lubes and the cerebrum and remove it. With silk thread MW together 

 the flaps of the skin. 



Xote the posture of the animal immediately after the operation. 

 To what factors may this be due? While the animal is recovering 

 perform other experiments. During the interval, however, keep 

 the frog's skin moist, for he breathes in large part through his 

 moist skin. In about an hour test the capabilities of the frog as 

 follows : ( a ) Posture. Record the difference between the decerebrate 

 frog and a spinal frog as to posture. (b) Locomotion. Simi- 

 larly record the differences in leaping and swimming. ( c ) Respira- 

 tion. Is there a difference in respiratory activity? (d) Vision. 

 Compare the eyelids. Place an opaque object between the decere- 

 brate frog and a source of light. With the animal facing the object, 

 which should be only 6 or 7 cm. distant, stimulate him to jump. 

 Does the frog jump against the object, or avoid it? (e) Equilibra- 

 tion. Turn the decerebrate frog on his back. Compare his reaction 

 to that of a spinal frog. Place him on the palm of the hand or on 

 the frog board. Slowly tilt his support. What happens as his 

 equilibrium is disturbed? See if the frog can be made to crawl 

 to the other side of the hand or frog board as the support is fur- 

 ther turned. ( f ) Croak reflex. Hold the decerebrate frog gently 

 between the thumb and first finger, placed immediately behind the 

 front limbs. Apply slight pressure for a moment. The frog should 

 croak in response to each application of stimulus. Stroke with the 

 moistened finger the skin of the back or flanks, and note if this 

 also evokes a reflex. 



(g) If the operation is successful the animals live for several days. 

 They will be kept in the laboratory, and if possible the student ought 

 to examine their general reactions on the clay after the operation. 



229. Influence of optic lobes on refle.res. Endeavor to find some 

 marked difference between a decerebrate and a normal frog. a. 

 Expose the brain according to the directions already given. Imme- 

 diately posterior to the hemispheres lie the optic lobes, two gray 

 spherical bodies. Separate the cerebral hemispheres from the optic 

 lobes by a transverse incision, and carefully remove the hemispheres. 

 Wait until the shock of the operation has passed. Xo\v suspend the 

 frog without injury so that the tips of the toes hang above a shallow 

 dish containing 0.5 r ; sulphuric acid. Determine the reflex time. 

 Wash off the acid and, after a moment's rest, sprinkle a very 

 little finely powdered common salt on the cut surface of the 

 optic lobes. Again determine the reflex time. Is it markedly 

 changed by the stimulation of the optic lobes? 



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