222 PHYSIOLOGY OF CENTRAL NERVOUS SYSTEM. 



observations upon dogs and monkeys in which the entire cere- 

 bellum or certain definite parts had been removed. He lays stress 

 upon the fact that the violent disturbance of movement is tem- 

 porary and is slowly recovered from in time. He was led, therefore, 

 to view these disturbances as due primarily not to the loss of the nor- 

 mal functional activity of the organ, but to irritations resulting from 

 the operation. When this stage of irritation is passed the real 

 defects which indicate the true function of the cerebellum become 

 apparent. These defects exhibit themselves as a loss of power 

 in the neuromuscular apparatus of the complex voluntary move- 

 ments, and he analyzes these results under three heads: First, 

 a loss of force in the muscular contractions, a condition of asthenia ; 

 second, a loss of tone in the muscles of the limbs and trunk, par- 

 ticularly in the hind limbs, a condition of atonia; and, third, a 

 loss of steadiness in the muscular contractions, a condition of 

 astasia. The astasia manifests itself in a tremor of the muscles 

 when voluntarily contracted, especially in movements requiring 

 much exertion. Luciani supposes that this tremor is due to an 

 alteration that is, a slowing of the rhythm of discharges of the 

 impulses from the motor centers. The functions of the cerebellum 

 on his theory are expressed, therefore, by saying that it is an aug- 

 menting organ for the activity of the neuromuscular apparatus ; and 

 that, so far as this augmenting or strengthening activity can be ana- 

 lyzed, it consists in an increase in the energy of the motor discharges 

 (sthenic action), an increase in the tension or tone of the motor 

 centers and their connected muscles (tonic action), and an increase 

 in the rhythm of the motor impulses (static action) so that nor- 

 mally the muscular contractions are of the nature of complete 

 -tetani. Luciani believes that this action of the cerebellum is 

 continuous, although varying in intensity, and that it affects all 

 of the musculature of the body, and not simply the muscles con- 

 cerned in body equilibrium. This constant motor activity is in 

 turn dependent upon a constant inflow of sensory impulses into 

 the cerebellum along its afferent connections, particularly upon the 

 impulses from the vestibular portion of the internal ear, and those 

 from the muscle sense fibers and perhaps also from the fibers of 

 the cutaneous senses. The constant augmenting activity of the 

 cerebellum is therefore a species of reflex effect, a reflex tonus 

 which affects all the musculature. Whether the cerebellar mechan- 

 ism is especially arranged to co-ordinate its effect upon the neuro- 

 muscular apparatus, that is, in some way to adapt the move- 

 ments to a definite end Luciani leaves an open question. He 

 does not believe that a lack of co-ordination (cerebellar ataxia) 

 is necessarily present in cerebellar lesions ; but admits that, if this 

 symptom is an invariable one, it would be necessary to add to 



