454 SPECIAL HISTOLOGY. 



venous sinuses, which are simple excavations in it, for the con- 

 veyance of blood and lined with an epithelium ; and most of 

 which are obviously situated between the periosteal lamella and 

 the proper dura mater, thus, in their position, corresponding 

 with the plexus venosi spinales. The arachnoid membrane, 

 either of the spinal cord or of the brain, contains no proper vessels 

 (vid. Luschka, 1. c, p. 71), whilst the pia mater in both situa- 

 tions supports not only the very copious ramifications of the 

 vessels of the nervous substance itself, but is also supplied, with 

 a tolerably rich, proper capillary plexus of its own. In one 

 portion of the pia mater, viz. in the vascular plexuses, the 

 vessels are distributed solely in the membrane itself, the 

 branches entering the nervous substance being of subordinate 

 importance. Lymphatics it is said have recently been injected 

 with air and quicksilver by Fohmann and Arnold, (vid. ' Anat.' 

 II, p. 618) both in the pia mater on the surface of the cerebrum 

 and cerebellum, as well as in the choroid plexus, but this 

 observation appears to me very much to demand confirmation. 

 The membranes of the central nervous system, also contain 

 nerves, at all events in part. In the dura mater of the cerebrum 

 they run in the periosteal lamella of the membrane, following 

 pretty nearly the course of the meningeal arteries, and are 

 especially distinct on the a. meningea media, which is accom- 

 panied, not only by twigs of the nervi molles, but also by a 

 special nerve first noticed by Arnold (n. spinosus, Luschka), 

 which, according to Luschka, is derived from the third branch 

 of the n. trigeminus, the former of which are distributed with 

 the vessels, and the latter appears to be destined principally 

 for the bones. Besides these, Purkinje has noticed nerves on 

 the anterior and posterior meningeal arteries, and Arnold long 

 ago described the well-known n. tentorii cerebelli, proceeding 

 from the fifth pair, which, as has been lately shown, particularly 

 by Pappenheim and Luschka (1. c), goes to the larger sinuses 

 of the dura mater. The elements of this white looking nerve 

 and of the n. spinosus of Luschka, are those of the n. trigeminus, 

 those of the others, fine fibres, and in both situations they pre- 

 sent divisions. In the dura mater of the spinal cord, I, as 

 well as Purkinje, have been unable to detect any nerves ; they 

 occur, however, as has been already mentioned, in the peri- 

 osteum of the vertebral canal, and on the arteries going to the 



