NERVOUS SYSTEM 165 



Turn the head and fix it with the right side upwards. 

 Remove the gena and mandible, and as much as is necessary 

 of the maxilla, suhm^ntum, and mentum, to expose the right 

 half of the following structwres. 



b. The para-cesophageal connectives are a pair of short 



thick bands of nervous tissue, running round the 

 sides of the oesophagus, from the lower part of 

 the supra-cesophageal gangha to the sub-oesopha- 

 geal ganglia. From each arises a nerve supplying 

 the labrum, as well as a nerve belonging to the 

 visceral system. 



c. The sub-oesophageal ganglia are a pair of large 



gangha lying between the submentum and the 

 oesophagus. Below they give off several nerves, 

 of which the two largest on each side supply the 

 maxillary and labial palps. Above, they give off 

 connectives, which run back through the neck 

 and form the anterior part of the ventral chain. 



2. The ventral chain. 



Fix the cockroach with the dorsal surface upwards : re- 

 move the gizzard, mesenteron, and proctodceum ; and twrn the 

 crop aside. 



The ventral chain consists of a double series of 

 gangha, with doable connectives, running along the 

 ventral wall of the body. 



A pair of closely apposed ganglia lies in each of 

 the three thoracic segments, and a pair of smaller 

 ganglia in each of the first six abdominal segments. 

 The last pair are the largest of the abdominal 

 ganglia, and give off nerves to the various parts of 

 the sixth and succeeding segments. 



3. The visceral nervous system arises as a pair of nerves, 



one from the anterior part of each para-oesophageal 

 connective. The two nerves unite in the frontal gan- 

 glion, a small median gangUon on the anterior wall 

 of the oesophagus, just below the antennary lobes. 



