Medulla oblongata again, but note the structure opening up on the dorsal side. Instead of the central canal we see the fourth ventricle, though not really broad yet.

The key to the section is in the regions labelled 'A' and 'B'.

'A' is a nucleus with a characteristic crumpled-bag appearance, and fibres are seen emerging from its open centre on the medial side.

Note the direction of the fibre bundles at 'B'. Notice that the ventral ends of these bundles seem to come from the opposite olive.

What else would you expect at this level? (Remember, a lot of it will not be distinguishable in the photograph!)

Some answers, some more questions...