3l8 GilmanA.D 



retu 



The pedal ganglia lie in the foot, very near the point where its 

 dorsal border joins the visceral mass, Figs, i and 2, pg. They are 

 more deeply embedded than are the other ganglia, but parts of 

 them may sometimes be seen when the foot is pressed ventrally and 

 posteriorly. To expose them it is necessary to remove the over- 

 lying tissue, which includes a thin layer of muscle. Like the vis- 

 ceral, the pedal ganglia are closely fused and their connecting 

 commissure is covered by ganghon cells. The cerebro-pedal 

 connectives, Fig. 2, cpc, may be seen throughout their extent with- 

 out cutting. Like the other connectives they seem to be free from 

 ganglion cells. The pedal gangha supply the nerves to the foot. 

 From each ganghon three large nerves pass toward the end of the 

 foot and one or two extend ventrally. From the postero-ventral 

 surface of each ganghon a nerve passes posteriorly and laterally 

 to the side of the foot. The pedal nerves are not easily reached 

 without rather extensive dissection and their individual actions 

 have not been studied. As they are the only nerves to the foot 

 they must contain both motor and sensory fibers. 



In stimulating the different gangha directly, it was found that 

 an electric stimulation that could just be distinctly felt by the 

 tongue was most satisfactory as it did not cause mutilation and 

 the results did not give evidence of escaped current. 



With all commissures and connectives intact, the stimulation of 

 any ganghon visibly affected the whole animal, but the relative 

 time of the contraction of different parts differed according to the 

 ganglion stimulated. Thus when the visceral ganglia were stimu- 

 lated, the siphons responded immediately, the collar and anterior 

 adductor muscle later, and the foot shghtly later still. This could 

 be noticed without the use of recording instruments and indicates 

 that an appreciable time is taken in transferring from one set of 

 fibers to another; much longer than in the higher animals. Organs 

 connected directly with the ganglia stimulated always responded 

 first and those that were stimulated through association centers 

 later. 



The majority of the experiments performed were to determine: 

 (i) The organs that received nerves from each pair of ganglia. 

 (2) Whether each pair of gangha individually govern the move- 



