CENTRAL NERVOUS SYSTEM 103 



of absorbent cotton containing ether. Slit and retract the skin 

 over the skull and remove a triangular piece of the latter so as 

 to expose the cerebrum. The base of the triangle should be 

 on a line connecting the posterior border of the tympanic 

 membranes and should be about a centimeter wide. Avoid 

 injury to the brain beneath until the cerebrum is completely 

 exposed, then carefully remove the latter and plug the cavity 

 loosely with cotton. Sew the skin in place and keep the animal 

 where the skin will remain moist until the next day. This 

 can be done by placing the frog with a little water in an evaporat- 

 ing dish and covering all with a large funnel or something which 

 will prevent escape, but at the same time allow access of plenty 

 of air. 



After 24 hours study the behaviour of the decerebrate 

 animal compared with a normal frog, noticing especially: 

 posture, ability to swim or hop, power of escaping from a vessel 

 of water gradually heated, ability to turn over when placed on 

 the back. 



Again open the cranial cavity, without anaesthesia as there 

 can be no sense of pain, and destroy the corpora stria ta and 

 optic thalami. After recovery from shock observe the activities 

 as before. Finally destroy the rest of the brain and notice any 

 change in behaviour. 



