It is important to cut off meninges overlying the brain, particularly where it dips between cerebrum and cerebellum. If this is not done, you will rip the front part of the brain from the posterior half as you attempt to remove it. Cut the meninges over the medulla along the dorsal midline. If it is necessary to sample the brain further for microbiology, do it now before you take the brain out. You do not need to submit half a brain for microbiology.
Microbiologists require small pieces of tissue for culture.
The pathologist on the other hand needs an intact or nearly intact brain. The sort of handling a brain gets if split longitudinally introduces considerable artifact. One of the few times when it is necessary to cut a brain in half is if organophosphate poisoning is suspected, since half the brain is required for cholinesterase activity. If you suspect an ascending infection, including rabies, and cannot send an intact head, please make sure you submit unfixed the most caudal portion of medulla oblongata. This may be the only place where antigen is present.