PHYSIOLOGY OF NERVOUS SYSTEM IN ARTHROPODS. 477 



and ventral surfaces of the ventral chain in Crustaceans ; and 

 Yung says, ' The classical opinion that the inferior surface is 

 sensitive and the superior motor is invalidated by my experi- 

 ments. The nerve-roots are at the same time both motor and 

 sensory.' As no attempt, however, was made by the authors 

 quoted to eliminate reflexes, it is difficult to understand how they 

 could conclude, from the fact that movements occur by stimula- 

 tion of a given tract, that the function of the tract is motor. 



On the other hand, Faivre [171] asserts that by destruction 

 of small portions of the dorsal or ventral surfaces of the 

 ganglia in Dytiscus he was able to produce either motor 

 paralysis or anaesthesia, and proved that the dorsal surface is 

 motor and the ventral sensory in function ; but he insists that 

 these results can only be obtained when the lesions are super- 

 ficial, destruction of the white core gives rise to ambiguous or 

 contradictory results. 



Faivre arrived at the following conclusions : 



a. Sensibility and excitability are distinctly located. The 

 inferior surface of the ganglia is the special seat for afferent 

 and the superior for efferent (motor) impulses. 



b. Paralysis (motor) results, from superficial lesions of the 

 superior surfaces of the pro- and mesothoracic ganglia, in the 

 foot and leg of the same side. 



c. By operating on the infero-lateral aspect of these ganglia 

 sensory impulses, propagated from the corresponding leg, pro- 

 duce no result, but the power of movement remains intact. 



d. A double paralysis of sensation and motion may be pro- 

 duced by appropriate superficial lesions without impairment 

 of the conductive power of the ventral cord to, or from, the 

 ganglia behind the lesion. 



e. Paralysis (motor) is more easily produced singly, i.e., 

 without corresponding anaesthesia, than anaesthesia without 

 motor paralysis. 



6. The ganglionic chain in the Myriopoda (Newport*) con- 



* Newport, G., ' On the Structure, Relations, and Development of the 

 Nervous and Circulatory Systems in Myriopoda and Macrourous Arachnida.' 

 Phil. Trans., 1843. Part ii. 



