SYMPATHETIC NERVE. 



tinctly tubular character also ; in those of the 

 3rd, 4th, and 7th, the double contour is more 



Fig. 301. 



From the Gassericm ganyUon of the same animal as 

 the preceding figure. 



a, portion of ganglion with corpuscles in situ ; 

 I, three corpuscles included within a single capsule; 



c, ganglionic corpuscles freed from their capsules ; 



d, nerve-tubes connected with the ganglion. 



or less distinctly visible. The optic nerve con- 

 sists of fine tubular fibres mingled with small 

 round or oval bodies. The nerve-fibres in the 

 brachial plexus also present the character of 

 perfect tubular fibres ; they are narrower than 

 in the adult animal. So also the fibres in the 

 trunk of the pneumogastric ; throughout the 

 entire extent of the trunk of this nerve, in 

 the neck and upper part of the thorax, there 

 were embedded amongst its fibres ganglionic 

 corpuscles similar in their character to those 

 occurring in the ganglia of the cerebro-spinal 

 nerves. Sometimes a single corpuscle lay 

 imbedded in a bundle of nerve- fibres ; in other 

 parts two were seen, one situated above the 

 other ; and in some parts there were as many 

 as six, all arranged close together in linear 

 series ; some of them were seen to give off a 

 nerve-tube at one extremity ; and once or 

 twice the corpuscle was seen to be connected 

 with two such, one passing towards the 

 centre, the other in the direction of the peri- 

 phery. 



The main cord of the sympathetic appears 

 to be entirely composed of fibres presenting 



the nuclear character, similar to those already 

 described in connection with its ganglia, and 

 representing an early stage of the development 

 of the cerebro-spinal nerve-fibres. Addition 

 of dilute solution of soda brings into view 

 a few tubular nerve-fibres similar to those in 

 the spinal nerves. The splanchnic nerves 

 present the same structure as the cord of the 

 sympathetic, containing a few tubular nerve- 

 fibre.";, but being chiefly composed of the other 

 structures. In one of the nerve-filaments from 

 the surface of the right ventricle of the heart, 



nerve fibres from the brachial plexus of a Calf 

 18 inches long. B. a, nerve-fibres from the sympa- 

 thetic cord in the thorax; b, the same treated with 

 dilute solution of soda, showing the presence of 

 tubular nerve-fibres, 1 1, similar to those in the 

 cerebro-spiual nerves. 



there were no tubular nerve-fibres present ; it 

 consisted entirely of structures similar to those 

 already described. As regards the communi- 

 cating branches, all of them contained more 

 or fewer tubular nerve-fibres ; some appeared 

 to be entirely composed of these, while others 

 consisted chiefly of the partially-developed 

 nerve-fibres. The difference in point of struc- 

 ture between the fibres in the cerebro-spinal 

 nerves and those occurring in the sympathetic 

 is at this period of embryonic life very re- 

 markable : while the former present for the 

 most part the tubular character of the per- 

 fectly-formed nerve-tube, the latter appear to 

 consist of a mass of blastema with numerous 

 granular nuclei imbedded in it, corresponding, 

 in short, to the fibres of the cerebro-spinal 

 system in the fcetus measuring 6 to 8 inches 

 in length. This also applies, though perhaps 

 in a less degree, to the ganglia of the sympa- 

 thetic as compared with those on the cerebro- 

 spinal nerves, the latter being more fully 

 developed, both as regards their ganglionic 

 corpuscles and nerve-fibres, than the former. 



As regards the further development of the 

 nerve-fibres of the sympathetic, it would ap- 

 pear, from the observations of Volkmann and 

 Bidder, that they undergo little further change 

 during the whole period of embryonic life. 



