282 
MR. NEWPORT ON THE NERVOUS AND CIRCULATORY SYSTEMS 
larger ones that pass upwards to the dorsal surface of the body. This is the 
general distribution of the systemic arteries, their anterior branches ( k ) are given 
chiefly to the viscera, and their posterior (i) to the sides of the segments and dorsal 
surface. 
The vascular collar (fig. 18. p, q, r) around the oesophagus is formed by the ante- 
rior pair of systemic arteries. These pass off from the front of the small anterior 
chamber of the heart (1.) at its termination in the basilar segment of the head (b), 
where this organ becomes divided into three trunks, as I have already shown in the 
Chilognatha, and have distinguished them from the other systemic arteries, as the 
aortic arches , from the great analogy which they bear to the connexions between the 
heart and its aorta in many of the inferior Vertebrata. They are found in all the 
Myriapoda in the same segment, not only in the Scolopendra, but also, as we have 
already seen, in the Iulidce and Polydesmidce, and in the higher genera of the Chilo- 
poda Lithobius and Scutigera. In Scolopendra they pass a little forwards and out- 
wards before they bend downwards to surround the oesophagus at its junction with 
the cardiac extremity of the stomach, and unite beneath it to form the great supra- 
spinal artery. While passing round the oesophagus each of these arteries gives off on 
its front a large branch ( 5 ), which, as shown by Mr. Lord, is supplied to the muscles 
of the great mandibles, or foot-jaws (c). This branch, however, like the other 
systemic arteries, is divided into two ( s , t), one of which is given to the muscles of 
the foot-jaws, while the other passes into the first, or cephalic segment (a), and is 
distributed to the muscles of the pharynx and oesophagus, and anterior parts of the 
head. In S. alternans, Leach, there are two branches from each arch, the posterior 
of which is supplied to the salivary glands. In all the species there are minute 
branches given off from the great branch of the arch to the upper and under surface 
of the oesophagus and cardiac portion of the alimentary canal. The small median 
trunk (q), given off from the heart on the oesophagus with the lateral arches, passes 
forwards along the oesophagus to the cephalic segment, in which it gives off two pairs 
of minute secondary arches (u, v), and then, becoming very much smaller, the main 
trunk is divided behind the brain ( b ) into some minute ramifications, which are given 
to that organ, to the eyes ( d ), and to the antennse (a). The secondary arches give off a 
pair of branches to the maxillae and internal parts of the mouth, and then unite be- 
neath the oesophagus to form a small trunk (w) that passes backwards to the junc- 
tion of the great aortic arches with the supra-spinal artery. This junction of the 
arches beneath the oesophagus takes place immediately above the second suboeso- 
phageal ganglion, where the supra-spinal artery commences. 
The supra-spinal artery. — This vessel (fig. 22. a. w , x, y), which has become a 
matter of much interest in our examinations of the vascular system, both in Myria- 
poda and Arachnida, is extended along the middle line of the body, immediately 
above the nervous cords, as far as the terminal ganglion in the last segment. At its 
commencement it is nearly equal in size to the great nervous cords along which it 
