CEREBRAL LOCALIZATION. 245 



general results are indicated in the accompanying chart. Finally 

 the effect of the application for some time of a very strong stimulus 

 is studied. 



The animal is finally decerebrated. For this purpose a large 

 aneurysm needle is passed through the posterior edge of the trephine 

 hole backwards until the tentorium cerebelli is felt. It is then 

 directed downwards and inwards so as to break across the base 

 of the brain stem just in front of the tentorium. Immediately this 

 is done the respirations are likely to cease or to become very irregular 

 so that artificial respiration must be started. The ether can now 

 be discontinued since the animal is incapable of feeling any pain. 

 The muscles of the extremities are carefully observed from time 

 to time for the onset of decerebrate rigidity and for the appearance 

 of reflex movements, such as the knee jerk and the flexion reflex. 



For the purpose of studying recriprocal innervation* the 

 tendons of the rectus femoris and the semitendinosus are exposed 

 and isolated from adherent aponeurosis on both sides and the 

 tendons are cut after threads have been tied to them. The peroneal 

 nerves are also exposed as they lie under the skin on the inner side 

 of the leg or the dorsum of the foot. After attaching threads and 

 cutting, each nerve is placed in a pair of Sherrington's electrodes 

 attached to an inductorium. The threads on the tendons are con- 

 nected with muscle levers, by means of pulleys or angle levers, 

 and the writing points are arranged so that they write in 

 the same perpendicular on the drum, signal magnets being 

 inserted in the primary circuits of the two inductoria. When the 

 peroneal nerve on one side is stimulated it will be found that the 

 homolateral semitendinosus contracts,' and that the rectus femoris 

 simultaneously relaxes, if it be in a hypertonic condition (as a result 

 of decerebrate rigidity).* 



If the preparation is still in suitable condition, the experiment 

 should be terminated by exposing the lumbar portion of the spinal 

 cord and studying THE FUNCTIONS OF THE SPINAL ROOTS, noting also 

 the effect produced on the rigidity by their section. To expose the 

 roots, place the animal on its belly with a thick pad or block of wood 

 under the lower portion of the abdomen, and make an incision in 

 the mid line of the back over the spines of the lumbar vertebrae. 

 Separate the muscles from both sides of the spinous processes and 



*This experiment succeeds best on the decerebrate cat. If time is limited 

 the experiment should be omitted and that on the spinal roots performed. 



