1002 



to the bone, and reflect the flaps on either side. Detach as much of the 

 temporal muscle from the bone as is necessary to get room for two 

 trephine holes, the internal borders of which must be not less than 

 J inch from the middle line, so as to avoid wounding the longitudinal 

 sinus. Carefully work the trephine through the skull, taking care not 

 to press heavily on it at the last. Raise up the two pieces of bone with 

 forceps, connect the holes with bone forceps, and enlarge the opening as 

 much as may be necessary to reach all the ' motor ' areas. At this 

 stage only enough ether should be given to prevent suffering. Now 

 unbind the hind- and fore-limbs on the side opposite to that on which 

 the brain has been exposed, apply blunt electrodes successively to the 

 areas for the fore- and hind-limbs, and stimulate.* The ' unipolar ' 

 method of stimulation (p. 951) may also be employed. Contraction of 

 the corresponding groups of muscles will be seen if the narcosis is not 

 too deep. Movements of the head, neck, and eyelids may also be called 

 forth by stimulating the ' motor ' areas for these regions. Stimulation 

 in front of the crucial sulcus may also cause great dilatation of the pupil, 

 the iris almost disappearing. The dilatation takes place most promptly 

 and is greatest on the opposite side, but the pupil on the same side is 

 also widened. Even after section of both vago-sympathetic nerves in 

 the neck, a slow and slight dilatation, greatest perhaps on the same side, 

 may be caused by cortical stimulation. Repeat the whole experiment 

 on the opposite side of the brain. In the course of his observations the 

 student will perhaps have the opportunity of seeing general epileptiform 

 convulsions set up by a localized excitation. They begin in the group 

 of muscles represented in the portion of the cortex directly stimulated. 

 After the convulsions have been sufficiently studied, they should be 

 again induced, and the stimulated ' motor ' area rapidly excised during 

 their course. In some cases this will be followed by immediate cessation 

 of the spasms, (c) The same animal can be used for stimulation of the 

 spinal nerve-roots, as described in Experiment I (p. 995). 



It is not necessary to remove the dura mater. 



