THE SPINAL CORD 21 



Plates III. to VIII. show the large cells of the gray matter of the spinal cord both in 

 transverse and in longitudinal section. These cells are of various shapes with numerous 

 branches. They measure from 70 to 130/^1. There are long narrow cells whose branches 

 have two principal directions, as shown in Plate III. There are oval or polygonal cells with 

 branches running in many directions, as shown in Plates IV. to VIII. In all these cells it 

 is possible to distinguish a large body, which by other methods of staining can be shown to 

 contain a nucleus and nucleolus, and two varieties of branches characteristic of all nerve 

 cells ; viz. : dendrites and neuraxons. 



THE DENDRITES are branches which come off from projections of the body of the cell. 

 They are thick near the cell, but diminish in size as they pass outward. They present 

 numerous offshoots in their course, branching like the limbs of a tree. The size of the dendrite 

 varies in its course, and it may present a varicose appearance. The surface of the dendrite is 

 not smooth, but presents a fine moss-like or furry appearance. The dendrites and their branches 

 terminate in free ends which usually have a little knob-like swelling upon them. Some of the 

 dendrites are very long. Others are quite short and terminate near to the cell. The dendrites 

 are made up of protoplasm similar to the cell body, and hence were formerly called protoplasmic 

 processes. It has been thought by almost all authorities ( Ramon y Cajal, 1 Van Gehuchten, 2 

 Lenhossek) that they collect the impulses going to the cell, from the fine neuraxons of other 

 cells, whose terminals reach the gray matter, and hence are cellulipetal in function. This is the 

 view generally accepted. It has been thought by Golgi that they have a purely nutritive function 

 and play no part in the action of the cell, being in relation with the blood-vessels at their 

 extremities and thus collecting nutrient substances for the cell, just as the roots of a tree 

 nourish its trunk. This view has, however, not met with any general acceptance, for Lenhossek 

 has shown that the dendrites develop long before the blood-vessels, and do not depend upon 

 these latter for their direction or distribution. It was formerly believed that after many branch- 

 ings the dendrites of one cell united with those of other cells, forming thus a network of fine 

 fibres throughout the gray matter (Gerlach). Golgi refuted this theory, and it is now 

 known that no such network exists ; and that while the dendrites may interlace and probably 

 touch one another, as do the adjacent leaves and branches of the trees in a forest, they never 

 really join one another, and are thus as independent of each other as are the trees. Thus 

 each nerve cell with its dendrites must be considered as a separate entity. 



The cells, however, are in a close functional relation with one another though not joined 



!S. R. Cayal, Les Nouvelles Ide"es sur la Structure du Systeme Nerveux. Paris, 1894. Also Internationale Monatschrift 

 f. Anat. u. Phys. Bd. VI., VII., VIII., and La Cellule, Tome VII. and IX. 

 2 Van Gehuchten, Le Systtme Nerveux de 1'Homme. Lierre, 1893. 



