SECT. 125.] NERVOUS SYSTEM. 257 



Quite recently Iicmah (l.c.) has given an entirely new exposition of the 

 course of the fibres in the sympathetic, which is based upon the discovery 

 made by him in 1837 of multipolar cells in sympathetic ganglia. According 

 to Iiemak, the upper branch of each ramus eommunicans, which he calls 

 spinalis, conducts to the sympathetic, fibres of the motor and sensitive roots 

 of the spinal nerves, which, in the nearest ganglion, or in the subsequent one, 

 become connected with the multipolar cells of the latter. From these same 

 cells there then arise thicker and finer, dark-bordered, and also non-medul- 

 late.l fibres, which, partly by means of the lower branch of the ramus eom- 

 municans, or the ramiis eommunicans sympatheticus, join the spinal nerves to be 

 distributed in the periphery, partly pass into the peripheral ramifications of 

 the sympathetic itself, in which they become again connected (once or several 

 times, according to the number of the peripheral ganglia), with multipolar 

 cells, which on their part, give off, as might be expected, peripheral branches. 

 According to this view, the sympathetic, therefore, contains no spinal nerve- 

 fibres merely running along its trunk and branches and not uniting with its 

 elements, and no fibres of its own running independently, but appears as an 

 aggregate of many spinal nerves, whose elements are variously divided, and 

 contain ganglionic cells at the places of division. By means of these cells, 

 and the numerous tubes passing from them to the periphery, the inde- 

 pendence of the sympathetic would be established and the increase of fibres 

 accounted for ; and doubtless, also, physiological explanations would be found 

 to answer better than according to the hitherto received views of the struc- 

 ture of the sympathetic ; only it is to be regretted that Remak has forgotten 

 to adduce the proofs of his hypothesis, here shortly sketched, for the par- 

 ticulars of which my Handbook may be consulted, 2nd Edit. p. 3 54. 



Development of the Elements of the Nervous System. 



§ 125. The nerve-cells, wherever they occur, result merely from 

 metamorphosis of the so-called embryonic cells; some simply 

 enlarging, others growing out into a variable number of processes, 

 and, in part at least, becoming connected with the nerve-fibres. 

 Many nerve-cells appear at a later period to multiply by division; 

 at least, I cannot otherwise explain the frequent occurrence of two 

 nuclei in the nerve-cells of young animals, especially in the ganglia, 

 and of cells connected by filaments of communication, which have 

 been seen by different observers. 



The peripheral nerve-tubes arise in the place which they are 

 destined to occupy, but are further developed in such a manner, 

 that the central ends are always more advanced in formation than 

 the peripheral. With the exception of the nerve-terminations, the 

 nerve-tubes are developed from fusiform nucleated cells, which are 

 merely modifications of the primitive formative cells of the embryo, 

 and which become connected to form pale, flat, long, nucleated 

 tubes or fibres, 0001'" to 0003'" in breadth. The nerves at first 



s 



