PR/iCT!CAL DIRECTIONS. 463 



already been done. (If a fresh specimen is used, and the head is to 

 be employed for other purposes, the brain can be removed without 

 separating the head from the body, and without taking away the 

 lower jaw and other structures on the ventral surface of the skull.) 



Have at hand dissecting-instruments and a dish containing 

 alcohol and formalin in the following proportions (Parker and 

 Floyd's mixture) : 



95 per cent, alcohol 6 parts 



2 per cent, formalin 2 parts 



In the bottom of the dish should be placed a little absorbent 

 cotton, to support the brain. 



In removing the brain have at hand entire and dissected skulls 

 and note the relations of parts on these as far as necessary before 

 cutting the specimen. 



With bone-forceps make a small opening in the parietal bone so 

 as to expose the dura mater, but do not cut through the dura mater. 

 With some blunt instrument free the dura mater from the bone about 

 the opening, and continue to cut away the bone until the dorsal and 

 lateral faces of the cerebrum are fully exposed craniad of the 

 tentorium. The olfactory bulbs (Fig. 137, /) should be exposed 

 carefully and as fully as possible. Cut away the dorsal arch of the 

 atlas and carefully insert the forceps in the foramen magnum and, 

 working as before, remove the squamous portion of the occipital and 

 tlie parietal bones as far as the tentorium and as far ventrad as 

 possible. Leave the dura mater intact if possible. Free the surface 

 of the tentorium from the dura mater, carefully separate slightly the 

 cerebellum and cerebrum; insert the bone-forceps (not too far) with 

 the blades inclined from without ventromediad, and cut the tentorium 

 on each side. Remove it slowly, cutting adhesions to the dura 

 mater. That part of the dura mater which dips between the cerebral 

 hemispheres is the falx cerebri. Cut the dura mater along both sides 

 of the falx cerebri and remove it by turning it down at the sides and 

 cutting it at the level of the cut edge of the bone. Remove it also 

 from the cerebellum and notice how it dips down on both sides of 

 the tentorium and in close contact with it. Cut the falx at the 

 cranial end between the olfactory bulbs and cut the tentorial dura 

 (cut its adhesions, but do not remove with it the pineal body). The 

 falx and tentorial dura may then be removed. 



Allow the head to hang sideways over the dish of alcohol-formalin 

 in such a way that the brain will tend to fall out of the cranium. 

 Free the olfactory bulbs from the bone. Then begin at the caudal 

 end and tilt the brain out with the handle of a scalpel. In doing 

 this note carefully and cut the cranial nerves. They should be left 

 with central ends as long as possible, and those on the side which is 

 uppermost should be cut first. In doing this refer to the foramina 

 in the base of the skull and to Fig. 138. Take especial pains also 

 not to break off the hypophysis, which is lodged in the sella turcica. 



