MOVEMENTS OF THE EARTHWORM 617 



ing over one or two segments. Having thus gained access to the 

 nerve, a pair of curved forceps, or a bent needle, was brought under 

 it, and by gently lifting the instrument sufficient force was exerted 

 to break the frail connections with the surrounding tissue, causing 

 the nerve to slip out from the body. By this means it was pos- 

 sible to extract even as many as 20 to 25 ganglia at a time; once, 

 indeed, a portion of the ventral chain together with the cerebral 

 ganglia was pulled out. But the method does not meet with 

 equal success in different kinds of earthworms. In Lumbricus 

 terrestris, for instance, where the nerve is too fragile and rigid, 

 it cannot be pulled out, but in Allolobophora foetida the nerve 

 is elastic and the results of the operation are therefore more or 

 less certain. 



The small wound heals over rapidly, but the " nerveless" 

 region can be readily distinguished on account of the strong con- 

 traction of its longitudinal muscles. In fact the latter are in a 

 state of constant and maximum contraction, because the "nerve- 

 less" region remains conspicuous for its diameter even when the 

 adjacent normal segments have contracted. Friedlander having 

 observed the same condition in his worms attributed the exces- 

 sive swelling of the "nerveless" region to a connective substance 

 (ein indifTerentes Narbengewebe) binding the cut muscle-fibers. 

 Since a swelling of the "nerveless" region is invaribly found also 

 in cases where the muscle fibers have not been injured, his inter- 

 pretation is apparently incorrect. 



The complete retraction of the setae, which has been observed 

 in every operated animal, is another peculiarity characteristic of 

 the "nerveless" region of the worm. 



During the first few days after the operation the application of 

 various stimuli, such as irritation with a needle, weak alcohol 

 or electrical stimulation, produces no effect within the "nerve- 

 less" region, but as time goes by the sensitiveness returns slightly 

 and local responses are generally obtained upon stimulation. The 

 secretion of mucus in the "nerveless" region is somewhat lessened, 

 though a strong stimulus may cause an abundant secretion. Usu- 

 ally, however, this portion of the worm is in a condition of greater 

 dryness than the rest of its body but, when stimulated, the exuda- 

 tion of mucus in the furrow between segments may be seen. 



