558 PHYSIOLOGY CHAP. 



and Beevor in "Six (1890), and by Bechterew in three adolescents 

 suffering from idiopathic epilepsy (1899). 



.The general conclusions arrived at by Bechterew, from the 

 results of his predecessors as well as of his own researches, are as 

 follows : 



(a) The general arrangement of the motor centres in man 

 coincides approximately with that observed in the lower apes 

 (Macacus, Cercopitliecus). In fact, according to Bechterew, they 

 include both the central or Eolandic convolutions, besides the 

 adjacent regions of the frontal convolutions. 



(6) The centres for the lower limbs He in the upper segment of 

 the postcentral convolution ; the centres for the upper limbs lie in 

 the median segment of the two central convolutions ; immediately 

 below these are the centres for the thumb and fingers, and finally 

 the centres for the face lie in the lowest segment of the two central 

 convolutions. 



(c) The centres for the lateral movements of the head and eyes 

 correspond, as in the monkey, with the posterior segment of the 

 second frontal and probably extend to the adjacent regions 

 as welL 



(d) The centres for the musculature of the back lie on the 

 surface of the precentral convolution, above the centres for the 

 upper limb/and probably extend, as in the monkey, to the adjacent 

 mesial surface of the hemisphere. 



(e) In man, as in the monkey, there are special centres for the 

 thumb and fingers, which lie immediately below the motor centres 

 for the upper limbs. 



(/) As in monkeys, the several cortical centres above 

 enumerated are separated in man by tracts of inexcitable cortex 

 (Bechterew). 



This last observation merely echoes the results obtained by 

 Beevor and Horsley on the oraug, which were contradicted by the 

 later and more numerous experiments of Griinbaum and Sherrington 

 on various species of anthropoid apes. The supposed isolation of 

 centres noted by these authors probably depends upon a depression 

 of the normal excitability of the cortex, due either to excessive 

 narcosis or to the prolonged exposure of the cerebral surface, 

 owing to which only the focal areas of the different centres remain 

 excitable, while the peripheral borders, by means of which these 

 centres are connected and partially overlap, have completely lost 

 their excitability. Sherrington's observation that the anterior 

 limit of the excitable zone of the anthropoid apes is indefinite, and 

 becomes displaced backwards towards the central sulcus as the 

 cortical excitability is lowered, is in favour of this hypothesis. 

 In this class of research a positive result is invariably more 

 valuable than a negative result. 



An important correction of Bechterew's conclusions is offered by 



