228 ANNULATA. 
ing it. On contraction of the heart the blood is driven 
forwards along the dorsal aorta, which terminates near 
the brain in a funnel opening into the body-cavity. The 
body-cavity is, therefore, a blood-space or heemoccele in 
which the blood bathes all the tissues and eventually finds 
its way back to the heart. Immediately under the heart 
the pericardial septum stretches across the body-cavity, 
partially dividing it into a dorsal pericardial sinus and a 
ventral main cavity. The septum is a fenestrated mem- 
brane, being perforated by numerous apertures. 
Fig. 151.—TRANSVERSE SECTION OF BLATTA, 
(Semi-diagram matic. ) 
Heart. 
Dorsal Branch of Dorsal Muscles. 
Trachea. Alary Muscles. 
Tergon. /, Pericardial 
“a Septum. 
ventral Muscle. 
Gizzard with 
Sternon. Teeth. 
Ventral 
Muscles. . Hepatic Caca. 
Nerve-cord. “ Body-cavity (a blood-space). 
Passing through the anterior portion of the abdonien. 
The brain lies in the head dorsal to the cesophagus. It 
has a paired anterior lobe which supplies the 
eyes and a posterior giving nerves to the an- 
tenne. A ring round the cesophagus is completed by a’sub- 
cesophageal mass, composed of three pairs of fused ganglia, 
belonging to the mandibular, maxillary and labial segments. 
This is followed by a double ventral nerve-chain with three 
thoracic ganglia and six abdominal. 
Nervous. 
The cockroach has a nervous system much like that of the lobster. 
As in the latter, we can recognise certain fusions. If we start with a 
brain and a chain with ganglia to each segment we get a total of 
five cephalic (of which the second has no appendages), three thoracic 
and ten abdominal ganglia, or eighteen in all. These are reduced to 
ten by the fusion of the first two to the brain, the fusion of the next 
