140 
MR. W. F. barlow’s OBSERVATIONS ON THE 
been free from any source of disturbance ; the room was but faintly lighted ; the 
temperature of the air was 52° Fahr. ; circumstances which would have led me to 
anticipate that it would be in a very sluggish condition. I found it completely quiet, 
and making no respiratory movements which were visible on my first noting it. A 
touch aroused it somewhat, and it began to respire visibly, and to move voluntarily 
for a time or two ; but it soon seemed like a thing half torpid, and ceased to move. 
I continued to observe it : — at one time it made plain respiratory movements ; then, 
the force of these diminished, and they appeared to cease; and this train of circum- 
stances was repeated several times, although great care was taken to maintain 
unchanged all the external conditions in which the insect was placed. 
I afterwards proceeded to try the effects of mechanical irritation of the insect. On 
touching it with a feather between the points where the wings are attached, the 
wings moved rapidly several times ; — I think in an involuntary manner, for I have 
produced precisely such movements, by similar means, in the decapitated dragon- 
fly. At this time the respiratory movements were lively and powerful ; but they 
remained so for only a few seconds. I counted eleven in a quarter of a minute, but 
only three or four very feeble ones in the immediately following half-minute ; then 
they became a little accelerated, but were very soon again impaired, and could not 
be perceived any more for some time. 
An hour later I again watched the insect, which had been kept covered with a glass 
basin. Sometimes the respiratory movements were unseen ; sometimes they were 
very slow and feeble ; sometimes they were quick and strong ; though, all the while, 
the insect did not stir. 
The influence of excitement and mental emotion, mentioned in this observation, 
was again noted in many of the following. In all cases, voluntary efforts and agita- 
tion, of whatever kind, provoke the respiratory movements when they are too faint 
to be observed, and accelerate and strengthen them when they are already evident. 
But that variations of the movements are not wholly due to those of the mental state, 
will appear from the experiments that show similar variations in decapitated insects. 
In like manner, the variations in the respiratory movements, according to the tem- 
perature of the insect, the accelerations with the rise, and the retardations with the 
fall of temperature, may be observed, in some measure, in those that are decapitated. 
Injluence of Decapitation on the Respiratory Movements. 
The effects of decapitation, involving the removal of the supra- and sub-oesophageal 
ganglia (the analogues of the brain and medulla oblongata) of the insect, vary 
accordingly as the head is removed by a sharp instrument, or is suddenly crushed. 
In the latter case, the influence of ‘shock’ is added to that of the removal of the 
ganglia. In the following observations the head was severed with as little violence 
as possible: — 
Exp. ii. Sept. 1, 1845. — •! took a recently caught dragon-fly, and twice counted 
