CHAPTER XIX. 



THE CENTRAL NERVOUS SYSTEM. 

 BY R W. AMIDON, M.D., NEW YOBK CITT. 



THE spinal dura mater is a serous membrane. Its structure 

 from without inward is : first, loose connective tissue ; then dense 

 fibrous tissue ; lastly, a layer of lymph-vessels and endothe- 

 lium. If one tears, with forceps, a shred from the outer surface 

 of the dura mater, fresh or hardened, stains with luematoxylon, 

 teases, and examines in glycerine, there is seen a loose network 

 of connective- tissue bundles containing free and fixed connec- 

 tive-tissue cells, blood-vessels, minute nerves, and some fat- 

 cells. This layer is continuous with the loose adipose tissue 

 which normally surrounds the dura mater. The denser tissue 

 next in order may be treated in the same way, and perhaps a 

 few spindle-shaped connective-tissue cells and elastic fibres 

 may be isolated. 



On transverse section, however (a very difficult thing to 

 make, by the way), the bulk of the membrane is seen to be a 

 dense mass, 0.5 1.0 mm. thick, composed of longitudinal and 

 horizontal connective-tissue bundles, interspersed here and 

 there with elastic fibres. In this layer blood-vessels and nerves 

 are very scanty and small. 



Next, immerse a piece of dura mater, as fresh as possible, 

 in a one per cent, solution of nitrate of silver. Leave it for sev- 

 eral hours, and then expose it for a few minutes to the sunlight. 

 When a brown tint is developed on the inner surface, remove 

 it, wash it in distilled water, and strip off the internal surface 

 with forceps. 



The shreds of tissue thus obtained show beautifully the 

 structure common to all serous membranes : first, a delicate en- 

 dothelial layer (see Fig. 125), consisting of flat, unequal, irreg- 

 ularly shaped cells, most of which are furnished with large, 



