Spinal cord. Light micrograph (LM) of a transverse section through a mammalian thoracic spinal cord. The spinal cord has a central canal around which are the dorsal and ventral horns. These consist of grey matter, made up of neuron cell bodies and their connections (ganglia). Outside the grey matter is the white matter which consists mainly of long axons of the nerve cells (neurons) which run up and down the spinal cord.The outer membranes (meninges) protect and nourish the spinal cord. Magnification: x14 when printed at 10 centimetres across.