X 



CIRCULATION OF THE BLOOD. 407 



without being guided by a determinate canal, but, on the contrary, the 

 globules of blood evidently passed between the fatty body and other 

 internal parts. In the vicinity of each aperture of the heart portions 

 of the stream of blood bent over to the heart itself, and upon each 

 expansion passed into it, being received by those apertures. The 

 blood poured forth immediately from parts that were cut off, namely, 

 from the end of the tail, curdling into a thick greenish granulated 

 mass. 



In the larvae of the Agrlons there has been observed the motion of 

 the dorsal vessel, the lateral returning main currents, a stream running 

 upon the entire margin of the rudiments of the wings on the exterior 

 taking its course inwardly and on the interior returning, from which here 

 and there also globules passed in the contiguous passages between 

 the parenchyma of the wings, a powerful current also passes through 

 all the anal leaves, explained as gills, and flows inwardly upon the 

 under side of the central tracheae, but on the upper side again returns ; 

 and, lastly, a stream of blood is observed which advances in throbs, 

 and which probably flows from the anterior aperture of the aorta, 

 bending on each side to the eye, and thence proceeds beneath and back 

 again posteriorly. 



In all perfect insects of this order, namely, in the wings of just- 

 disclosed Libellula (L. depressa) and Ephemerce (E. hitea and mar- 

 ginata) Carus likewise saw a distinct motion of the blood. 



Among the Neuroptera, those larvae which live in water exhibited 

 the same appearances. Distinct contractions were constantly seen in 

 the heart of the caddis-fly larva, which is divided into seven or eight 

 partitions and two lateral returning main streams, whence the globules 

 of blood passed into the apertures between the several chambers. 

 Several perfect insects also of this order, namely, Hemerobius ckrysops, 

 Semblis bilineata, and Semblis viridis, exhibited in their wings, and 

 the latter also in their antennae, a motion of the juices. 



In those larvae which live in water, of many of the Diptera, namely, 

 of the gnats, Wagener observed a distinct pulsation in the dorsal vessel, 

 in which its contraction was visible in several of the chambers of the 

 posterior end. But even those very transparent larvse he observed, on 

 contrary, no motion of the globules of the blood. I myself, notwith- 

 standing having made several experiments, it is true with not very 

 perfect instruments, have been unable to detect such globules of blood. 

 In one instance, and also in a second similar one, namely, in the 



