1593 A MANUAL OF ANATOMY 



the base being at first downwards, and a kind of nest having been made for 

 it on the platter with pieces of cotton wadding, saturated with the hardening 

 fluid. Two small wedge-shaped blocks should also be in constant use, each 

 being insinuated gently underneath the lateral aspect of the corresponding 

 cerebral hemisphere. These blocks the dissectors will find to be of great 

 utility in keeping the parts of the brain together. 



The superior surface of the brain is to receive the most careful attention, 

 and the dissectors are recommended to study the description given of it in 

 the text. 



The brain is now to be reversed, and placed in its nest with the base up- 

 wards. In doing so it must be handled with the greatest gentleness. The 

 dissectors have been already advised to study the base immediately after 

 the removal of the brain from the cranial cavity. It will, however, well 

 repay them to renew this examination in view of the importance of the parts 

 here exposed for their careful study, e.g., (i) the component parts of the 

 encephalon ; (2) the superficial origins of the cranial nerves, including the 

 olfactory lobes ; (3) the arteries, including the circle of Willis ; (4) the cisternse 

 beneath the arachnoid, and so on (see the description given of all these in 

 the text). 



A careful effort may be made to follow out the leading arteries, but this 

 is on no account to be pushed, as, to do so, might endanger structures of con- 

 siderable importance. The branches of each vertebral artery may admit of 

 reasonable dissection ; so also may those of the internal carotid. The dis- 

 sectors will find a description of the arteries in the text, and their special 

 attention is drawn to the lenticulo-striate arteries. If the fissure of Sylvius 

 has not been already opened up, that should now be carefully done, in order 

 to see the gyri operti of the insula or island of Reil, lying deeply at the bifurca- 

 tion of the fissure. 



The bloodvessels and membranes are now to be carefully removed from 

 the base of the brain, except in the interval between the cerebellum and 

 medulla oblongata. For this purpose the forceps will be sufficient, aided 

 occasionally by a pair of scissors. In doing so there is considerable risk of 

 taking away the cranial nerves, but this must not be done. The inter- 

 peduncular region may now be studied, and the superficial origins of the 

 cranial nerves revised, the olfactory lobe also receiving attention. 



The dissectors are now advised to reverse the position of the brain, and 

 to proceed with a systematic dissection of all its parts ; but they must be 

 prepared to encounter considerable difficulties, as it is not an easy matter 

 to lay down hard-and-fast directions. It may be further stated that the 

 brain should be dissected several times, and in different ways. 



The brain being now placed with its base downwards, the fissures, lobes, 

 and gyri of the cerebral hemispheres, in so far as they are visible, are to be 

 thoroughly mastered, special attention being directed to (i) Broca's lobe; 



(2) the fissure of Rolando, and the gyri which bound it in front and behind ; 



(3) the parieto-occipital fissure ; and (4) the three limbs of the fissure of Sjivius. 

 The opercula insulae are also to be studied. 



The cerebral hemispheres are then to be sliced away with a long knife 

 until the level of the corpus callosum is reached. In doing so the dissector 

 is to note the white matter in the centre, surrounded by the grey cortex. 

 The corpus callosum is to be carefully inspected from above, the raph6, striae 

 longitudinales mesiales, and striae longitudinales laterales being noted. The 

 anterior cerebral arteries will also be seen sweeping backwards upon the corpus 

 callosum. The forward and backward extent of the corpus callosum is also 

 to be attended to. 



Lateral Ventricles. — These ventricles are to be opened by means of two 

 longitudinal cuts through the corpus callosum, each cut being made about 

 J inch from the median line. Each ventricle is then to be laid completely 

 open, so as to show the anterior and posterior cornua, by removing as much 

 of the hemisphere as may be necessary. The various structures exposed in 

 the floor of the lateral ventricle are to be carefully studied, namely, (i) the 

 nucleus caudatus of the corpus striatum in the anterior cornu ; (2) the taenia 

 semicircularis, and the vein of the corpus striatum ; (3) a portion of the 



