Methods for counting neurons

The invention provides a seal for pipe joint couplings, the present seal comprising a sleeve member receivable over the pipe joint and extending for a relatively short distance along each of the pipes. The seal further comprises an annular pressure chamber formed in the inner wall of the sleeve facing each of the pipes, the outer surface of each pipe acting to define the chamber, each pressure chamber being partially positioned into two sub-chambers by an inwardly extending annular bead formed on the sleeve, the sub-chambers each having packings such as O-rings disposed therein.