FIXATION OF ELECTRODES 



to the surface. The details of the technique are shown as Figures 36.2 and 

 36.3. 



With unipolar electrodes a suitable indifferent electrode can be made 

 from a silver plate placed subcutaneously over the anterior part of the 



Electrodes in 

 resin block 



Periosteum 



Brain 



Bone 

 Dura mater 



Clamp holding protruding electrode 



cement holding electrodes- 

 II and screws 



Protruding wire 

 cut off and 

 covered 

 cement 



Electrodes in 

 position 



Skin suture 



s leads 



Leads brought through 

 skin away from 

 electrodes 



Figure 36.3 Fixation of electrodes in brain 



skull. It is important that the plate should not be placed on the posterior 

 of the head as the movements of muscles in that region can cause displace- 

 ment of the plate which may damage both the leads to the electrode and 

 the animal. 



Suitable insulating material for imbedded electrodes includes most of 

 the modern synthetic resins with the required electrical properties except 

 the phenol formaldehyde group, many of which give rise to tissue reactions 

 if left in the body for long periods. The polyester resins should be mixed 

 with a minimum of accelerator and catalyst if they are to be used for 

 insulating or 'potting' small electrical components that are to be buried 



573 



