370 KARM NARAYAN BAHL 
absent ; it bifurcates in the fourteenth segment, and the two 
branches curve round (fig. 5) the nerve-cord to be continued 
into the two lateral oesophageal vessels. A new large vessel 
in this region limited in extent is the supra-intestinal vessel, 
which is closely attached to the oesophagus in the mid-dorsal 
lme and communicates freely with the blood-plexus of the 
oesophagus. Besides these there are the big pulsating ‘ hearts ’ 
in many of the segments of this region, by means of which the 
dorsal vessel pumps out all the blood it receives either into the 
ventral vessel to be distributed by it or directly to the various 
organs in this part of the body. 
(a) The Longitudinal Trunks. 
1. The Dorsal Vessel.—The dorsal vessel continues 
in front up to the third segment, where it divides into three 
branches near the cerebral ganglion, these branches being 
distributed over the pharyngeal mass and the wall of the 
bueceal cavity. While in the region of the intestine the dorsal 
vessel lies close upon the gut, bemg connected with it by two 
pairs of dorso-intestinals ; in this anterior region it is removed 
considerably away from the oesophagus. Except in the four- 
teenth segment, where the dorsal vessel is connected by a single 
(not two) pair of dorso-intestinals, there are no such venous 
branches at all in the anterior cephalized region. Since there 
is no subneural vessel in this region the commissural vessels 
connecting the dorsal with the subneural in the intestinal 
region are absent in this anterior region. However, the dorsal 
vessel here gives off, in many segments, pulsatile vessels called 
the ‘hearts’. ‘These structures [shall describeseparately below. 
The intersegmental valves present in the posterior part of 
the dorsal vessel are present here also, and have the same 
structure and disposition, making the blood flow in the anterior 
direction. But the valves at the orifices of the dorso-intestinals 
and commissurals into the dorsal (vide infra) in the posterior 
region have no counterpart here ; in their place there are other 
valves away from these orifices, leading the blood outwards 
from the dorsal vessel. 
