240 



LABORATORY MANUAL OF HUMAN ANATOMY 



prolongation of the arachnoid over the nerve roots and over the 

 summits of the teeth of the liganientuin denticulatum. 



Lift the visceral layer of the arachnoid, cut through it with 

 fine scissors, insert grooved director, and cut it open longitudi- 

 nally a little to one side of median line. Examine the space 

 (cavum subarachnoideale) beneath the visceral layer of the 

 arachnoid and the pia mater. Note the expanse of the space 

 especially in the region of the cauda equina, which it contains. 



FIG. 99. 



A 



Portions of the pars cervicalis of the spinal cord with nerve-roots. 



A, spinal cord seen from the ventral surface. On the right side the ventral fila radicularia have 

 been cut through. S, spinal cord seen from the lateral surface. 1, fissura mediana anterior ; 2, sulcus 

 medianus posterior ; 3, sulcus lateralis ventralis, whence the ventral fila radicularia emerge ; 4, sulci 

 laterales dorsales through which the dorsal root fibres enter the spinal cord ; 5, radix ventralis going 

 past spinal ganglion cut through on the right side in Fig. A ; 6, radix dorsalis emerging from the 

 ganglion spinale (&) 7, N. spinalis immediately after its formation through the union of the radix 

 ventralis and dorsalis dividing into 7, a ramus ventralis, and 7', a ramus dorsalis. The ramus com- 

 municans and the ramus meningeus are not shown in this figure. (After Allen Thompson, from A. 

 Rauber, Lehrbuch der Anatomie des Menschen, V. Aufl., Leipz., 1898, Bd. ii. S. 283, Fig. 248.) 



Where would the cerebrospinal fluid accumulate in greatest 

 amount? Note precise spot where cavum subarachnoideale is 

 tapped in Quincke's lumbar puncture. There is no communica- 

 tion between the cavum subdurale and the cavum arachnoideale. 

 Notice the areolar tissue everywhere present between the arach- 

 noid and the pia. Make out the septum subarachnoideale pos- 

 terius. 



Examine the spinal pia mater (pia mater spinalis). How 



