Yes, I was indicating that with a limited 1ma current an h bridge driver is simple.
constant-current-hbridge.fzz (9.9 KB)
a circuit like this should work (you would be best to collaborate with a real electrical engineer to get the circuit right though!) The Arduino drives the inputs to the driver (which needs to translate the logic levels to ~70V for the high side of the h bridge) a standard hbridge driver IC would work as well. Essentially the two states are Q1 off Q2 on Q3 on Q4 off which puts electrode1 at ground and Electorde2 at ~70V. Reversing the state to Q1on Q2 off Q3 off Q4 on reverses the polarity. The constant current on the 70V means the usual problem of both Q1 and Q2 being on at the same time causing a short isn’t important. The 1ma current limit on the CC supply makes that a non issue. All that said I assume you are aware the there are commercial versions of this device available (I don’t know if they have constant current outputs or not as there isn’t much technical information available.) I have made Fritzing parts for a number of them I think at least one with 4 probes. Here is a recently modified 3 probe version
Peter