140 NERVOUS TISSUE. 



In the spinal ganglia of man the cells commonly appear to possess but a single 

 process, which runs peripherally ; on the other hand, multipolar cells are occa- 

 sionally found. The latter, according to Max Schultze, are also to be met with 

 in the sjTnpathetic ganglia (see iig. 93), 



OF THE CEEEBRO-SPINAL NERVES. 



Construction. — These nerves are formed of the nerve-fibres 

 ah-eady described, collected together and bound up in sheaths of 

 connective tissue. A larger or smaller number of fibres inclosed 

 in a tubular sheath form a slender round cord of no determinate 

 size, usually named a. ftimculiis; if a nerve be very small it may 

 consist of but one such cord, but in larger nerves several funiculi 

 are united together into one or more bundles, which, being wrapped 

 up in a common membranous covering, constitute the nerve (fig. 97). 

 Accordingly, in dissecting a nerve, we first come to an outward 

 covering, formed of connective tissue, often so strong and dense 

 that it might well be called fibrous. From this common sheath we 

 trace laminte passing inwards between the larger and smaller bundles 

 of funiculi, and finally between the funiculi themselves, connecting 



them together as well as con- 

 Fig. 97. ducting and supporting the 

 fine blood-vessels which are 

 distributed to the nerve. 

 But, besides the interposed 

 areolar tissue which connects 

 these smallest cords, each 

 Fig. 97.-PORTION OF T^Zl^^K OP A Nerve funiculus has a special sheath 



CONSISTING OF MANY SMALLER CoRDS OR FUNICULI 01 itS OWH, aS Will DC mi- 



WRAPPED UP IN A COMMON Sheatii. mediately noticed. 



A, the nerve ; b, a single funiculus drawn out The COmmon sheatll and 



from the rest (from Sir C. Bell). its subdivisions COUsist of 



connective tissue, presenting 

 the usual white and yellow constituent fibres of that texture, the 

 latter being present in considerable proportion : frequently also a 

 little fat is to be found. The special sheaths of the funiculi, 

 on the other hand, appear to be formed essentially of a fine trans- 

 parent membrane, which may without difficulty be stripped off, in 

 form of a tube, from the little bundle of nerve-fibres of which the 

 funiculus consists. AVhen examined with a high power of the micro- 

 scope, this membrane presents the aspect of a thin transparent film, 

 which in some parts appears to be quite simple and homogeneous, but 

 is more generally marked with extremely fine retioiulated fibres. Cor- 

 puscles resembling elongated cell-nuclei may be seen upon it when 

 acetic acid is applied, and by treatment with nitrate of silver it 

 may be shown that the film above mentioned is not in reality simple, 

 but is made up of two, three, or more excessively delicate lamella?, on 

 the surface of which an epithelioid layer of extremely fine flattened 

 cells, to which the nuclei above mentioned belong, may occasionally 

 be observed. The fine reticulated fibres seen on the lamellae are 

 jjrobably of an elastic nature ; in some parts they appear merely as a 

 series of granules, as if incompletely developed (seep. 71). Moreover, 

 small plates of elastic substance are here and there met with in the 

 lamella3 which also appear granulated near their edges (Rauvier). 



