510 



DISSECTION OF THE HEAD. 



How to pre- 

 serve the 

 brain. 



Examina- 

 tion of it. 



Directions. 



Dura mater 

 in base of 

 skull : 



its prolonga- 

 tions, 



and connec- 

 tions to 

 bone. 



Tentorium 

 cerebelli : 



taken readily from the skull in the two hands. In doing this 

 some large veins, passing from the hinder part of the cerebral 

 hemisphere to the attached margin of the tentorium, will be broken 

 through, as well as small ones from the portions of the brain in the 

 posterior fossa of the base of the skull. 



PRESERVATION OF THE BRAIN. After removing some of the mem- 

 branes from the upper part, and making a few apertures through 

 them on the under surface so that the liquid may have free access, 

 the brain may be hardened by immersion in a 5 per cent, solution 

 of formalin in water. Wrap the brain up in a piece of calico, and 

 then place it upside down in a suitable vessel, on the bottom of 

 which some cotton-wool or tow has been spread, and let it be quite 

 covered with the liquid, and insert a little tow or cotton wool 

 between the cerebellum and the occipital lobes. 



EXAMINATION OF THE BRAIN. At the end of two or three days 

 the dissectors should examine the other membranes of the brain 

 and the vessels as described in Section 1 of The Brain. As soon 

 as the vessels have been learnt, the membranes are to be carefully 

 removed from the surface of the brain, without detaching the 

 different cranial nerves at the under surface. The brain may then 

 remain in the preservative liquid till the dissection of the head and 

 neck has been completed, but it should be turned over occasionally 

 to allow the fluid to penetrate its substance, and a little extra 

 formalin added from time to time as fully directed in the Section 

 referred to. 



Directions. After setting aside the brain, the anatomy of the 

 dura mater, and the vessels and nerves in the base of the skull 

 should be proceeded with. For this purpose raise the head to a 

 convenient height, and fasten the tentorium in its natural position 

 with a few stitches. The dissector should be furnished with the 

 base of a dried skull while studying the following parts. 



Dura mater. At the base of the cranium the dura mater is 

 much more closely united to the bones than it is at the top of the 

 skull. Here it follows the different inequalities of the osseous 

 surfaces and sends processes through the several foramina, 

 which join for the most part the pericranium, and furnish sheaths 

 to the nerves. 



Beginning the examination in front, the membrane will be found 

 to send a prolongation into the foramen csecum, as well as a series 

 of tubes through the apertures in the cribriform plate of the 

 ethmoid bone. Through the sphenoidal fissure it joins the peri- 

 osteum of the orbit ; and through the optic foramen a sheath is 

 continued on the optic nerve to the eyeball. Tn the sella turcica 

 the dura mater forms a recess which lodges the pituitary body, and 

 behind the dorsum sellae it adheres closely to the basilar process of 

 the occipital bone. From the latter part it may be traced into the 

 spinal canal through the foramen magnum, to the margin of which 

 it is very firmly united. 



The tenturium cerebelli is the process of the dura mater which is 

 interposed in a somewhat horizontal position between the small 



