406 PHYSIOLOGY. 



Accor,i' n g to Herold, the dorsal vessel of a full-grown caterpillar, in a 

 temperature of from 16 20 Reaum., made from 30 to 40 pulsations 

 in a minute, but sank in a temperature of from 10 12 down to from 

 6 to 8 pulsations in the same time. In younger caterpillars, the pulsa- 

 tions of the dorsal vessel, under similar circumstances, were quicker, 

 namely, from 46 to 48 times in a minute, in a temperature of 18, 

 whereas in greater heat and with a quicker motion, in conjunction with 

 great exertion, the rapidity of the pulsations still further increases, but 

 they then appear so irregular and numerous, that no positive number 

 can be given. According to Suckow*, the heart of the pine caterpillar 

 ( Gastropacka pint) beats 30 times in a minute, but sinks down during 

 the pupa state to 18 pulses in the same space of time. In the just 

 disclosed caterpillar the pulsation is slow and irregular, but subse- 

 quently its rapidity increases so much, that it then makes from 50 to 60 

 pulses in the minute. Herold says that the pulsations of the butterfly 

 increase the moment it commences to strike with its wings, and purposes 

 flying off, whereas he observed during copulation no alteration of its 

 quickness. 



240. 



The assertion of a motion of the juices is founded upon observations 

 made upon the following insects. 



Among the Dictyolopfera, all such larvae as live in water exhibit 

 it very distinctly. In the larva of Ephemera, a motion of the globules 

 of the blood has been observed in all the peripheric parts, which., 

 according to Wagener, extend even to the last joints of the antennae 

 and of the feet. This motion was slower the more the water evaporated 

 in which the larva was contained, but increased again upon the addition 

 of fresh water. The stream of all the peripheric parts collect into two 

 chief currents, which pass backwards on each side of the body, and send 

 off other currents to the exterior margin of the segments, but which 

 speedily return to the main branch after having passed through the 

 branchiae there situated f. Vessels inclosing these streams have never 

 been observed, and, indeed, the frequently partial change of course 

 distinctly proved the total deficiency of such organs. Individual cur- 

 rents have also been observed to extend even above and beneath the 

 intestinal canal, and to bend over to the main stem of the opposite side 



* Anatomisch-physiol. Unters. tiber Insekten und Krustenthiere, p. 37. 

 f Cams in the Nova Acta 1'bys. Med. vol. xv. Pt. 2, p. 8. 



