GUIDE TO THE HEAD AND NECK tsgx 



of the ligamenta subflava, and the interspinous and supraspinous ligaments. 

 The spinal canal having been laid open, the dissector wnll expose the epidural 

 space, occupied by loose areolar tissue, embedded in which there is a copiou3 

 plexus of veins and spinal arteries. The arteries of the spinal canal and spinal 

 cord, though usually uninjected, are to be studied from the description given 

 of them in the text, and, in association with the arteries, the veins are to receive 

 attention. 



Meninges of the CorA. — The dura mater, forming the theca, the zu-achnoid, 

 and the pia mater, are to receive the most careful attention. The outer 

 surface of the dura mater will be readily exposed by removing the areoleir 

 tissue and plexus of veins already referred to. The dissector will easily be 

 able to show the tubular sheaths which the dura mater furnishes on either 

 side to the spinal nerves as these pass through it, these sheaths being pro- 

 longed into the intervertebral foramina. 



The dura matral theca is now to be carefully laid open along the middle 

 line with a pair of scissors. This will expose the narrow interspace known 

 as the subdural space. This space having been studied, attention is to be 

 directed to the arachnoid membrane, beneath which is a wide interspace, 

 called the subarachnoid space. In studying this space the dissector is to 

 make himself familiar with its division into three compartments by means 

 of the septum posticum, posteriorly, and the ligamenta denticulata, one on 

 either side. The arachnoid membrane having been carefully removed, the 

 pia mater is to be studied. Its very intimate relation to the spinal cord 

 wUl be at once evident, and in connection with it the ligamenta denticulata, 

 right and left, should receive careful attention. The manner in which the 

 ligamenta denticulata act as suspensory ligaments to the spinal cord will be 

 evident. 



The spinal cord, along with the dura mater, is now to be removed from 

 the spinal canal. In doing so the dissector should be careful to remove, at 

 the same time, the lateral prolongations of the dura mater ■■ into the inter- 

 vertebral foramina, containing the spinal nerves. For this purpose the inter- 

 vertebral foramina may be laid open with the bone-pliers, and the actual 

 dissection of a spinal nerve may be accomplished at this stage, if the dis- 

 sector prefers it. 



The external characters of the cord are then to receive the most careful 

 attention. The glistening band, called the linea splendens, is to be 

 noted on the anterior surface of the cord, over the course of the anterior 

 median fissure. The cervical and lumbar enlargements are to be noted. 

 The mode of origin of a spinal nerve by two roots is to be made evident, 

 and the ganglion on the posterior root is to be shown. The union of the 

 two roots immediately outside the ganglion, to form a spinal nerve, should 

 be shown, as well as the division of the spinal nerve into anterior and 

 posterior primary divisions. The anterior median and posterior median 

 fissures, as well as the postero-lateral sulcus, are to receive attention. The 

 antero-lateral and posterior colunms are to be studied, as well as the columns 

 of GoU and of Burdach. At the lower end of the cord the conus meduUaris 

 will be seen, and the aurrangement of nerves, known as the cauda equina, will 

 attract attention, in the centre of which leash the filum terminaie can be 

 shown without difiiculty. 



When the dissector has studied the external characters of the cord, he 

 should endeavour to harden it by immersion in the ordinary fluid used for 

 the preservation and hardening of the brain. This process will occupy 

 three or four weeks, after which time transverse sections should be made 

 through the cord at various levels. This will give the dissector some know- 

 ledge of the internal structure of the cord. 



The Brain. — The brain, it is assumed, has been sufficiently hardened by 

 immersion in the fluid used for this purpose. In their operations upon this 

 organ it is absolutely necessary that the dissectors should treat it with the 

 most scrupulous gentleness, supporting it on all sides where necessary, and 

 always keeping those parts which are not under immediate dissection or 

 observation covered with cloth saturated with the hardening fluid. With 

 these general precautions the brain should be placed on a wooden platter. 



