$ 340. 
THE INSECTA. 
431 
CHAPTER VI. 
CIRCULATORY ORGANS. 
§ 340. 
The Circulatory System is feebly developed with Insecta, consisting of a 
contractile, articulated Vas dorsale, and a cephalic Aorta. 
The first serves 
as a heart, and the second is a simple conductor of the blood from the heart 
into the body. In both of these vessels, the blood moves from behind forwards, 
and, at its escape from the aorta, traverses the body in all directions, forming 
regular currents which have, however, no vascular walls. 
In this way, it 
penetrates the antennae, the extremities, the wings, and the other appendages 
of the body, by arterial currents, and is returned by those of a venous 
nature. 
All the venous currents empty into two lateral ones running 
towards the posterior extremity of the body, and which enter, through lat- 
eral orifices, the dorsal vessel.” 
1 Swammerdamm, Malpighi, and others of the 
older anatomists, had already formed a pretty exact 
idea of the circulation of the Insecta. But, subse- 
quently, it was entirely abandoned when it was ob- 
‘served that the dorsal vessel was a closed tube, and 
served only as a simple reservoir of the nutritive 
juices. Carus was the first to demonstrate anew 
the existence of a circulation which has since been 
confirmed with all the three stages of insects. See 
Carus, Entdeck. eines einfachen, vom Herzen aus 
beschleunigt. Blutkreisl. in den Larven netzfliiglich. 
Insekt. 1827; Nov. Act. Acad. Nat. Cur. XV. 
part Il. p. 8, Taf. LI.; and Lehrb. d. vergleich. 
Zoot. 1834, p. 687; R. Wagner, Isis, 1832, p. 320, 
778; Burmeister, Handb. &c. I. p. 164, 4363 
Bowerbank, Entom. Mag. I. 1833, p. 239, IV. 1835, 
p. 179 (also in Froriep’s neue Notiz. XX XIX. p. 
149); Tyrrell, Philosoph. Trans. 1835, p. 317; 
Newport, Cyclop. ‘&c. II. p. 980; Milne Ed- 
wards, Ann. d. Sc. Nat. III. 1845, p. 278 ; and 
Quatrefages, Instit. 1845, p. 305. This circula- 
tion carried on by the dorsal vessel, having been 
observed by so many distinguished naturalists, it is 
truly incomprehensible that ZL. Dufour (Recherch. 
sur les Hémipt. p. 272; Recherch. sur les Orthopt. 
p. 287; Ann. d. Sc. Nat. XVI. 1841, p. 10; Mem. 
presentes a l’Inst. IX. p. 595, 601) can persist in 
denying that the dorsal vessel is anything but a 
secretory organ which, according to him, has no 
opening and therefore nothing in common with a 
heart. He cites the authority of Cuvier who was 
ainwilling to accord to the Vas dorsale either the 
name or the functions of a heart (Cuvier, Mém. 
sur la maniére dont se fait la nutrition dans les In- 
sectes, in the Mém. d. |. Soc, d’Hist. Nat. de Paris, 
VII. 1798, p. 34, or Rei’s Arch. V. p. 97). D. 
Dufour adduces, moreover, in support of his erro- 
neous view, the following remark of Carus (Erlau- 
* [ § 340, note 1.) The results obtained by 
Blanchard have been very satisfactorily confirmed 
by Agassiz (Proceed. Amer. Assoc. Advancem. Sc. 
1849, p. 140, also its translation into French in the 
Ann. d. Sc. Nat. 1851, XV. p. 358), who has suc- 
ceeded in distinctly injecting the tracheae by the 
dorsal vessel. These experiments I have had the 
terungst. Hft. VI. p. 8), “In the perfect Insecta, 
whose respiration is performed by a system of 
tracheae traversing the entire body, the circulation 
of blood would be useless.” But to this it may be 
replied, that Carus, by these words, has contra- 
dicted his proper obsérvations ; for he has shown 
that there is a circulation in many perfect insects, 
as is stated not only in the Nov. Act. Nat. Cur., loc. 
cit., but also in the Erlauterungstafeln from which 
the above citation was taken. At all events, the 
proposition of Carus is correct, “ that in insects, the 
blood must come in tact with the atmospheric 
air, which is accomplished by means of the tra- 
chean system.’ But this applies only to the small 
portion of the circulation connected with the respi- 
ratory process ; whereas, the larger portion, des- 
tined for the general nutrition of the tissues, does 
not evidently require the presence of tracheae. The 
presence of a real blood-circulation by means of the 
Vas dorsale, is so easily observed, that the injec-" 
tions of Blanchard are scarcely necessary (Compt. 
rend. XXIV. 1847, p. 870). 
If, in certain species, although transparent, these 
phenomena are not observable, we must not be too 
hasty in denying its real existence, for the blood, 
which is not visible except through its globules, is 
often so poor in these last, as to elude our observa- 
tion. Verloren has recently given a very com- 
plete résumé of what has been done on this subs 
ject, and has added new and confirmatory observa- 
tions ; see Hollaadische Beitr. zu den anat. und. 
physiol. Wissenschaft. I. Hft. 2, p. 220; and Mé- 
moire en résponse a la question suivante : éclaircir 
par des observations nouvelles le phénoméne de la 
circulation dans les Insectes, en recherchant si peut 
la reconnaitre dans tes larves des differents ordres 
dz ces animaux, in the Mém. couronn. par l’Acad 
de Belgique, XIX. 1847.* 
good fortune to witness, and their character was 
such as to leave with me no doubt as to the peri- 
trachean circulation. See, also, the additional evi- 
dence which Blanchard (Compt. rend. Oct. 6, 
1851) has recently furnished of a peritrachean cir- 
culation, which is very important and weighty. 
He took advantage of the well-known fact that silk- 
