The subarachanoid space lies between the arachnoid and pia mater. It is filled with cerebrospinal fluid. All blood vessels entering the brain, as well as cranial nerves pass through this space. The term arachnoid refers to the spider web like appearance of the blood vessels within the space.
Why do biologists organize living things into groups? What do the levels of classification indicate about the relationship between organisms? What characteristics are used to classify organisms into domains and kingdoms? What is the scientific study of how living things are classified called? Taxonomy
Technically, science means the systematic study of the structure and behavior of the physical and natural world. Political science attempts to claim the rubric of science because of its systematic study of politics (as opposed to the physical and natural world; i.e., the modifier political.).