224 PHYSIOLOGY OF CENTRAL NERVOUS SYSTEM. 



side. In man there are several cases on record in which the organ 

 was shown by autopsy to be largely or completely atrophied and 

 numerous cases of tumors affecting the cerebellum. In the latter 

 group of cases there may be certain marked subjective symptoms, 

 such as headache, and especially vertigo, and also a certain degree 

 of ataxia or awkwardness and uncertainty of movement. So also 

 in the cases of atrophy, in which probably the condition developed 

 slowly through a number of years, a degree of ataxia was exhibited, 

 especially when the movements were rapid and forced. In the 

 ataxic condition resulting from tabetic lesions of the posterior col- 

 umns the effect upon the movements is increased by covering up 

 the eyes (Romberg's symptom), the individual being then deprived 

 of his visual stimuli as well as those coming by way of the muscular 

 and cutaneous nerves. In cerebellar ataxia, however, the effect 

 is not increased by closure of the eyes, a result which is probably 

 explained by the fact that the individual still possesses his paths 

 of muscular and cutaneous sensibility to the cerebrum, and these 

 senses may be used in the reflex adjustments of voluntary move- 

 ments. 



Interpretation of the Experimental and Clinical Results. 

 Flourens was led by the striking results of his operations on pigeons 

 to suggest the view that the cerebellum is an organ for the co- 

 ordination of the movements of equilibrium and locomotion. 

 Objections were raised to this view. Some observers (Dalton, 

 Weir Mitchell) found that if the pigeons from which the cerebellum 

 had been removed w r ere kept long enough the effects first observed 

 gradually disappeared, so that finally the animals were able to 

 move or fly with no marked difference from the normal animal 

 except that fatigue was shown much more quickly. Hence the 

 view advocated by Mitchell that the essential function of the 

 cerebellum is that of an augmenting apparatus for the voluntary 

 movements. With regard, to this view it may be remarked in 

 passing that pigeons with the cerebral hemispheres removed exhibit 

 apparently as a permanent symptom the same tendency to rapid 

 fatigue after sustained muscular effort. By the same logical process 

 therefore one might conclude that one function of the cerebrum 

 is that of an augmenting organ to the motor discharges from the 

 cerebellum or midbrain. So also the cases of complete or nearly 

 complete atrophy of the cerebellum in human beings in which no 

 evil result followed other than a slight degree of cerebellar ataxia 

 have been used as an argument against the view that this organ 

 is necessary to the co-ordination of the complex voluntary move- 

 ments. The view that the cerebellum has essentially a direct 

 co-ordinating function has been criticized most seriously by Luciani. 

 This observer made a series of long-continued and most careful 



