THE NERVOUS SYSTEM OP THE LOBSTER. 317 



the limb was sharply raised and the claw closed. On stimulating its 

 central end there ensued sharp reflex movements of the thoracic appen- 

 dages, flapping of the abdomen and slight movements of the antennae 

 and masticatory appendages. Also in the most lively animals there 

 was a distinct opening of the claw. 



This experiment shows: (1) that the large nerve contains the motor 

 fibres to the muscles which raise the limb and close the claw ; (2) that 

 this nerve contains many afferent fibres and is hence mixed ; (3) that 

 it contains special afferent fibres which cause opening of the claw by 

 reflex action through the small nerve which alone supplies the divari- 

 cator muscle of the claw. 



Experiment B. — The large nerve being intact the small nerve was 

 ligatured and cut. On stimulating its distal end the claw was sharply 

 opened and the limb extended. On stimulating the central end the 

 claw was closed and the limb raised. In some cases slight movements 

 of the thoracic and abdominal appendages were observed, but in most 

 cases there were no appreciable general movements. 



This experiment shows (1) that the small nerve contains motor 

 fibres which supply the extensor muscles of the limb and especially 

 the divaricator muscle of the claw ; (2) that it contains afferent fibres 

 which cause reflex contraction of the claw through the large nerve 

 which supplies the occlusor muscle. This nerve is therefore mixed 

 also. Thus these two experiments show that each of the two nerves 

 is mixed, and hence separate motor and sensory roots do not exist 

 in the lobster. 



Experiment C. — The following experiment shows that there is a 

 distinct sense of touch in the claws. In an active lobster the eyes 

 and antennae were removed and the animal again placed in the tank. 

 The animal then moved round and round in circles and appeared 

 unable to walk in a straight line unless guided by the side of the tank. 

 When a stick was placed in front of it, it did not grip the stick as it 

 did before the operation, but directly the stick was placed within the 

 claws the latter closed upon it ; thus showing that there is a distinct 

 sense of touch in the claw, in spite of the great thickness and hardness 

 of the calcareotis cuticle. This fact one would presuppose from the 

 large number of nerves which pass to the skin of the claw and which 

 are chiefly derived from branches of the large nerve. 



Experiment D. — Mr. Cunningham found that on placing his finger 

 in the claw after the small nerve was cut he could feel a distinct 



