n. the enlarged and highly developed mass of nervous tissue that forms the upper end of the *central nervous system (see illustration). The average adult human brain weighs about 1400 g (approximately 2% of total body weight) and is continuous below with the spinal cord. It is invested by three connective tissue membranes, the *meninges, and floats in *cerebrospinal fluid within the rigid casing formed by the bones of the skull. The brain is divided into the hindbrain (rhombencephalon), consisting of the *medulla oblongata, *pons, and *cerebellum; the *midbrain (mesencephalon); and the forebrain (prosencephalon), subdivided into the *cerebrum and the *diencephalon (including the *thalamus and *hypothalamus). The brain is usually considered to be the site of the working of the mind, but to what extent the concepts of ‘brain’ and ‘mind’ are interchangeable is a matter of debate and of concern to anyone facing brain surgery. Anatomical name: encephalon.... brain
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