of the anterior segmental nerve 

 is abolished by ergotoxin while the slowing effect of the posterior 

 nerve is abolished by curare. Injection of adrenalin increases the 

 rate of pumping, while muscarin decreases it. Schwab (1949) 

 found that adding acetylcholine to water surrounding Erpohdella 

 caused speeding up which was maintained for about half an hour, 

 after which there was a period of depression. Atropine, on the 

 other hand, slowed the contractions. These effects are very 

 similar to those found in mammals and indeed in many vertebrate 

 hearts, but are quite different from the state of affairs in any other 

 invertebrates. In most arthropods and annelids, for instance, 



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DOS //, 



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