GLANDULiE PACCHIOXI. 575 



fifth, the facial, and accessorius nerves ; and the}- have likewise been 

 followed by Luschka. 



Cerebro-spinal fluid. — This is a very limpid serous fluid, which 

 occupies the subarachnoid space. When collected immediately after 

 death, its quantity was found by Magendie in the human subject to 

 vary from two drachms to two ounces. It is slightly alkaline, and con- 

 sists, according to an analysis by Lassaigne, of 08-5 parts of Avater, 

 the remaining I'o per cent, being solid matter, animal and saline. In 

 experiments made on the dog, it was found by Magendie to be repro- 

 duced in thirty-six hours, after it had been drawn off by puncturing 

 the membranes at the lower part of the cord. When pressure is made 

 upon the brain, the quantity of fluid in the spinal subarachnoid space 

 is increased, and conversely, it may be forced from the spinal cavity 

 upwards into the cranium, 



Ligamentum denticulatum. — This is a narrow fibrous band which 

 runs along each side of the spinal cord in the subarachnoid space, 

 between the anterior and posterior roots of the nerves, commencing 

 above at the foramen magnum, and reaching down to the lower 

 pointed end of the cord (fig! 395, 12, and fig. 345). By its inner edge 

 this band is connected with the pia mater of the cord, while its outer 

 margin is widely denticulated ; its denticulations are attached by 

 their points to the inner surface of the dura mater, and thus serve to 

 support the cord along the sides, and to maintain it in the middle of 

 the cavity. The first or highest denticulation is fixed opposite the 

 margin of the foramen magnum, between the vertebral artery and the 

 hypoglossal nerve ; the others follow in order, alternating with the 

 successive pairs of spinal nerves. In all, there are about twenty-two 

 of these points of insertion. The denticulations in the lower cervical 

 region are very long, and ascend shghtly to their attachments. At the 

 lower end, the ligamentum denticulatum may be regarded as continued 

 into the terminal filament of the spinal cord, which thus connects it to 

 the dura mater at the lower end of the sheath. The free edge, in the 

 intervals between the denticulations, is slightly thickened, and, in the 

 body, is closely applied to the inner surface of the arachnoid, with which 

 it is often directly connected by fine trabecule. The denticulations do 

 not perforate the arachnoid but receive from it funnel-shaped sheaths, 

 wdiich accompany them to the imier surface of the dura mater. (Axel 

 Key and Retzius, Max Schultze's Archiv. 1873). 



Sirudure. — It consists of white fibrous tissue, mixed with many ex- 

 ceedingly fine elastic fibres which are seen on applying acetic acid. 

 Several layers of fine connective tissue trabecule may be traced : they 

 are surrounded by sheaths, which are composed of delicate nucleated 

 cells, and here and there expand into membranes. It is continuous 

 on the one hand with the fibrous tissue of the pia mater, and on tlie 

 other with that of the dura mater. 



Glandulae Facchioni. — Upon the external surface of the dura matei', 

 in the vicinity of the longitudinal sinus, are seen numerous small pulpy 

 looking elevations, generally collected into clusters, named glands of 

 Pacchioni, The inner surface of the calvarium is marked by little pits, 

 which receive these prominences. Similar excrescences are seen on the 

 internal surface of the dura mater, and upon the pia mater on each side 

 of the longitudinal sinus, and also projecting into the interior of that 

 sinus. Occasionally they are found also in other situations. 



