182 THE COCKROACH. 



Remove the clypeus and the anterior portion of the epi- 

 cranium with scissors or the point of a scalpel, taking care 

 not to injure the ganglia, which lie close beneath the clypeus. 

 Carefully expose and clean the following structures, avoiding 

 injury to the cephalic portion of the visceral nervous system : 



a. The supra-oesophageal, or ' cerebral,' ganglia are 



a pair of large closely apposed ganglia close to 

 the anterior surface of the head. They are sup- 

 ported by an internal chitinous framework, the 

 tentorium. 



i. The * hemispheres ' are the large rounded upper 

 parts of the ganglia. From them arise the 

 large optic nerves. 



ii. The antennary lobes are the smaller and lower 

 portions of the ganglia. From them the an- 

 tennary nerves arise. 



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

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

 of the first maxilla, submentum, and mentum, to expose the 

 following structures on the right side : 



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 ganglia to the sub-cesopha- 

 geal ganglia. From each a nerve arises supplying 

 the labrum, as well as a nerve belonging to the 

 visceral system. 



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



ganglia 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. 



