Look at Figure 29.23 p. 489. Brain Cavities and Canals. It is also where most of the cerebrospinal fluid is made. Brain cells are not bathed in normal interstitial fluid as are the cells of the rest of the body. They are bathed in either cerebrospinal fluid or are separated by a covering of glial cells.
Cerebrospinal fluid is very nearly a pure sodium chloride solution.
It is very simple. Memory is divided into two mechanisms. Short-term memory lasts for a few seconds to a few hours. It is composed of a network of activated cells that keep bouncing the information through the same circuitry. If interrupted, long-term memory will not form.