332 ARACHNIDA—ARANEAE CHAP. 
arteries leave the heart, the principal one, or “aorta,” plunging 
downward and passing through the pedicle to supply the cephalo- 
thorax. Besides this, there is a caudal artery at the posterior 
end, and three pairs of abdominal arteries, which proceed from 
the under surface of the heart, and the ramifications of which 
supply, in a very complete manner, the various organs of the 
abdomen. The heart is not divided up into compartments. The 
anterior aorta passes through the pedicle, above the itestine, and 
presently forks into two main branches, which run along either 
side of the sucking stomach, near the front of which they bend 
eae hy 
im ll ase . 
LL’ — 
Ve ee 
PS ReDE ee 
18 
Fic. 186.—Diagram of a Spider, Hpeira diademata, showing the arrangement of the 
internal organs, x about 8. 1, Mouth; 2, sucking stomach ; 3, ducts of liver ; 
4, so-called Malpighian tubules ; 5, stercoral pocket ; 6, anus ; 7, dorsal muscle of 
sucking stomach ; 8, caecal prolongation of stomach ; 9, cerebral ganglion giving off 
nerves to eyes; 10, sub-oesophageal ganglionic mass ; 11, heart with three lateral 
openings or ostia ; 12, lung-sac ; 13, ovary; 14, acinate and pyriform silk-glands ; 
15, tubuliform silk-gland ; 16, ampulliform silk-gland ; 17, aggregate or dendriform 
silk-glands ; 18, spinnerets or mammillae ; 19, distal joint of chelicera ; 20, poison- 
gland ; 21, eye; 22, pericardium ; 25, vessel bringing blood from lung-sae to peri- 
cardium ; 24, artery. 
suddenly downwards and end in a “ patte d’oie,” as Causard ’ 
expresses it—a bundle of arteries which proceed to the limbs 
(Fig. 185). Where the downward curve begins, a considerable 
artery, the mandibulo-cephalic, runs forward to supply the cheli- 
cerae and the head region. We have omitted certain minor 
branches from the main trunks which supply the thoracic 
muscles. The nerve-mass receives fine vessels from the “ patte 
dole.” 
There are no capillaries, but the blood is delivered into the 
tissues and finds its way, by irregular spaces or “ lacunae,” into 
certain main venous channels or “ sinuses.” There are three such 
1 Recherches sur Vappareil circulatoire des Aranéides. Lille, 1896. 
