$ 310. 383 
THE ARACHNOIDAE. 
arterial trunk. The anterior of these arteries very soon ramifies, and dis- 
tributes blood to the feet, the pincers, the cheliceres, and to all the organs 
in the cephalic extremity. Two of its branches, bending downwards, em- 
brace the cesophagus, and then join in a large common vessel called the 
Supra-spinal artery, which lies upon the ventral cord and accompanies it to 
the caudal extremity, giving off, in its course, numerous lateral branches. 
The posterior arterial trunk is distributed in like manner to the posterior 
extremity, and gives off, right and left, numerous branches. The middle 
chambers of the heart send off, each, laterally, shorter arteries, which are 
distributed to the neighboring organs. Beside these arteries of the muscles 
and viscera, these animals have, also, a special Visceral artery, arising from 
the anterior arterial trunk before it divides into the two branches which 
form the supra-spinal artery. The visceral artery runs backwards towards 
the digestive tube, and sends branches to the liver.” The terminal rami- 
fications of these various arteries are directly continuous, it is said, with a 
venous system.” In this last may be noticed, especially, a Sub-spinal 
vein, by which the blood is carried to the pulmonary sacs; thence to be 
borne to the heart by special vessels. These last open, probably, into a 
sinus, from which the blood passes into the heart through lateral openings, 
two of which exist in each of its chambers.t 
4This supra-spinal artery had been seen, it 
would appear, by Mi/der (loc. cit. p. 62, Taf. I. 
fig. 5, r. r.), but he took it for a ligament. 
5 According to Newport, this visceral artery, 
which is simple with Androctonus, is divided into 
two trunks with Buthus. 
6 Newport speaks in his memoir of various an- 
ti occurring betw the arteries and veins 
with Scorpio. But, as he nowhere describes pre- 
* [ § 810, note 6.] In regard to the question of 
cisely this point, and has not distinctly indicated it 
in his plates otherwise so beautiful, I demur admit- 
ting that, with the Scorpionidae, the arteries pass 
directly into the veins, and therefore, that these 
animals have a system of capillary vessels. This 
direct communication between these two systems 
does not exist with the other Arachnoidae, neither 
with all the other Arthropoda in general.* 
1 
capillaries with the Scorpionidae, « remark of 
Blanchard (loc. cit.) may be given. He says, “I 
have proved with an entire certainty that the blood 
4s distributed in all the cavities of the body, as with 
all the Articulata, and that it is conveyed to the 
Jungs simply by means of the lacunae. Most of the 
vessels which arise from the sides of several of the 
chambers of the heart have appeared to me to be 
fp diac vessels, wholly analogous to those 
we have described with the Araneae.” — Ep. 
t [§ 810, end.} For further details on the cir- 
culatory system of the Arachnoidae, see the 
quoted above of Blanchard. This naturalist has 
sought to extend his doctrine of the peritrachean 
circulation, to the different sections of the Arach- 
noidae. — Ep. 
