XXX.] SPINAL CORD. 329 



missure, composed anteriorly of white fibres crossing from one side 

 of the cord to the other white commissure ; and posteriorly of 

 grey matter posterior commissure. In the middle of the latter 

 is the minute central canal, lined by columnar ciliated epithelium. 

 In each half of the cord is a crescent-shaped mass of grey matter 

 as seen in transverse section, the two masses connected across the 

 middle line, and presenting more or less the form of an H, with the 

 extremities of its vertical limbs turned outwards. Its extremities 

 are the anterior and posterior cornua. The anterior cornua are 

 generally wider and shorter than the posterior, which are narrow, 

 and come nearer the surface of the cord. The nerve-roots arise 

 from the cornua, the anterior root by several bundles from the 

 anterior cornu, and the posterior root by a single bundle from the 

 posterior one. In this way, and by the existence of the fissures, 

 each half of the white matter of the cord may be conveniently 

 described as divided into an anterior, lateral, and posterior 

 column, or more correctly into an antero-lateral and a posterior. 

 The anterior cornu contains numerous large multipolar nerve-cells 

 arranged in groups. Each cell is continuous, through its axis- 

 cylinder process, with a nerve-fibre. The arrangement and number 

 of cells, however, vary in different parts of the cord. There are no 

 large nerve-cells only small fusiform ones and some small isolated 

 or " solitary " cells in the posterior cornu, which is capped by a 

 peculiar greyish matter the substantia gelatinosa of Rolando. 

 The white matter is composed of medullated nerve-fibres small 

 and large arranged for the most part longitudinally, so that in a 

 transverse section, when stained with carmine, they appear like 

 clear rings with a central, red-stained spot the axis-cylinder. In 

 Pal's method the myelin is stained, and so they appear as blackish 

 circles with a clear centre. The nerve-fibres, and grey matter as 

 well, arc supported by a peculiar sustentacular tissue neuroglia 

 composed of glia-cells (p. 343), and both are supplied by blood- 

 vessels, the grey matter, however, being far more vascular than the 

 white. The grey matter, besides blood-vessels, lymphatics, glia-cells, 

 nerve-cells, and their numerous processes, also contains nerve-fibres. 



The nerve-cells vary in size, shape, and other characters in the 

 different parts of the cord. Golgi speaks of two types of nerve-cells 

 in the spinal cord. 



Type i, or Motor Type, corresponding to the multipolar cells of the 

 anterior cornu. In these one process retains its individuality, and 

 passes directly to become an axis-cylinder of a medullated motor 

 nerve-fibre in the anterior root. This axis-cylinder process gives off 

 a few secondary lateral processes or collaterals, which divide and 

 enter into the formation of the nerve-complex in the grey matter. 

 The protoplasmic processes subdivide, and also form part of the 



