THE CEREBELLUM 209 



man the finer, more conscious movements of the body are 

 controlled directly from the cerebrum, while the subconscious 

 or dimly conscious movements of locomotion and equilibrium 

 are regulated through the cerebellar centres." 



The first effect of removal of the cerebellum in a dog is a 

 rigidity and tonic spasm of certain muscles. Later all the mus- 

 cles of the body, especially those of the hind limbs and those 

 which fix the head, lose their tone and contract with a peculiar 

 want of steadiness. When one lateral half of the cerebellum is 

 removed the muscles on the same side only are affected. In 

 man extensive lesions of the cerebellum are accompanied by a 

 marked inability to maintain an upright position, by giddiness, 

 nystagmus, and tremor on attempting voluntary movements. 

 In the ataxic condition from tabetic lesions the effect upon 

 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 the closure of the eyes, since the individual 

 still possesses his paths of muscular and cutaneous sensibility. 

 Cerebellar lesions give no sensory or voluntary paralysis, nor 

 is there any psychical disturbance. 



A striking symptom of cerebellar lesions are the so-called 

 forced movements. They are not absolutely diagnostic, however, 

 since they follow many unilateral injuries of the brain, e. g., 

 to the pons, crus cerebri, posterior corpora quadrigemina, 

 corpus striatum, and cerebral cortex. These movements are 

 movements toward the side of the lesion apparently beyond 

 voluntary control. They are precisely like those following 

 injuries to the semicircular canals. They may consist of a rota- 

 tion around a longitudinal axis, or the animal may run around 

 and around in a circle (circus movements) ; or, with the tip of 

 its tail as a centre and its body as a radius, it may describe a 

 circle; or, it may rush forward, turning innumerable somersaults. 

 In man, forced movements associated with vertigo have been 

 observed in tumor of the middle peduncles. 



The connections of the cerebellum with other portions of 

 the central nervous system are significant in considering its 

 functions. These connections may be grouped under three 

 heads : 

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