548 PHYSIOLOGY CHAP. 



cerebral cortex, used the currents from the secondary coil of Du 

 Bois-Reymond's sliding inductorium, coupled with a Daniell cell, 

 and succeeded in localising more centres, and in extending the 

 excitable zone, in the dog (Fig. 275). This was a marked advance, 

 not only as regards specialisation of the reactions, but also as to 

 their form. Terrier's observations, in fact, bring out clearly that 

 the motor reactions evoked on faradisation of the cerebral surface 

 have a marked character of purpose, that is, they are perfectly 

 analogous to the various movements co-ordinated to a given end 

 which the animal voluntarily performs under normal conditions 

 of life. These are not obtained with galvanic currents, which 

 induce sudden contractions of given groups of muscles at each 



Fio. 2V5. Cortical motor centres of dog according to Ferrier. 1, opposite hind-limb advanced; 

 3, tail moved laterally ; 4, retraction and adduction of opposite hind-limb ; 5, protraction of 

 opposite fore-limb with elevation of shoiilder ; 7, closure of opposite eye, and movement of 

 eye-balls ; 8, retraction and elevation of opposite angle of mouth ; 9, opening of month and 

 movements of tongue ; 10, retraction of angle of mouth owing to contraction of platysma ; 

 11, elevation of angle of mouth and side of face, with closure of eye ; 12, opening of eyes with 

 dilatation of pupils and movements of eyes and head to opposite side ; 13, movement of eyes to 

 opposite side ; 14, pricking or sudden retraction of opposite ear ; 15, torsion of nostril on same 

 side ; 16, elevation of upper lip and dilatation of nostrils. 



opening and closure, which have not the perfect association and 

 succession characteristic of normal voluntary acts. 



Working with Tainburini (1878) we brought some new facts 

 to light, in regard both to specialisation of the reactions from the 

 various excitable areas in the dog, and to their extent and 

 location in different individuals and in both hemispheres in one 

 animal. It is not accurate to say that the excitable areas which 

 Hitzig termed centres have an approximately constant position 

 in different dogs, and it is a mistake to assume with Terrier that 

 they are symmetrical in the two hemispheres of the same animal. 

 Not only may the centres for the front limbs be grouped in two 

 distinct areas, capable of provoking two opposite reactions, but 

 a similar specialisation can more frequently be demonstrated also 

 in the region concerned with the movements of the hind-limb. 

 Lastly, not only does the excitability of the centres vary with the 



