The nervous system in the thorax (Plate 10)

1. Remove the oesophagus and salivary glands with forceps.

2. Observe:

   2.1. the combined furcae of T2 and T3, which are now conspicuous.

   They form a strong strut and bridge across the thorax and protect:

   2.2. the great second ganglion, which can be seen below the furcae;

   2.3. the first ganglion lies in front of and partly concealed by the furca of T1, at the anterior end of the thorax. To see this, it will probably be necessary to remove more of the body wall in this region. Both ganglia can be exposed by removing the overlying parts of the furcae, using the point of the knife and forceps. Sheets of semi-transparent muscles attached to the furca will also have to be removed; this must be done cautiously, for the ganglia are very easily damaged. Notice the thick twin commissures joining the ganglia;

   2.4. commissures also run forward from the first ganglion to the suboesophageal in the head, and from the second ganglion to the abdomen, where they join the abdominal chain;

   2.5. nerves from the second ganglion can also be seen passing to the propodeum and into the abdomen, where they serve A2.