Nervous System of the Razor-shell Claui 319 



ments of the organs it supplies with nerves, or whether some of the 

 ganghon are accessory and dependent. (3) Whether all connec- 

 tives carry impulses in both directions. (4) How far it was possi- 

 ble to have impulses transferred through association centers that 

 would not normally be concerned with the impulses in uninjured 

 animals. 



Stimulation of the ganglia directly and of the nerves that leave 

 the ganglia, and stimulation of sensory areas and the nerves that 

 supply the sensory areas were all used. 



In discussing the various nerves that leave the ganglia, mention 

 has been made of the organs they supply, so it is only necessary to 

 summarize here. When the cerebral ganglia are separated from 

 the other ganglia by cutting the cerebro-pedal and cerebro-vis- 

 ceral connectives and the circum-pallial nerves,^ stimulation of the 

 ganglia causes contraction of the anterior adductor muscle, the 

 anterior foot muscles, the collar and at least a portion of the margin 

 of the mantle. The functions of the nerves to the labial palps 

 were not determined. 



When the visceral ganglia are separated from the others by 

 cutting the cerebro-visceral connectives and the circum-pallial 

 nerves, stimulation of the ganglia causes contraction of the siphons 

 and of at least a portion of the mantle margins, and feeble contrac- 

 tions of the posterior adductor muscle. SHght contractions of 

 the posterior foot muscles have also been observed, but as the 

 ganglia lie very near them and no nerves have been found enter- 

 ing them from these ganglia, it seems probable that the shght 

 observed contractions were due to escaped current. The pos- 

 terior adductor muscle when stimlated directly did not contract 

 more than when the ganglia were stimulated. It seems that it 

 does not function much in closing the shell. Its office is satisfac- 

 torily filled by the thickened, united, posterior margins of the man- 

 tle lobes. 



When the pedal ganglia are separated from the others by cut- 



' Although the circum-pallial nerves did not seem to be able to carry impulses from one ganglion to 

 the other, they were cut in these experiments to make sure that the ganglia were isolated. They were 

 cut far from the ganglia that were to be experimented upon, so the effect of their motor fibers could be 

 •determined. 



