426 ANATOMICAL TECHNOLOOY. 



In using the nippers, another precaution is to be observed.. If the bit of bone to be 

 removed is attached only to bone, it may be either cut or broken or twisted off ; but if it 

 adheres to the dura or other soft parts, only cutting should be employed ; it is safer to 

 use the bone scissors after nipping the bone. 



When any bit of the skull is broken off, lift it very carefully, and examine its eutal 

 aspect for nerve attachments. 



During the exposure of the brain, the head should be frequently dipped into the n. s. s. 

 If obliged to suspend the operation for more than an hour, wrap the head in a cloth wet 

 with the n. s. «., and set in a cool place. 



Trim off the soft parts, including the meatus auditorius. Nip 

 off the caudal root of the zygoma, including the Fs. mandibularis. 

 Insert a nipper blade into the meatus auditorius, and remove the 

 bulla in fragments. With the scissors, cut away the membranes 

 attached to the margin of the Fm. magnum. 



Nip off the occipital condyles, with the intei-vening area of the 

 hasioccipital for 2-3 mm. 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. Tiypoglossus enters the Fm. condylare, and 

 passes cephalad to emerge on the ventral aspect of the skull by the 

 Fm. jugulare. If the series of roots do not appear, carefully re- 

 move a little more bone until they do. If the nerve roots are to be 

 specially studied, endeavor to nip off the bone surrounding the 

 Ftii. condylare, so as to save the trunk. On emerging upon the 

 ventral aspect of the skull, the N. Iiypoglossus wUl be found to lie 

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

 attached to the NN. glossopharyngeus, vagus and accessorius, 

 which penetrate the bone by that foramen. In attempting to sepa- 

 rate the jy. Tiyp., 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 distinguished, 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 roots 

 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 ectal nerve origins. 



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



