PRACTICAL EXERCISES 



769 



are clipped off the head, an incision made in the middle line through 

 the skin, and the flaps reflected so as to expose the skull. Cut 

 through the bones with scissors, and make a sufficiently large opening 

 to bring the cerebral hemispheres into view. They are now rapidly 

 divided from the corpora bigemina and lifted out with the handle of 

 a scalpel. The bleeding is very free, but may be partially controlled 

 by stuffing the cavity with the vegetable fibre known as Pengavar 

 Djambi. which should be removed in a few minutes, the wound 

 cleansed with iodoform gauze wrung out of normal salt solution at 

 50 C., and sewed up. Study the phenomena 

 described on p. 740. 



6. Stimulation of the Motor Areas in the 

 Dog. (a) Study a hardened brain of a dog, 

 noting especially the crucial sulcus (Fig. 742), 

 the convolutions in relation to it, and the 

 areas mapped out around it by Hitzig and 

 Fritsch and others, (b) Inject morphia under 

 the skin of a dog. Set up an induction-coil 

 arranged for tetanus, with a single Daniell in 

 the primary circuit. Connect a pair of fine 

 but not sharp-pointed electrodes through 

 a short-circuiting key with the secondary. 

 Fasten the dog on the holder, belly down, 

 and put a large pad under the neck to sup- 

 port the head. Clip the hair over the scalp. 

 Feel for the condyles of the lower jaw, and 

 join them by a string across the top .of the 

 head. Connect the outer canthi of the eyes 

 by another thread. The crucial sulcus lies 

 a little behind the mid-point between these 

 two lines. Now give the dog ether if neces- 

 sary, make a mesial incision through the skin 

 down to the bone, and reflect the flaps on 

 either side. Detach as much of the tem- 

 poral muscle from the bone as is necessary 

 to get room for two trephine holes, the 

 internal borders of which must be not less 

 than \ inch from the middle line, so as to 

 avoid wounding the longitudinal sinus. Care- 

 fully 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."* Contraction of the corres- 



FIG. 273. BRAIN OF 

 FROG. (AFTER 

 STEINER.) 



<z, cerebral hemispheres ; 

 6, position of optic thalami ; 

 c, optic lobes ; d, cerebel- 

 lum ; e, medulla oblongata; 

 A, upper end of spinal 

 cord. 



* It is not necessary to remove the dura mater. 



49 



