A MANUAL OF PHYSIOLOGY 



(b) Stimulate with a weak interrupted (faradic) current the central 

 stump of one of the nerves of a hind-limb say, the peroneal nerve. 

 The flexion reflex of the same limb may be elicited. Record the 

 movements. Now produce temporary asphyxia by clamping the 

 respiration tube, and repeat the stimulation at half-minute intervals. 

 The reflex will be increased by the asphyxia. Do not interrupt the 

 respiration for more than two or three minutes, and immediately start 

 it if the heart, which can be felt through the chest, begins to weaken. 



(3) Elicit the knee-jerk, as described in the 

 text (p. 802). It is generally exaggerated. 



(4) By the unipolar method (p. 843) stimu- 

 late with a point electrode one lateral half of 

 the cross section of the cervical cord exposed 

 in decapitation. The large electrode is placed 

 on a shaved part of a iorearm. Various- effects 

 may be elicited according to the point of the 

 cross section stimulated e.g., stepping and 

 scratch movements of the hind limbs. Other 

 facts mentioned in the text in regard to spinal 

 reflexes can be verified on this preparation. 



9. Reflexes in Man. Study systematically 

 on a fellow-student and on yourself the chief 

 reflexes described in the text (p. 810). 



10. Excision of Cerebral Hemispheres in the 

 Frog (Fig. 368). Anaesthetize a frog lightly 

 by putting it under a bell-jar or tumbler with 

 a small piece of cotton-wool soaked in ether. 

 Put very little ether on the cotton, and leave 

 the frog only a very short time under the bell- 

 jar. Then, holding it in a cloth, make an 

 incision through the skin over the skull in 

 the mesial line. With scissors open the 

 cranium about the position of a line drawn 

 at a tangent to the posterior borders of the 

 two tympanic membranes. Remove the roof 

 of the skull in front of this line with forceps, 

 scoop out the cerebral hemispheres, and sew 

 up the wound. As soon as the animal has 

 recovered from the ether, the phenomena 

 described at p. 840 should be verified. The 

 frog will swim when thrown into water, will 

 refuse to lie on its back, and will not fall if 

 the board on which it lies be gradually slanted. 

 Let the frog live 1 for a day, keeping it in a moist 

 atmosphere ; then expose the brain again, 



determine the reflex time by Tiirck'S method ; apply a crystal of 

 common salt to the optic lobes, and repeat the observation. The 

 reflex movements will be completely inhibited or delayed. Remove 

 the salt, wash with physiological salt solution, excise the optic lobes, 

 and see whether the frog will now swim. 



ii. Excision of the Cerebral Hemispheres in a Pigeon. Feed a 

 pigeon for two or three days on dry food, etherize it by holding 

 a piece of cotton-wool sprinkled with ether over its beak, or inject 

 into the rectum | gramme chloral hydrate. The pigeon being 

 wrapped up in a cloth, and the head held steady by an assistant, 

 the feathers are clipped off the head, an incision made in the middle 

 line through the skin, and the flaps reflected so as to expose the 



FIG. 368. BRAIN OF 

 FROG (AFTER 

 STEINER). 



a, cerebral hemi- 

 spheres ; b, position of 

 optic thalami ; c, optic 

 lobes ; d, cerebellum ; 

 e, medulla oblongata ; 

 A, upper end of spinal 

 cord. 



