174 THE COCKROACH. 



Bemove the clypeus and the anterior portion of" the epi- 

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

 not to injure the ganglia, luhich lie close beneath the cly- 

 peus. 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 ivith the right side uppermost. 

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

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

 following structures on the right side. 



b. The para-oesophageal 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- oesophageal 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-oesophageal 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 . 



