Grey Matter

Grey MatterIf a thin transverse section of the spinal cord be examined under the microscope it will be seen that the central grey material assumes roughly the form of the letter H. The transverse bar contains the central canal, and serves to connect the parallel limbs to one another; it is known as the grey commissure.

In each of the lateral limbs an anterior and a posterior part are recognised. The anterior portion, which, is somewhat bulbous in shape, is termed the anterior cornu or horn: the axons of the majority of its cells are the nerve fibres forming the anterior or motor root of the spinal nerve; from other groups of cells the efferent sympathetic fibres emerge (Fig. 36).

The posterior portion, called the posterior cornu or horn, tapers towards its extremity which is near the periphery of the cord; the cells which it contains have, for the most part, short axons which arborise round the anterior horn cells of its own or of the opposite side, either in its own or in neigh bouring segments.

A special group of nerve cells situated at the base of the posterior horn differs from these in possessing long axons which run into the white matter and thence towards the brain, in a manner to be presently described. This collection of cells forms a long column known as the column of Lockhart Clarke.