REFLEX ACTIONS OF ARTICULATA. — 359 
contains a ganglion, will, when separated from the head, set in 
motion its long arms, and impress their hooks on the fingers 
which hold it—Again, aspecimen of Dytiseus (a water- 
beetle), from which the cephalic ganglia have been removed, 
executes the usual swimming motions when cast into water, 
with great energy and rapidity, striking all its comrades to 
one side by its violence ; in these it will persist for half an 
hour, though so long as it lies on a dry surface it remains 
-quiescent. ‘ 
445. From these and similar facts, it appears that the ordi- 
‘nary movements of the legs and wings of Articulated animals 
are of a reflex nature, and are dependent upon the ganglia 
with which these organs are severally connected; whilst 
in the perfect animal they are harmonised, controlled, and 
directed by its conscious power, which acts through the 
cephalic ganglia and the trunks proceeding from it. When 
“we come to compare the refiex movements of Insects with 
those of the higher animals, we shall perceive that there is no 
‘ground for supposing the ganglia of the trunk to be in them- 
selves endowed with sensibility ; so that, when the head is cut 
off, or the cephalic ganglia are removed, or their connexion 
with any part of the body is interrupted by division of their 
nervous cord, no sensation is felt, however much the moye- 
ments ‘a performs may seem at first to indicate this. (See 
§ 467. 
446. From this account of the structure and uses of the 
chain of ganglia in the Articulata, it is obvious that these 
ganglia are so many repetitions of the pedal ganglia (or gang- 
lion of the foot) of the Mollusca ; and we have not yet had 
to notice any ganglia appropriated to other functions. In fig. 
186, however, is seen a small ganglion in front of the cephalic 
mass, which corresponds to the pharyngeal ganglion of the 
Aplysia (fig. 183, D) ; and we have now to describe an entirely 
distinct system of nerves, appropriated to the function of respi- 
ration. As the respiratory apparatus of Articulata, instead of 
being confined to one spot, like that of the Mollusca, is dis- 
_ persed througk the body ($$ 315 and 320), the ganglia which 
: minister to its actions are repeated in the several segments. 
There is, in fact, a chain of minute ganglia lying upon the 
darger cord, and sending off its nerves between those proceed- 
ing from the latter, as seen in fig. 185. These respiratory 
, 
: 
4 
4 
