
1890.] Autotomy in the Crab. 139 
cesophageal ganglion) is removed, the self-amputation may still 
be brought about: the same result follows when the brain is 
thrown out of the experiment by anzsthetizing the animal with 
ether or chloroform, 
Peripheral stimuli may be applied to the limb in various ways 
in order to bring about autotomy; thus crushing or cutting the 
segments of the leg (unless it be the terminal ones) is very soon 
followed by the falling off of the leg at a definite point near the 
body, while alcohol, etc., heat, or electric shocks applied to the 
limb produce the same result. In the latter case the time between 
the application of the shock and ‘the resulting autotomy was 
measured and found to vary much. 
The centre for the reflex throwing off of the legs is in the 
thoracic ganglion mass, since the removal of this mass destroys 
the autotomy, and since in one case electric stimuli applied to this 
mass brought about the ordinary autotomy! 
Concerning the mechanisms by which the impulse going out 
from this centre is able to bring about the remarkable rupture of 
the limb at a definite place, the author points out the existence of 
a special groove around the limb of the crab, on the second seg- 
ment from the body, and that this segment is moved in two di- 
rections by two muscles, raised upward by an extensor and 
brought downward by a flexor muscle. These two muscles are 
attached to the upper and lower borders of the second segment 
at the end towards the first, and pass into the first. When auto- 
tomy takes place the limb separates by a clear-cut plane passing 
across the second segment through the above groove ; the stump 
or first segment, with a small ring from the second, is now held 
forcibly in an elevated position. Experiment shows that the 
flexor may be cut without destroying the power of autotomy, 
while when the extensor is cut autotomy does not take place. 
The action of the extensor muscle in autotomy, the author ex- 
plains as follows, with the use of the diagram reproduced in Fig. 
1. The stimulus coming from the leg to the thoracic centre re- 
-sults in the sending out of stimuli to the muscles of the leg, the 
strong contraction of the extensor (ex) brings the leg forcibly 
against the carapace (c) or the fingers of the experimenter, etc., 
