120 ADVANCED LESSONS IN PRACTICAL PHYSIOLOGY 



Weaken the strength of the current considerably by moving the 

 secondary coil farther away from the primary. Stimulate the nerve in 

 the same manner with single induction shocks repeated at intervals of 

 about half a second. This procedure usually gives rise to a reflex vaso- 

 dilatation, and hence to a fall in the carotid blood-pressure. Conse- 

 quently, the sciatic nerve contains vasoconstrictor as well as vaso- 

 dilator fibers. Kill the animal by an overdose of ether. 



Annotation. In isolating the sciatic nerve make use of the following landmarks: 

 Seek a point midway between the ischium and great trochanter of the femur, and 

 draw an imaginary line from here to the anterior aspect of the knee-joint. Direct 

 the incision along this line about the middle of the thigh and separate the adjoining 

 muscles until the fatty tissue investing the sciatic nerve has been exposed. 



