272 
MR. NEWPORT ON THE NERVOUS AND CIRCULATORY SYSTEMS 
parts into which the cord is separated : further also, that the reflex phenomena are 
less readily excited in the anterior part of the cord, while it is still in connexion 
with the brain, and that they cease entirely soon after the cessation of volition in 
that organ ; as in those experiments in which only a very short portion of cord was 
removed with it from the body. 
Many of the phenomena are precisely similar to those which have heretofore been 
observed in the Crustacea. They agree in the circumstance that violent contractions 
of the segments and limbs, both anterior and posterior to a ganglion, are induced by 
irritation of that ganglion, both when connected with the brain and when insulated 
from it, thus proving these movements, in the latter instance, to be reflex ; but there 
is as yet no direct proof that sensation does not also exist in these ganglia. 
The general results of these experiments tend to confirm the belief that the fibres 
now pointed out in the composition of the cord and ganglia, and which cannot be 
traced to the brain, are those by which these movements are executed independently 
of that organ ; and further also ; that the reflex phenomena are most intense, most 
easily induced, and are of longest duration in those animals of low organization in 
which the volume of brain bears the smallest proportion to that of the whole nervous 
system, in which also volition and sensation are of small amount, and which have the 
body formed of the greatest number of similar uniform parts or segments*. 
2. The Circulatory System. 
The existence of a motion of the fluids in the Articulata has long been known to 
the microscopic observer. So long ago as the middle of the last century it was seen 
by Baker-I" in the limbs of some insects. But notwithstanding this, and the evidence 
of a distinct pulsatory action of the great dorsal vessel, as seen through the tegument 
in the larvse of insects, the existence of a true circulation of the fluids in them and 
some of the neighbouring classes was doubted until the fact was demonstrated by 
Carus^:, and afterwards by Wagner §. Yet the means by which this circulation is 
* While this paper has been passing through the press, I have repeated these experiments, on the functions 
of the brain and cord, with still more conclusive results on the Coleoptera, Orthoptera, Hymenoptera, Neuro- 
ptera, Diptera, and other hexapod insects. The cord was divided between the first and second pair of legs. 
The two posterior pairs of legs were immediately deprived of volition, and exhibited only reflex actions, while 
the anterior pair gave marked indications of being as completely under the influence of volition and sensation 
as in the uninjured animal. The cord was then divided between the first pair of legs and medulla oblongata, 
when these legs also were deprived of volition, and exhibited only reflex actions like the posterior. 
Other experiments made on the brain itself, by removing that organ, or by simply separating it from the me- 
dulla oblongata and cord, without decapitating the insect, fully confirmed the experiments on the Myria- 
poda, in proving that the supra- oesophageal ganglia have the functions of a true brain, and are the sole seat of 
sensation and volition ; and that although, when this organ is removed or is insulated from the cord, a regular, 
combined, and consentaneous series of muscular actions can be excited in the limbs, and locomotion induced, 
these acts are then entirely automatic, and are performed without the intervention of sensation or volition. 
August 29th, 1843. — G. N. 
f On the Microscope, vol. i. p. 130. | Nova Acta Nat. Cur. t. xv. p. 2. § Isis, 1832. 
