Final answer:
The corpus callosum is a thick bundle of axons that connects the left and right hemispheres of the brain, while the septum pellucidum is a thin membrane that separates the lateral ventricles. The fornix is another midline structure adjacent to the corpus callosum and septum pellucidum.
Step-by-step explanation:
The corpus callosum is a thick bundle of axons that connects the left and right hemispheres of the brain, allowing for communication and information sharing between the two sides. It is located deep within the brain, beneath the cerebral cortex.
On the other hand, the septum pellucidum is a thin membrane that separates the lateral ventricles of the brain.Another midline structure that is immediately adjacent to the corpus callosum and septum pellucidum is the fornix. The fornix is a C-shaped bundle of fibers that connects the hippocampus to other parts of the brain.