STRUCTURE OF THE NERVE-CENTRES. 



579 



of animals possess striations more 

 or less regular. These, indeed, 

 were described soon after the cells 

 were discovered. While there is 

 no anatomist who denies the fact 

 that the substance of the cells is 

 marked by striae in many animals, 

 the existence of an analogous ar- 

 rangement in the human subject 

 is still doubtful. Some anatomists, 

 with Schultze, admit the striations 

 but have failed to connect them 

 with the nuclei and nucleoli. All 

 admit that they are demonstrated 

 with great difficulty; and, while 

 this question is so important that 

 it can hardly be neglected in study- 

 ing the physiological anatomy of 

 the nerve-centres, it is one con- 

 cerning which it seems impossible 

 to express a positive and definite 

 opinion. 



Connection of the Nerve-cells 

 with the Fibres and with each other. 

 Although the mode of connec- 

 tion of the nerve-cells with the 

 fibres and with each other is one 

 of the most important, in its physi- 

 ological bearings, of all the points 

 connected with the minute anat- 

 omy of the nerve-centres, it is im- 

 possible, in the present state of our 

 anatomical knowledge, to answer 

 the questions involved in a manner 

 entirely satisfactory. A full dis- 

 cussion of the different opinions 

 and the methods of investigation 

 that have been employed would 

 be out of place in this work. The 

 difficulties in the way of arriving 

 at positive information upon these 

 questions are the following : 



1. The nerve-cells and their 

 prolongations are so delicate and 

 easily torn that they cannot be 

 isolated and followed for any con- 

 siderable distance, and theoretical 

 considerations are constantly re- 

 quired to fill up the deficiencies 

 in actual observation. 



2. In the study of sections of 



the nerve-centres, the parts must be hardened and afterward rendered transparent by 



FIG. 184. Nerve- cell from the anterior cornua of the spinal cord 

 of the calf, maeeratedfor a short time in iodised serum ; mag- 

 nified 600 diameters. (Schultze.) 

 a, a, axis-cylinder prolongation; b, b, 5, 5, branching prolongations. 



