144 
MR. W. F. BARLOW’S OBSERVATIONS ON THE 
shock beginning to subside, they became apparent. In ten minutes they were more 
feeble but plain, and could be observed in both divisions. I could not succeed in 
counting those in the upper half ; but fifteen minutes later they were fifty in the 
lower half. Two hours and a half after the segmentation, the respiratory movements 
were still visible. 
Exp. XV. Oct. 14. — I counted the respiratory movements of a dragon-fly, of the 
same kind and size as the last. They were only sixty ; and the difference is curious ; 
for the two insects were caught together, and examined in the same manner, and in 
the same hour. On removing the head, the respirations were reduced to forty, and 
became mueh less distinct. The abdomen was bisected, and the respiratory move- 
ments ceased in it. In ten minutes they were renewed, but most faintly and slowly, 
and in the lower half alone. On breathing on the upper half, it contracted languidly 
for a few moments and then became motionless again. 
Exp. xvi. June 29, 1846. — At a quarter before 2 p.m. I ascertained the respirations 
of a dragon-fly, while it was calm and at rest, to be thirty-two. Then I removed 
the head, and involuntary movements of the body, wings, and legs were noticed, 
which in a little while ceased, but were renewed, at pleasure, by excitation. In five 
minutes the respirations were reduced to twenty-eight, and were less powerful. The 
abdomen was now divided into three equal parts, two complete segments being in 
each. The respiratory movements were well-marked in both the upper divisions, 
most strongly in the uppermost ; in the lowest, or caudal division, they were not ob- 
servable. In the uppermost division of the abdomen, the respirations were at the 
rate of thirty-two ; in the middle division, at the rate of forty-eight in the minute ; 
in the caudal division, they were not excited even by breathing on it. 
At half-past two the respiratory movements in the parts of the abdomen were 
feebler ; in the thoracic division, they were still twenty-eight ; in the middle division, 
fifty-two. At half-past three, the only respiratory movements discernible were those 
of the upper division ; but they were much weaker and only twenty-four. Powerful 
respiratory contractions M'^ere excited by very lightly drawing a sharp point down the 
dark mesial line of the abdomen ; and an incurvation of the body, and a peculiar 
movement of the legs towards the part irritated, were observed. At a quarter past 
seven the respiratory movements had ceased, but were renewed, though faintly, by 
breathing on the upper divisions of the abdomen. It was not easy to say why the 
caudal division did not respire, for its excito-motory power was not extinguished ; 
it could be excited to motion, and fseces were expelled by it. 
Exp. xvii. — The subject of this experiment was a lively dragon-fly, which breathed 
at the rate of thirty-five. The head was removed, and the respirations, which did not 
pause perceptibly, were forty-two. In five minutes, the respirations being at the 
same frequency, the abdomen was divided into three nearly equal parts. The caudal 
division breathed powerfully; the thoracic feebly; the middle one not at all. I 
placed this motionless part in my hand ; in ten minutes it revived, and breathed at 
