INTERNAL PARTS OF THE HEAD. 507 



which is iiix'-rf-.il into the margins and inner surface of the coronoid insertion, 



-> of the lo\ver jaw. 



On the cutaneous surface is the temporal fascia, with the parts relations, 

 superficial to that membrane ; and concealed by the muscle are the 

 deep temporal vessels and nerves which ramify in it. The insertion 

 of the muscle will be seen, and its action explained, in the dissection 

 of the pterygoid region. 



SECTIOX II. 



INTERNAL PARTS OF THE HEAD. 



Dissection. The skull is now to be opened by the workers on Dissection 

 both sides of the head acting jointly, but before sawing through skuuT n th& 

 the bone the dissector should detach the temporal muscle nearly 

 down to the zygoma ; all the remaining soft parts are to be divided 

 by an incision carried round the skull, about one inch above the 

 margin of the orbit at the forehead, and about the same distance 

 above the protuberance of the occipital bone behind. 



The cranium is to be saun in the same line as the incision Precautions 

 through the soft parts, but the saw is to cut only through the 

 outer table of the bone. The student will know when he has bone - 

 reached the diploe by the material on the saw becoming red. 

 The inner table is then to be broken through with a chisel, in 

 order that the subjacent membrane of the brain (dura mater) may 

 not be injured. The skullcap is next to be forcibly detached by 

 inserting the hooked part of the handle of the chisel between the 

 cut surfaces of bone in front and pulling the shell of bone off 

 backwards. The dura mater will then come into view. 



The DURA MATER is the most external of the membranes investing Dura mater ; 

 th j brain. It is a strong, fibrous structure, which serves as an 

 internal periosteum to the bones, and supports the cerebral mass. 

 Its outer surface is rough, and presents, now the bone is separated appearance 

 from it, numerous small fibrous and vascular processes ; but these gurface r 

 are most marked along the line of the sutures, where the attach- 

 ment of the dura mater to the bone is more intimate. Ramifying 

 on the exposed part of the membrane are branches of the large 

 meningeal vessels. 



Small granular masses, Pacchionian bodies, are also seen close to Pacchionian 

 the middle line. The number of these bodies is very variable ; bodies - 

 they are seldom found before the third year, but generally 

 after the seventh, and they increase with age. The surface of the 

 skull is frequently indented by those bodies, especially on the back 

 part of the parietal bone. 



Dissection. For the purpose of seeing the interior of the Cut through 

 dura mater, divide this membrane with scissors close to the dura mater - 

 margin of the skull, except in the middle line before and behind, 

 where the superior longitudinal sinus lies. The cut membrane 



