According to the textbook:

• Limbic system (A) is formed by the inner parts of cerebral hemispheres and associated deep structures like the Amygdala (III) and hippocampus .
• Arachnoid (B) is the very thin middle layer of the cranial meninges (IV) .
• Corpus callosum (C) is a tract of nerve fibres (II) that connects the two cerebral hemispheres .
• Hypothalamus (D) contains centres which control body temperature (I), urge for eating and drinking .