REST OF INSECTS. 403 



Dr Carus has observed the same phenomena in the 

 wings of Scmbds bilincato, and in the ehjtra (wing 

 cases) of Lampuris noctilnca (the glow worm), and 

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

 tail of the larva of Jlgrion pitella (the damsel dragon 

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

 which the circvilation 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 tiuids of insects, 

 agreeably to the original views of Chabrier, or those 

 of Swammerdam form.erly 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., Jan. 1830, p. 49, 

 t See page 343, 



