How to apply current and measure voltage between electrodes.

Hello all,

I am an Arduino newbie working on a project where I have 4 electrodes (let's say a,b,c,d). I have to apply a small current (~10mA) between two electrodes (Copper strips soldered to jumper cables) a,b and measure the voltage between c,d. All the electrodes are placed in an electrolyte. I have an Arduino Mega. What is the best way to perform this?
I know we can measure voltage using analog pins. How can I apply the current between electrodes?

Please guide me to a forum post if it has been discussed previously.

Thank you.

You might find previous projects if you Google "wenner array".

Thank you so much for the reply. I found this circuit with connections and I have a small question regarding this circuit. My electrodes are copper bars inserted in saline solution. So I assume the current will flow freely between A and B.

Does it mean I am shorting the Arduino?
If so what precautions should I take to avoid it?

If I am not shorting the circuit, Can I insert the electrodes into saline solution and perform the experiment?
and How can I control the current passing through the circuits? For example (10mA,20mA,30mA and 40 mA)

Be aware that passing a DC current through electrodes in a saline solution will quickly deplete one of the electrodes