SEC. 2. AS A CENTRE OR GROUP OF CENTRES OF 

 AUTOMATIC ACTION. 



Irregular automatism, i.e. a spontaneity comparable to our own 

 volition, is wholly absent from the spinal cord. A brainless frog 

 placed in a condition of complete equilibrium in which no stimulus 

 is brought to bear on it protected from sudden passing changes in 

 temperature, from a too rapid evaporation and the like remains 

 perfectly motionless till it dies. Such apparently spontaneous 

 movements as are occasionally witnessed are so few and seldom, 

 that we can hardly do otherwise than attribute them to some 

 stimulus, internal or external, which has escaped observation. In 

 the mammal (dog) after division of the spinal cord in the dorsal 

 region regular and apparently spontaneous movements may be ob- 

 served in the parts governed by the lumbar cord. When the 

 animal has thoroughly recovered from the operation the hind limbs 

 rarely remain at rest for any long period ; they move restlessly in 

 various ways; and when the animal is suspended by the upper 

 part of the body, the pendent hind limbs are continually being 

 drawn up and let down again with a monotonous rhythmic regu- 

 larity, highly but perhaps falsely suggestive of automatic rhythmic 

 discharges from the central mechanisms of the cord. In the newly 

 born mammal too, after removal of the brain, apparently spon- 

 taneous movements are frequently observed. This greater prone- 

 ness to activity is however just what might be expected, when 

 we take into consideration the more rapid metabolic changes and 

 the consequent greater molecular mobility of the whole nervous 

 system of the mammal. The movements, even when most highly 

 developed, are wholly different from the movements irregular in 

 their occurrence, but orderly and purposeful in their character, 

 which result from the working of volition. 



382 



