Figure 3.1 Filling Chamber. Build a wall of Vaseline in a Petri dish cover and put saline on both sides of it. Lay the isolated ganglia and nerve in the saline on one side and pull the nerve over the central wall. Add another layer of Vaseline over the nerve and cut the end of the nerve. Replace the saline on the nerve side with cobalt chloride solution. Cover with the Petri dish bottom and refrigerate overnight.