clviii NERVOUS SYSTEM. 



origin to its entrance into the internal auditory foramen, where it becomes fascicu- 

 lated ; also of the intracranial part of the olfactory, which, however, contains in addi- 

 tion grey matter and nerve-cells, and may, indeed, be reckoned as part of the brain. 

 The branches of the olfactory in the nose are almost wholly made up of fibres bearing 

 nuclei, and having all the outward characters of the grey fibres, like which, also, they 

 cohere or cling fast together in the bundles which they form. Some branches seem 

 to consist entirely of such fibres ; others contain a few white fibres intermixed, which, 

 however, may be derived from the nasal branches of the fifth pair. 



OF THE SYMPATHETIC OB GANGLIONIC NERVE. 



This name is commonly applied to a nerve or system of nerves present on 

 both sides of the body, and consisting of the following parts, viz. 1. A 

 series of ganglia, placed along the spinal column by the side of the vertebrae, 

 connected with each other by an intermediate nerve-cord, and extending 

 upwards to the base of the skull and downwards as far as the coccyx. This 

 principal chain of ganglia, with the cord connecting them, forms what is 

 often named the trunk of the sympathetic. 2. Communicating branches, 

 which connect these ganglia or the intermediate cord with all the spinal and 

 several of the cranial nerves. 3. Primary branches passing off from the 

 ganglionic chain or trunk of the nerve, and either bestowing themselves at 

 once, and generally in form of plexuses, on the neighbouring blood-vessels, 

 glands, and other organs, or, as is the case with the greater number, pro- 

 ceeding in the first instance to other ganglia of greater or less size (some- 

 times named prevertebral) situated in the thorax, abdomen, and pelvis, 

 and usually collected into groups or coalescing into larger gaugl ionic masses 

 near the roots of the great arteries of the viscera. 4. Numerous plexuses 

 of nerves, sent off from these visceral or prsevertebral ganglia to the viscera, 

 usually creeping along the branches of arteries, and containing in various 

 parts little ganglia disseminated among them. Some of these plexuses also 

 receive contributions from spinal or cerebral nerves, by means of branches 

 which immediately proceed to them without previously joining the main 

 series of ganglia. 



Structure of the sympathetic nerve. The nervous cords of the sympathetic 

 consist of white fibres, and of pale or grey fibres mixed with, a greater or 

 less amount of filamentous connective tissue, and inclosed in a common ex- 

 ternal fibro-areolar sheath. The white fibres differ greatly from each other 

 in thickness. A few are of large size, ranging from - ^^ to -jj^-^ of an 

 inch : but the greater number are of much smaller dimensions, measuring 

 from about 8 Vo o" to i^VtT ^ an * uc h * n diameter, and, though having a 

 well-defined sharp outline, for the most part fail to present the distinct 

 double contour seen in the larger and more typical examples of the tubular 

 fibre. The pale, non-medullated fibres, have partly the characters of 

 Remak's grey fibres, already described, and often look as if they were really 

 made up of exquisitely fine fibrils ; but there are also pale fibres of much 

 less thickness, which, at t-hort distances, are interrupted by, or might be 

 said to swell out into, fusiform nuclei. 



The more grey-looking branches or bundles of the sympathetic consist of 

 a large number of the pale fibres mixed with a few of the dark-bordered 

 kind : the whiter cords, on the other hand, contain a proportionally large 

 amount of white fibres, and fewer of the grey ; and in some parts of the 

 nerve grey fasciculi and white fasciculi, respectively constituted as above 

 described, run alongside of each other in the same cords for a considerable 

 space without mixing. This arrangement may be seen in some of the 

 branches of communication with the spinal nerves, in the trunk or cord 



