190 



THE CEEEBEAL HEMISPHERES. 



parts is closely applied to the inner surface of the arachnoid, with which it is often 

 directly connected by fine trabeculse. The denticulations do not perforate the 

 arachnoid but receive from it funnel-shaped sheaths, which accompany them to the 

 inner surface of the dura mater (Axel Key and Ketzius). 



In structure the ligament consists of white fibrous tissue, mixed with many 

 exceedingly fine elastic fibres. Several layers of fine connective tissue trabeculas 

 may be traced ; they are surrounded by sheaths, which are composed of delicate 



Fig. 133. VIEW FROM BEHIND OF THE MEDULLA OBLONGATA AND SPINAL CORD, WITH THE THECA. 



(Sappey.) . 



The dura-matral sheath has been opened by a median incision and is stretched to either side. In 

 the upper and middle parts (A and B) the posterior nerve-roots have been removed to show the ligamentuin 

 denticulatum. 1 , fourth ventricle ; 2, 3, 4, cerebellar peduncles ; 5, clavus ; 6, 7, 8, roots of glosso- 

 pharyngeal, vagus, and accessory nerves ; 9, points of ligamentum denticulatum ; 10, line of entrance of 

 posterior roots into spinal cord ; 11 (in B), posterior median fissure; 12, ganglia ; 13, cut anterior roots ; 

 14, mixed nerve ; 15, 16, filum terminate ; 17, cauda equina. 



nucleated cells, and here and there expand into membranes. Its tissue is continuous 

 on the one hand with that of the pia mater, and at the apices of the denticulations 

 with that of the dura mater. 



Glanclulce Faccliionii or arachnoidal villi. Upon the external surface of the 

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

 looking elevations, generally collected into clusters, named glands of Pacchioni 

 (fig. 134). The inner surface of the calvaria 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 (s). Occasionally they are found 

 also in other situations. 



On a careful examination of the connections of these bodies it will be found that 



