® 
432 THE INSECTA. § 340. 
s 
The Blood of the Insecta is usually a colorless liquid, though sometimes 
yellowish, but rarely red. In this liquid are suspended a few very small, 
oval, or spheroidal corpuscles, which are always colorless, have a granular 
aspect, and are sometimes nucleated. ® 
The Dorsal Vessel, which is constricted at regular intervals, is always 
situated on the median line of the abdomen, being attached to the dorsal 
‘wall of its segments by several triangular muscles whose apices point out- 
wards. Its walls contain both longitudinal and transverse fibres, and, 
externally, are covered by a thin peritoneal tunic. Internally, it is lined 
by another very fine membrane, which, at the points of these constrictions, 
forms valvular folds, so that the organ is divided into as many chambers as 
there are constrictions. Each of these chambers has, at the anterior 
extremity on each side, a valvular orifice which can be inwardly closed.” 
The returning blood is accumulated about the heart and enters into it. 
during the diastole of each of its chambers, through the lateral orifices. 
It then passes, by the regularly successive contractions of the heart, from 
behind forwards into the aorta which is only a prolongation of the anterior 
chamber. This aorta consists of a simple, small vessel, situated on the 
dorsal surface of the thorax, and extending even to the cephalic ganglion, 
where it either ends in an open extremity, or divides into several short 
branches which terminate in a like manner. The length of the dorsal 
vessel depends, in all the three states of insects, upon that of the abdomen. 
The number of its chambers is very variable, but is, most usually, eight.” 
The blood, after leaving the aorta, traverses the body in currents which 
2The blood is red in many larvae of Chzrono- 
mus. 
8 For the blood of Insecta, see Wagner, Zur ver- 
gleich. Physiol. d. Blates, Hft. 1, p. 26, Hft. 2, p. 
3b, and Isis, 1832, p. 323; Horn, Das Leben d. 
Blutes, p. 9, Taf. I. and Newport, Institut. 1845, 
p. 241, or Ann. d. Sc. Nat. III. 1845, p. 364, or 
Froriep’s neue Notiz. XXXIV. p. 9. 
4 For the structure of the dorsal vessel, see 
Straus, Consid. &c. p. 356, Pl. VIII. (Melolon- 
tha vulgaris) ; Wagner, Isis, 1832,. loc. cit, Taf. 
IL. (larvae of Diptera and Ephemeridae), and in 
Miller’s Arch. 1835, p. 311, Taf. V. (larva of 
Corethra plumicornis) ; Newport, Philos. Trans, 
1843, p. 272, and Cyclop. loc. cit. p. 976, fig. 433, 
A. and 434 (Lucanus cervus and Asilus crabri- 
formis); finally Verloren, Mém. loc. cit. p. 31, 
1. ILL-VII. (Chironomus, Sphinx, Rhyncho- 
phorus, Pompilus, Syrphus, and Vespa). The 
worms fed on different artificially-colored leaves 
produced correspondingly colored cocoons. He 
therefore fed, in the same manner, various larvae, 
and, upon dissection, found not only their blood but 
also their tracheae colored like the color used. 
With the tracheae, this color was deepest at the 
hase, but gradually paled away towards their ex- 
tremity. What adds a corroborating value to these 
experiments is the fact that the muscles here re- 
mained uncolored, thus showing that this special 
trachean coloration was not due to a bathing of the 
general fluids of the body. Compare also the re- 
cent various notes and papers of Blanchard, in 
Ann. d. Sc, Nat. — Ep. : 
* | § 340, note 4.] See also, for histological de- 
constrictions of the dorsal vessel are feebly marked. 
with the larvae of the Diptera and Hymenoptera.* 
5 According to Newport (Cyclop. loc. cit. p. 
977), the space in which the blood accumulates. 
about the heart is surrounded by a very thin mem- 
brane, and may therefore be regarded as a true 
auricle. ; 
6 The Aorta is divided at its extremity with 
Meloé, Blaps, Timarcha, Vanessa, and Sphing ; 
see Newport, Cyclop. loc. cit. p. 978. 
7 With the Orthoptera, Lepidoptera, and their 
larvae, as also with various larvae of Diptera. It 
is rare that the number of chambers exceeds eight, 
as, for example, with the Poduridae (WVicolet, loc. 
cit. p. 50, Pl. IV. fig. 3). More commonly there- 
are seven, as with Lucanus and Dytiscus (New- 
port, Cyclop. loc. cit. fig. 433, A., and Wagner, 
Icon. Zoot. Taf. XXITI. fig. 2). Burmeister 
(Handb. I. p. 165) has observed only four with the 
larva of a Calosoma. 
tails upon the heart, Leydig, Siebold and Kél- 
liker’s Zeitsch. 1852, III. p. 446 (larva of Co- 
rethra plumicornis). This naturalist. has here 
described a new and peculiar kind of valves, which 
deserve particular notice. In the last chamber of 
the heart, there are six or eight pairs of roundish, 
clear bodies, attached to the inner surface of the 
heart by apeduncle. They alternate in their posi- 
tion, one beyond the other, so that, during the sys- 
tole, two of them are so opposed that the calibre of 
the chamber is completely closed at that point. 
Each of these curious valves is only a pedunculated 
nucleated cell- see loc. cit. Taf, XVI. fig. 2,¢.— 
Ep. 
