Bauhaus-Universität Weimar

Titel:
The Cyclopaedia of Anatomy and Physiology, vol. 2: Dia-Ins
Person:
Todd, Robert Bentley
PURL:
https://digitalesammlungen.uni-weimar.de/viewer/image/lit25760/971/
INSECTA. 
963 
Fig. 420. 
1 2 S 
Immediately 
after changing 
to a pupa. 
Half-an-hour 
before 
e-hanging. 
Full-grown 
larva. (Newport, Ph. Trans.) 
there is great excitement throughout the body of 
the insect. About half-an-hour (fig. 419, 2) 
before this occurs the alary nerves and the 
cerebral, second, third, fourth, and fifth ganglia 
are slightly enlarged, and the medulla or first 
sub-cesophageal ganglion very considerably. The 
cords that extend between them diverge much 
from each other, while those between the fifth, 
sixth, and seventh ganglia, are disposed in a more 
zig-zag direction than in other parts of the body. 
Immediately after the insect has entered the 
pupa state (3), all the ganglia are brought 
closer together in consequence of the cords 
being disposed more irregularly than at any 
other period, which has been occasioned by the 
shortening that has taken place in every seg¬ 
ment, by which the cords are rendered too long 
to lie in a direct line. The cords which con¬ 
nect the first five ganglia are slightly increased 
in size, and the fourth and fifth and their inter¬ 
vening cords, in which the first great changes 
commence, are often nearer together, and have 
become more united at this period of the trans¬ 
formation, in some specimens, than in others 
at five or six hours later. This is in accord¬ 
ance with what we have observed in the Sphinx 
ligustri, in which the precise period when the 
union of ganglia takes place cannot positively 
be ascertained in consequence of its differing 
in different specimens according to the vigour 
of the insect, or to the temperature of the 
season at the time of changing. 
One hour after (fig. 421, 4) the transform- 
Fig. 421. 
4 5 6 
One hour after Twelve hours. Eighteen hours, 
changing. 
ation the cerebral ganglia are found to be more 
closely united, the antennal nerves more dis¬ 
tinct, and the optic nerves more enlarged at 
their base. The fourth and fifth ganglia are 
approaching each other, and the cords are en¬ 
larged at their connexion with the latter, the 
anterior part of which has become less dis¬ 
tinct, and seems about to coalesce with them. 
The distance between the remaining ganglia is 
also reduced, and the investing membrane, or 
exterior surface of the cord exhibits a corrugated 
appearance as if in the act of becoming 
shortened. We have seen in the account pre¬ 
viously given of the nervous system in the 
larva of the Sphinx, that besides the longi¬ 
tudinal cords and ganglia, and the nerves dis¬ 
tributed from them, there are also the trans¬ 
verse nerves. There are like nerves in Papilio 
urtica:, and which are distributed to the same 
parts as in the Sphinx. They commence be¬ 
hind the first sub-cesophageal ganglion or me¬ 
dulla, where the first of them pass directly out¬ 
wards in the course of the tracheæ that come 
from the first spiracle, and distribute and give 
some branches to the surface of the medulla 
and its nerves, and some also to the second 
ganglion (d), while the main branch passes 
along in the direction of the muscles of the 
back part of the head. Behind the second 
ganglion branches of tracheal vessels, and 
also a nerve from the transverse plexus, are given 
to the great alary nerve ( / ) that arises in this 
insect singly from the cord between the second 
and third ganglion, and not, as in the Sphinx, 
one portion fiom the cord and another from the 
ganglion posterior to it. From the cord be¬ 
tween the third and fourth ganglion arises the 
second alary nerve (i), which like the preceding 
arises singly from the cord, but receives also a 
* 1832. 
3 r 2
        

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