i6o 



SCIENCE. 



from the foramen. Insert a nipper-blade between the 

 dura and the bone 5-6 mm. from the meson and in 

 line with the mesal border of the cephalic part of the 

 bulla, and nip out the basioccipital as far as the middle of 

 the length of the bulla. At or near the angle left after 

 the removal of the condyle and the basioccipital, the 

 N. hypoglossalis enters the Ftn. condylare, and passes 

 cephalad to emerge on the ventral aspect of the skull by 

 the Fm. jugulare. If the series of roots do net appear, 

 carefully remove a little more bone until they do. If the 

 nerve-roots are to be especially studied, endeavor to nip 

 off the bone surrounding the Fm. condylare, so as to save 

 the trunk. On emerging upon the veniral aspect of the 

 skull, the N. hypoglossalis wdl be found to he practically 

 in the Fm. jugulare, and to be more or less intimately 

 attached to the NN.glossopharyngealis, vagus and acces- 

 sorius, which penetrate the bone by that foramen. In 

 attempting to separate the N. hyp. great care must be 

 used to avoid any traction upon the roots, which readily 

 pull out of the medulla. Of the other three nerves, the 

 accessorius is the most caudal, and the most readily dis- 

 tinguished, but at this stage it is as well to leave them 

 together, simply endeavoring to remove the bone sur- 

 rounding the foramen, and to save the trunks pretty long, 

 at least upon one side. Upon the other, it will save 

 time to cut the roo;s just entad of the skull, and the 

 same may be done on one side with the remaining nerves, 

 or with all upon both sides in case the brain is not to be 

 employed for the study of the apparent nerve-origins. 



The dorsal wall of the bulla is hard, but readily crum- 

 bles between the nippers. It may be removed in small 

 pieces, so as to save the NN. facialis and auditorius 

 which enter the Ftn. auditorium internum, and the 

 little Lobulus appendicularis of the cerebellum which is 

 lodged in a slight fossa just dorsad of the foramen. 



Since no nerves are transmitted by the mesal region of 

 the basis cranii, it may be removed with comparative 

 freedom, as far cephalad as the pituitary fossa where 

 some care is needed to avoid injuring the hypophysis. 



The skull may now be held more securely by the facial 

 region, especially if a towel is employed. In removing 

 the bone at each side of the meson, and just cephalad 

 of the bulla?, great care is required to disengage the 

 nerves which emerge by the FF. ovale, rotundum, and 

 sphenoidale. These nerves, the AW. oculomotorius, 

 trochlearis, and abducens, with the ophthalmic, superior 

 maxillary, and inferior maxillxry divisions of the A'. 

 trigeminus, penetrate the bone more or less obliquely, 

 and are closely sui rounded by dense connective tissue. 



Just cephalad of this series of foramina is the F.op- 

 ticum, and the N. opticus is particularly hard to disen- 

 gage without tearing some of the delicate parts (terma, 

 or lamina tcrminalis, etc.,) which are connected with 

 the chiasma. Since the optic nerves are always easily 

 recognized, it is usually better to cut them pretty short 

 with the scissors, than to run the risk of rupturing the 

 terma. 



The entire maxilla is now to be removed by first nip- 

 ping the interorbital region just cephalad of the fronto- 

 maxillary suture, and tnen, with the bone-scissors, cut- 

 ting tOAard this point from just caudad of the cephalic 

 root of the zygoma. The scissors should be kept as far 

 cephalad as possible, so that the Bulbi olfaclorii may not 

 be injured. This plan serves equally well for some dogs, 

 but with the larger breeds, which have prominent bulbi 

 olf. the interorbital region should be nipped at about the 

 middle of the length of the nasal bones. 



Remove the mesal walls of the orbit, and the turbin- 

 ated bones, using care not to crush the very soft Bulbi 

 olf. The Nervi olf. should be divided, a few at a time, 

 with the scissors or the tip of the scalpel, and all pulling 

 and twisting of the parts must be avoided. 



During the remaining steps of the operation, the head 

 must be held by the parietal regions, and with great care, 

 so as to avoid pressure of the tips of the fingers upon 



the brain. The bone, also, must now be cut by the 

 nippers rather than twisted or broken. Nip off the 

 supraoccipitale, including the dura, as far as the Crista 

 lambdoidalis. To remove the ventral part of the bony 

 tentorium, introduce a nipper-blade between it and the 

 hemisphere on either side, in such a way that the greater 

 convexity is toward the hemisphere rather than the cere- 

 bellum ; the cut is to be made at the level of the Sutura 

 squamosa; the width of the tentorium at this point is 

 about 8 mm., and the nipper-blade should not be intro- 

 duced to a greater depth than that, for fear of 

 injuring the Lobi optici. In closing the blades the head 

 should be held very firmly so that no rotation may occur. 

 The detached ventral piece of the tentorium may be ex- 

 tracted by the forceps, or by the nippers used as forceps, 

 any adhesions being carefully separated with the tracer 

 or scissors. 



Hold the head with the ventral side down, support the 

 caudal divisions of the brain with a disengaged finger, 

 and with tracer and scissors separate the cephalic sur- 

 face of the cerebellum from the tentorium. Then hold 

 the head with its caudal end down, and complete the 

 disengagement of the Bulbi olf. Hold the head over the 

 7 p. c. brine, with the ventral side down, and nip out, 

 piecemeal, a triangular piece of the calvaria, nearly to 

 the tentorium. The mesal adhesions of the dura may be 

 divided with the scissors, but elsewhere the dura is to be 

 left upon the hemispheres. As the hemispheres begin 

 to fall, hold the head so that they are supported by the 

 biine, and then snip all remaining adhesions until the 

 entire brain is free and floats in the liquid. 



Removal of the Dura. — Saturate some cotton 

 with the brine, and place it under the brain, so that about 

 one-third of the organ projects above the surface. Avoid 

 handling and lifting the brain ; move it by shifting the 

 cotton, or by grasping the dorsal portions of the dura. 

 Remove the dorsal and lateral parts of the dura by grasp- 

 ing the free borders left by cutting along the dorsimeson, 

 and cutting out piece by piece with the scissors. Then 

 grasp the falx just dorso-caudad of the Bulbi olf., at the 

 straight transverse fissure- — F. cruciata ; introduce the 

 scissors about 5 mm., and cut the falx. Gently draw the 

 cephalic portion cephalo-ventrad between the Bulbi olf., 

 and remove it. Draw the caudal portion caudad, and 

 carefully cut all its attachments. 



Turn the brain upon its dorsal surface, and remove the 

 vential portions of the dura with great care and in small 

 pieces. Especial pains are needed in connection with the 

 hypophysis and the nerves, and all pulling must be 

 avoided. On one side, at least, it is well to leave the dura 

 still attached to the nerves and the great Gasserian gan- 

 glion upon the N. trigeminus, to be more completely re- 

 moved at the time of the removal of the pia. 



Transfer to the Alcohol.— Place a large spoon 

 or watch-glass at the side of the brain, and pull the cot- 

 ton which supports it, so as to roll it into the glass, rest- 

 ing upon its dorsum. Let the brain slide off into the al- 

 cohol so as to rest on the cotton therein, still with the 

 ventral side up. 



Set the bowl with the alcohol in a cool place, and 

 change the position of the brain at intervals of five to 

 ten hours -during the first three days, by pulling the 

 cotton in various directions. At the end of about three 

 days, transfer the brain to 95 p. c. alcohol, where it may 

 remain indefinitely. For a few days, however, it should 

 rest 'upon cotton, and its position be occasionally 

 changed. 



Weighing the Brain.— If this is to be done, hand- 

 ling the brain may be avoided as follows ; Place the 

 bowl of alcohol into which the brain is to be put, upon 

 the scales, and pour in alcohol of the same strength until 

 it balances an even number of grams, e. g., 400, 410, 

 or 420. While the brain is in the spoon or watch-glass, 

 pour over it some of the same alcohol, and then let the 

 latter drain off as much as possible, by tilting the glass. 



