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EXERCISE XVIII 



isolated. In thus separating and dissecting out the tibial nerve take care not 

 to injure the peroneal nerve ; the latter is the motor nerve of the muscle whose 

 contraction you will study. The tibial nerve you will use as the afferent 

 nerve, from which to evoke reflex contraction of the muscle. Replace the 

 nerve in the wound and close the skin with a clip. 



III. V. (PI. IX, fig. 7.) Insert a steel drill (text-fig. 38) into the lower end 

 of tibia and fibula of the left leg from within outwards parallel with main 



Text-fig. 38. Drill for inserting drill-pins into femur and tibia to fixate 

 the limb for the myograph. The drill-pin screws into the drill-head for 

 insertion, and is then left in the bone by unscrewing the drill-head from 

 it ; the brass rod at top of figure is bored, at its left-hand end in figure, 

 with a screw-thread, enabling it to screw on to the inserted drill-head ; 

 the rod is then fixed by a clamp to a vertical or other standard as required 

 for fixating the limb. 



ankle-joint surface of tibia and about 5 mm. above the joint. Expose the 

 inner face of the inner condyle of femur ; insert a steel drill through lower 

 end of femur from within outwards and parallel with the drill through 

 tibia fibula. 



Place the preparation on its right side. 



Screw on to the brass ends of the two drill-pins the two brass rods 

 provided and clamp these latter to the heavy based standards provided, 

 arranging that they hold the leg-shank nearly horizontal, with its distal 

 end directed toward the myograph-lever, but with the ankle somewhat lower 



