770 A MANUAL OF PHYSIOLOGY 



ponding 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 repre- 

 sented 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. 



7. Eemoval of the Motor Areas on One Side in the Dog. Proceed 

 as in 6, but use antiseptic precautions, and instead of stimulating, 

 destroy with the actual cautery or remove with the knife all the grey 

 matter around the crucial sulcus on one side. Stop bleeding by 

 iodoform gauze wrung out of hot normal saline solution. Sew up 

 the muscles by one set of sutures, the skin by another, and cover the 

 wound with collodion. When the dog has recovered from the 

 operation, study the deficiency of motor and sensory power on the 

 opposite side (p. 747). (Fig. 265, p. 743.) 



