RESPIRATORY MOVEMENTS OF INSECTS. 
141 
its respiratory movements; they were at the rate of sixty-four in a minute. I then 
separated the head of the insect with a sharp knife. There ensued convulsive move- 
ments of the body, and gaspings of the head : the respirations were fifty in the minute; 
but after the lapse of four minutes, they were reduced to thirty-eight, and after four 
more minutes to thirty-five ; the respiration was performed more feebly than just 
after the head’s removal ; and in ten minutes it was reduced to thirty-one times in 
the minute. During all this time the insect was still, unless it was touched; then 
movements of the wings ensued. Faeces were spontaneously passed. 
I now left the insect, and on returning in an hour, found the respirations in num- 
ber as before, and quite as powerful. It lay in a tranquillity in which no motions but 
those of its breathing could be seen, and to one unobservant of the removal of the 
head, it would have seemed as if sleeping. Faeces were occasionally passed. Four 
hours later the breathing was feebler, its number being the same : the gaspings of 
the separated head, when it was touched, had less vigour ; on my drawing a feather 
lightly over the surface, the legs retracted ; slight movements of the wings also could 
be thus occasioned. 
Fourteen hours elapsed before I renewed my observations. The insect was now 
respiring at the rate of twenty-six in the minute. Reflex movements could be yet 
excited in the body, but the head was quiet in spite of stimulus. In six hours more, 
the respiratory movements were still twenty-six, and regular. Eighteen hours later, 
they were still discernible, though very faint. 
Exp. iii. Oct. 2. — I counted the respirations of a dragon-fly when it was tran- 
quil, and found them 108 in the minute. I removed the head, and found them forty. 
Ten minutes afterwards they were fourteen : they were quite equable, and continued 
at this rate for some time longer. 
Exp. iv. — The respiratory movements of another insect were sixty. On the head 
being removed they were twenty-five, and most regular. Ten minutes passed, and 
they were fifteen. Half an hour later they were seventeen, and feebler. In another 
instance they were reduced, on decapitation, from sixty-six to twenty-nine. 
The foregoing experiments show that the effect of decapitation is always to dimi- 
nish the frequency of the respiratory movements of the insect. They are confirmed 
by those which follow; but these prove other facts also ; and first, that the irregula- 
rities in the mode and rate of breathing, which are noted in the natural respiration 
of the insect, are equally observed after decapitation, and are therefore not to be 
assigned to the will, or any mental state. 
Exp. V. — On a day when the temperature was 59° Fahr., I counted the respirations 
of a cricket, in several minutes, with intervals of a quarter of a minute between each 
two. They were 84, 106, 79, 64, 59, 90. On the head being removed, they were 19, 
27, 28, 20, 19, 14 ; and were less vigorous. 
Exp. vi. — In a temperature of 52° Fahr., the respirations of another were counted 
like those of the last, and were 90, 70, 73, 72, 50, 62, and unequal in force as well as 
MDCCCLV. 
X 
