236 PHYSIOLOGY OF CENTRAL NERVOUS SYSTEM. 



moved the animal shows a most distressing inabiUty to stand or 

 move. There seems to be no muscular paralysis, but, at first, 

 a total lack of power to co-ordinate properly the contractions of the 

 various muscles involved in maintaining equilibrium. The animal 

 takes a most abnormal position, with the head retracted and 

 twisted, and any attempt to move is followed by violent disorderly 

 contractions that may result in a series of involuntary somersaults. 

 The animal is totally unable to fly. When the injury to the cere- 

 bellum is less the effect upon the movements is either too slight 

 to be noticed or is shown in a greater or less uncertainty in its 

 movements. When it attempts to wallc, for instance, it exhibits 

 a staggering, drunken gait, a condition designated as cerebellar 

 ataxia. Similar operations on mammals give in general the same 

 results. If the operation is unilateral, — that is, affects only one 

 hemisphere, — the animal (dog) exhibits forced movements, such 

 as a tendency to roll around the long axis of his body toward the 

 iniured side and subsequently movements in a circle toward the same 

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

 organ was shown by autopsy to be largely or completely atro- 

 phied, and numerous cases of tumors affecting the cerebellum 

 have also been reported. In the latter group of cases there 

 may be certain marked subjective symptoms, such as headache, 

 and especially vertigo, but on the objective side the neurologists 

 emphasize the fact that in cerebellar disorders the lack of accurate 

 co-ordination or asynergy is the fundamental symptom. This 

 condition may be manifested by an ataxic gait, by muscular 

 tremors, and, especially, by lack of skill in performing certain 

 definite movements which require the associated activity of several 

 muscles — for example, the placing of the finger to the nose or 

 the rapid alternation in the contraction of antagonistic muscles, 

 abduction and adduction, or pronation and supination.* So 

 also in the cases of atrophy, in which probably the condition devel- 

 ops slowly through a number of years, a degree of ataxia is ex- 

 hibited, especially when the movements are rapid and forced. 

 In the ataxic condition resulting from tabetic lesions of the 

 posterior funiculi 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 movements. 



* Mills and Weisenburg, Journal of the American Medical Association," 

 November 21, 1914. 



