ABSTRACT
In the last chapter I said that the nerve fibre or axon is covered by an insulating coat (myelin) and a nerve must have its myelin sheath before it can begin to conduct an impulse. The importance of this myelin can be seen in those unfortunate patients with multiple sclerosis, a condition in which the myelin begins to disintegrate. At birth the part of the brain cortex which controls physical movement (motor cortex) and a special part of the brain (the pyramidal tract) containing the nerve fibres which carry instructions from the level of the cortex to the motor nerves are not ready for action because the fibres are not myelinated. A few months after birth myelin has begun to be laid down in the tracts.
