Access to the parasitology-mycology labs (3rd floor) is exclusively through the front of B43a.
After entering the building, climb up the stairs to the third floor, then turn right until the end of the corridor. The lab is on the left hand side, coming from the staircase.
A specific room is dedicated to Mycology (room 3/75c): it is located at the back of the lab, on the left.
