ii6 BRAINS OF RATS AND MEN 



activities (for summary see Kappers, 1921, pp. 1090- 

 1092) and feeding movements (Dresel, 1924), but 

 its chief activities center about control of the skeletal 

 muscles, their tonicity, steadiness, and co-ordinated 

 action in mass reflexes (Wilson, 191 2; Vogt, 1920). 



In all mammals the globus pallidus retains its 

 ancestral character with but little change. In lower 

 mammals the olfacto-striatum and amygdaloid com- 

 plexes have as highly developed olfactory components 

 as in any reptiles — perhaps more so — and there is 

 great increase in the number and complexity of their 

 thalamic connections. The hypopallium is structural- 

 ly reduced, and its functions seem to have been in 

 part taken over by the rapidly expanding cortex. 



In marsupials, unlike higher mammals, the corpus 

 striatum is electrically excitable (Rogers, 1924). 

 There is also motor cortex far forward in the cerebral 

 hemispheres and an incompletely developed pyram- 

 idal tract (for head and fore limb control only) 

 extending to the upper level of the spinal cord. 

 Cortical control of head and fore-limb movements is 

 very incomplete, and destruction of the motor cortex 

 gives slight and transient motor disturbances of only 

 the finer arm movements. Destruction of both motor 

 cortex and underlying striatum gives in addition to 

 phasic disorders of movement, spastic contraction of 

 the fingers, tonic twisting of the neck toward the 

 operated side, and other symptoms of the striatal 

 syndrome. These observations again illustrate the 



