250 
MR. NEWPORT ON THE NERVOUS AND CIRCULATORY SYSTEMS 
again have occasion to refer to, more especially with reference to the true structure 
of ganglia. The fibres are traceable most distinctly in the lulidse. 
These are the structures to which I formerly assigned the function of voluntary 
motion and sensation, and to which I am still inclined to believe they minister, since 
the fibres of which both are composed are traceable to the crura and brain. Whether 
these functions are restricted separately to the two structures, as 1 first imagined, the 
one to the upper and the other to the inferior series, or whether they are administered 
to conjointly by both, through an interchange of fibres, it is almost impossible to de- 
termine by any decisive experiment on these animals, although the structures them- 
selves are distinct. But in the absence of experimental proof there are circumstances 
connected with the distribution of the nerves to the extremities which seem to indi- 
cate, that these low forms of Articulata are endowed with a power of sensation and 
feeling far beyond what has of late been adjudged to them by some physiologists. 
In some of the gigantic Spirostrepti and Spiroboli the legs are adapted for climbing 
up the trunks and branches of trees, by the under surface of the first and second 
basilar joints of the tarsi being developed into a soft cushion or pad, as in some in- 
sects ; and to these parts of the limbs 1 have found the nervous fibres more extensively 
distributed than to any other ; a fact most strictly analogous to that of the distribu- 
tion of nerves in t fie tactile parts of the limbs of Vertebrata. 
Those fibres of the cord which seem to be independent of the sets just described, 
and which do not appear to have any direct communication with the great seat of 
sensation and volition — the brain, — are of two kinds, which may justly be regarded as 
involuntary in their functions. The first of these are the commissural fibres (figs. 4.5. 
7- g ) which pass through the ganglia ; and the second are those which have hitherto 
been undescribed, and form the sides of the cord ( f ) in the interspace between the 
ganglia, or between certain nerves distributed from them — the fibres of reinforcement 
of the cord. 
The fibres of reinforcement of the cord form the lateral portions of the whole 
nervous cord of the body, and enter into the composition of all the nerves. They 
constitute, as it were, circles of nervous communication between two nerves that 
originate from the cord at a greater or less distance ; and form part of the cord in 
the interval between these nerves, and bear the same relation to the segments, indi- 
vidually, which the cord itself does to the whole body. They form a part of the 
nervous trunks which come off from its upper, or aganglionic tract, as well as of those 
which proceed from the ganglionic enlargements in the lower, and in each instance 
they bound the posterior side of one nerve and the anterior of another, to which they 
proceed along the sides of the cord, forming', in the interspace, a part of its structure. 
Each fibre may thus be traced from its peripheral distribution, in the structures of 
the external surface of the body, inwards, along the course of the nerves, on their 
posterior surface, to the cord, where its direction is altered from that of the nerve 
