viir THE HIND-BKAIN 465 



or voluntary reflexes of a compensatory character, capable of 

 replacing the body in the normal position of equilibrium, it is 

 obvious that equilibration of the body in space is not a specific 

 function, attributable to this or that part of the system, but a 

 complex function, dependent on the intimate organisation and 

 functional harmony of the system as a whole. 



The proof that cerebellar ataxy is not due to defective equi- 

 libration in space, but to the asthenic, atonic, and astatic neuro- 

 muscular state, is the fact that there is a period or stage of 

 cerebellar ataxy during which the animal is incapable of walking 

 or falls at every step, although it is still quite capable of floating 

 and swimming perfectly in the water where equilibration is 

 much more difficult without losing its equilibrium, and of 

 regaining it promptly if it is lost, and further of readily altering 

 its direction by appropriate compensatory acts in order to get 

 near the edge of the basin and climb out (Luciani). 



In order to discredit this observation, it was suggested that 

 " the movements required in swimming in water are not 

 necessarily so exact as those of walking " (Murri). Obviously the 

 everyday fact has been overlooked that every normal person 

 knows how to walk, while many have never learned to swim and 

 cannot keep themselves afloat in water without drowning. 



The publication of our Monograph, The Cerebellum (1891), had 

 an undoubted influence on Terrier. In reviewing our work 

 (Neurological Society of London, 1894) he no longer spoke of the 

 cerebellum as an organ of equilibration, nor as a collection of 

 unconscious centres of reflex action destined to come into play to 

 restore the equilibrium of the body as soon as it is menaced in 

 any given direction. He admitted, on the contrary, that the cere- 

 bellum exercises a constant influence (directly or through the 

 other cerebrospinal centres) upon the motor systems of the 

 animal machine, adding that " even, however, if we assume that 

 this is the true formula for the influence of the cerebellum it still 

 remains to be determined how its activity is called into play and 

 brought to bear on the muscles, either in association with the 

 cerebrum or independently." L 



In his earlier work Stefani applied Goltz' theory of the semi- 

 circular canals to the cerebellum, and maintained that " the cere- 

 bellum may be regarded as an organ which utilises the impulses 

 sent out from the semicircular canals to acquaint the animal 

 with the position of its head in relation to the environment." 

 The decerebellated animal is not able to keep its head in the 

 normal position because it has lost consciousness of its position. 

 When it wants to carry out some movement its head oscillates in 

 all directions and the centre of gravity is displaced to one or 

 the other side, while the animal reacts to these displacements by 



1 Ferrier, Brain, 1894, vol. xvii. p. 17. 

 VOL. Ill 2 H 



