REST OF INSECTS. 403 



Dr. Carus has observed the same phenomena m the 

 wings of Semhlis hilineata, and in the elytra (wing- 

 cases) of Lampyris noctilvca (the glow-worm), and 

 L. Italica^ as well as in the fin-like appendages at the 

 tail of the larva of Agrion puella (the damsel dragon- 

 fly), in which he first made the discovery, and in 

 which the circulation is remarkably distinct."* 



We apprehend, as far as we can collect from this 

 description, that the alleged discovery of Dr. Carus 

 does not advance a step in demonstrating a circu- 

 lation in insects similar to that of other classes of 

 animals ; for it is to be recollected, that the dorsal 

 vessel, the only organ in insects analogous to a 

 heart, although it pulsates irregularly, has no ap- 

 parent arteries or veins connected with it : and 

 therefore the impulsions described by De Geer, the 

 current mentioned by Baker, and the phenomena 

 exhibited by Carus, furnish no proof whatever of 

 a general circulatory system, though they appear to 

 indicate local movements in the fluids of msects, 

 agreeably to the original views of Chabrier, or those 

 of Swammerdam formerly quoted. f 



It may appear to some, that the preceding has but 

 a very remote connexion with the subject immediately 

 before us ; but we shall presently show its con- 

 nexion with the phenomena of insect sleep. We 

 agree with Professor Blumenbach, that sleep in man 

 most probably consists in a diminished or impeded 

 flow of arterial blood into the brain. For example, 

 if, by cold feet, a fit of passion, or a heavy supper, 

 a gush of blood is forced into the brain and stag- 

 nates there, the consequence will be the snoring 

 death-like sleep of apoplexy ; and the same will 

 happen, if a blow on the head, or a fever, throws 

 a quantity of blood upon the brain. Blumenbach 



* Spence in Mag. of Nat. Hist., .Tan. 1S;]0, p. 19. 

 t See page 3i.'3. 



