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SECT. Iig.] 



 



NERVOUS SYSTEM. 



245 



to be examined after they have been teased out, or in the ,latura l state, with 

 the aid of acetic acid, but especially of diluted caustic soil;. The chief 

 constituents of the ganglia, the ganglionic //lobules, or ganglionic cti'ti^S- I0I )» 

 possess a distinct external covering, are roundish, elongated or pear-sfll )e d, 

 and measure from o - oia'" to o - o+'" in diameter, the majority being o - o2'" aim 

 o - o3'". The contents of these are throughout finely granular, and not unfre- 

 quently in the neighbourhood of the nucleus, there is a collection of yellow, or 

 yellowish brown, pigment granules, which are more numerous the older the 

 cell is, and to which the yellow colour of the ganglia is mainly owing. These 

 ganglionic cells are found in larger quantities at the surface of the ganglia 

 between the neurilemma and the root-fibres ; and, at least in man, also in the 

 interior of the ganglia, where, collected in heaps, they fill up the meshes 

 between the plexuses of nerve-tubes. The individual cells are maintained in 

 their position and separated from the surrounding parts and from the nerve- 

 tubes, by a special tissue, which, when the cells are isolated, appears as a 

 special covering to each, and has, accordingly, been called the outer sheath ; 

 but it, in fact, forms a system of variously connected small partitions tra- 

 versing the whole ganglion, and enclosing the several cells." This interme- 

 diate substance is obviously referable to connective tissue, and occurs in 

 form of a sometimes more homogeneous, sometimes more fibrous matter, with 

 interspersed flat, roundish nuclei of o - oo2'" to o'oo3'" in diameter; or in form 

 of separate, elongated, triangular or fusiform cells, which correspond to the 

 formative cells of the connective or of the elastic tissue. 



In man, and in the mammalia, pale processes of o - ooi5'" to 0-0025'" in 

 diameter proceed from by far the most of the ganglionic cells ; these exactly 

 correspond to those of the central cells, are Fig. 101 



provided, however, with a special covering, and, 

 as I discovered in 1844, each becomes continued 

 into a dark bordered nerve-tube (fig. 101). 

 The cells are mostly furnished with only one 

 process, and are then called unipolar; yet in 

 man and in mammalia, cells with two pale pro- 

 cesses, which pass into two nerve-fibres, also 

 occur, the so-called "bipolar cells. Whether there 

 be one or two fibres coming from a cell, they 

 always proceed towards the periphery ; at least 

 in investigating very small ganglia only such 

 fibres are seen, and Stannitts also found, that in 

 the bipolar cells of the calf, the two processes 

 lay close together. It is difficult to determine 

 whether cells without processes also occur in 

 spinal ganglia, since the processes readily break 

 off, and mutilated cells are very apt to be taken 

 for apolar cells. The dark-bordered fibres arising 

 from the ganglionic ceils, simply form the con- 

 tinuations of the pale processes of the cells, the 

 .coverings and contents of both parts passing 

 continuously in each other, so that the membrane 

 and the contents of a cell are connected with 

 the sheath of a nerve-tube, and with the medullary sheath, together 



Branch of the human ner- 

 vus coceygeus within the dura 



mater, with an attached pedun- 

 cated ganglion-globule in its 

 nucleated sheath, in which the 

 conmencement of the fibre is 

 very evident. Magnified 350 

 times. 



