The Brain:
Brain and cranial nerves are the chief parts of the whole nervous system. It is a mass of nervous tissues made up of soft grey and white matter. It occupies the whole of cranium. Cranium is like the iron safe to keep up the treasure ‘brain’. It is surrounded by three membranes or Meninges, viz., (1) dura mater, the fibrous connective tissue by the side of the cranial bones; (2) pia mater, the connective tissue containing a network of blood vessels, which penetrates and nourishes all the parts of the brain; and (3) arachnoid, a very fine membrane around the brain. Below the arachnoid there is the space which contains the cerebro-spinal fluid that is intended to prevent any injury to the brain. The brain looks as if it is floating on this liquid.
The brain can be divided into two halves, right and left hemispheres, by a central Sulcus or tissue. There are several lobes or smaller portions in the brain such as the parietal and temporal lobes on the sides, the occipital lobe at the posterior portion of cerebellum, etc. There are many convolutions or Gyre in every lobe. Again, for the sake of study, we can divide the brain into four sections.
1. Cerebrum: It is the anterior, oval-shaped larger part of the brain. It is situated in the upper portion of the cranial cavity. This contains the important centres of hearing, speech, sight, etc. The pineal gland which is regarded as the seat of the soul and which plays a prominent part in Samadhi and psychic phenomena is situated here.
2. Cerebellum, the little or hind brain: This is the main portion of the brain, oblong-shaped, situated just above the fourth ventricle and below and behind the brain. Here the grey matter is arranged over the white matter. It regulates the muscular co-ordination. Mind rests here during dreams.
