OF MYRIAPODA AND MACROUROUS ARACHNIDA. 
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experiment on the Lobster. Pressure on the cut extremity of the nervous cord, in 
the posterior half of the body, induced scarcely any movements. When the anterior 
portion of the body, with three or four pairs of legs attached, was separated from the 
posterior, there were acts of progression as in lulus. But the most striking fact was, 
that when that portion of brain which had been removed from the head in connexion 
with the antennal ganglion and antenna was irritated, contractions were immediately 
excited in the joints of the antenna. How difficult to understand is the influence 
of that power which resides in this mysterious centre of all the animal movements ! 
Experiment 14. — The body was divided at a stroke between the second and third 
pairs of legs. Sensation was perfect in the head and two pairs of legs, with which there 
were voluntary attempts at locomotion. But volition and sensation were sooner lost 
than in lulus, and this also was the case with the reflected movements, all which had 
ceased in less than three hours. In each of these experiments on Lithobius sensation 
and volition ceased in the anterior portion of the body in a few minutes, and sooner 
in proportion to the fewer legs connected with the head. Reflex actions continued to 
be manifested longest in the posterior portion of the body in Lithobius as well as in 
lulus, and usually were most readily excited in those regions. 
These experiments seem to lead to the conclusion that the seat of volition is solely 
in the supra-cesophageal ganglia or brain of these animals, since all direction of pur- 
pose, all avoidance of danger, all control over the movements of the body, either of 
speed or change of direction, are lost when these are much injured or removed. Vo- 
lition ceases quickly when they are severely wounded, and is greatly diminished even 
when one only is slightly affected. This latter fact is indicated by the loss or diminu- 
tion of purpose, and by the gyratory movements of the body. The experiments seem 
also to show that sensation may remain after the injury or removal of one lobe of the 
brain, as was proved by the retraction of the antenna when slightly touched on the un- 
injured side of the head, and by the cleansing and excited act of drawing it constantly 
through the mandibles; and further, that pain is felt when the cerebral lobes are in- 
jured, as when the needle was applied to them after the antennae had been removed. 
They lead also to the conclusion, that all the phenomena which occur in the posterior 
parts of the body after the brain and cord have been separated are reflex or excited, 
and that these are most intense at the two extremities of the cord — the medulla oblon- 
gata, and the terminal ganglion ; and further, that the reflex phenomena are always 
excited and do not occur spontaneously, and that their intensity is greater in propor- 
tion to the stimulus applied, and gradually diminishes until they entirely cease, or 
are re-excited, precisely as already shown by Dr. Hall in the Vertebrata. 
The experiments both on the lulus and Lithobius seem further to show, that the 
reflected movements cease first in the anterior part of the cord and its ganglia, and 
that they areretained longest in the posterior; that the movements are most pow- 
erful and continue longest when the cord is entire, the brain alone being separated 
from it; and that they entirely cease sooner in proportion to the greater number of 
