232 RESEARCH SEMINAR. 



hibitory and accelerator fibres from the same nerve as the auricle. 

 These fibers enter the ventricle at the aortic end, some fibers 

 reach the ventricle also through the walls of the auricle. The 

 ventricle of Limax appears to be supplied with inhibitory nerves 

 only, which enter it through the auricular walls. The ven- 

 tricle of Ariolimax is supplied with accelerator, and probably 

 also inhibitory fibres from the same source as the auricle. The 

 fibres enter the ventricle at the aortic end. In Helix the in- 

 fluence of the inhibitory fibres on the ventricle, in Ariolimax that 

 of the accelerator, is the greatest. 



The systemic and the gill hearts of the cephalopods (Octopus, 

 Loligo, Ommastrephes) are supplied with inhibitory fibres from 

 the visceral nerves, and there is some evidence that accelerator 

 fibres reach these hearts from the same source. In the squid 

 the fibres to the systemic ventricle and to the auricles leave the 

 visceral nerves at different levels. The rhythmically contracting 

 parts of the renal veins are probably supplied with inhibitory 

 fibres from the visceral nerves. The visceral nerves also send 

 fibres to the pulsating vena cava. Their function was not made 

 out. 



The heart of crustaceans is supplied with inhibitory and accel- 

 erator fibres from the thoracic ganglion. In Paliminis the inhibi- 

 tory and the accelerator fibres reach the heart along two separate 

 pairs of nerves. 



The heart of Limulus is supplied with inhibitory nerves from 

 the posterior end of the brain or pericesophageal ganglion, and 

 with accelerator nerves from the abdominal ganglia. These 

 nerves enter the nerve-cord on the dorsal side of the heart. 

 There is some evidence that the heart of spiders and insects is 

 supplied with inhibitory nerves from the brain or the thoracic 

 ganglia. 



2. The action of the inhibitory nerves on the invertebrate 

 heart is the same as the action of the vagus fibers on the verte- 

 brate heart. The accelerator nerves in the molluscs produce 

 contractions in the quiescent heart. Single induced shocks ap- 

 plied to the cardiac nerves are usually without influence on the 

 heart unless of considerable intensity. 



3. The latent period of the heart-muscle is less than 0.03" in 



