— 102 NATURAL HISTORY OF WASPS. 
insects, just like the central nervous system, connected 
with the sternum or front of the thorax. 
Besides these nerves, which correspond to our 
cerebro-spinal system, and which we can fairly trace 
to a certain extent, there are others,* which we 
cannot trace at all in such minute objects as wasps, 
which represent the sympathetic or organic system 
ofnerves. In these last, as well as in the nerves which 
belong to the cerebro-spinal system, the structure 
throughout is of the simplest kind. There are no 
separate tubes in which the nervous matter is con- 
fined; the cords answering to our nerves consist, not 
of bundles of hollow threads, but of rows of globules 
of nervous matter inclosed in one common delicate 
sheath.T 
The physiology of the nervous system of insects 
is as simple as its structure. Our movements are 
directed by a single brain, a separation of the con- 
nections between which and the rest of the system is 
almost instant death. And so close is the sympathy 
between the nervous centre and the rest of the body, 
that a shock to it, from an injury of an important 
part of the body, is often fatal. Nothing of this 
kind occurs in insects. They have not one only but 
many nervous centres, neither any one of them, nor 
the whole of them together, having the same relative 
importance to the whole body as our single organ 
* T must again refer to Mr. Newport's elaborate essay, ‘ Cyc. Anat. 
Phys. Insecta,’ Vol. II, p 942, for all beyond the most elementary 
statements as to the structure and arrangement of the nervous system 
of insects in this chapter. An excellent summary of what is known 
on this subject may be found in Van Der Hoeven’s ‘ Handbook of 
Zoology,’ Vol, I, pp. 276, 277. 
+ Burmeister. ‘ Entomology,’ translated, p. 270. 
