vni THE HIND-BRAIN 445 



trunk, which might cause them to fall when the hands are used 

 for eating, by resting the head firmly on the ground or against 

 a wall. 



But these artifices, which the monkey can use in consequence 

 of the higher development of its motor centres, do not obscure the 

 signs of cerebellar deficiency, which are even more striking than 

 in the dog. 



The asthenia of the limbs on the injured side is expressed, in 

 addition to the signs already described in dogs, in the less use 

 which the animal makes of them ; when a favourite fruit is offered, 

 the monkey always grasps it with the hand of the sound side. 



This is not due to paresis of the limbs of the operated side, for 

 when the animal is suspended in the air by a sling round its 

 trunk, and one of the feet is brought near a small table, the latter 

 is strongly grasped with both hands. By pulling gradually on a 

 dynamometer which is fixed to the sling, while the ape is fastened 

 in this way to the leg of the table, it is possible to measure the 

 force by which the animal holds the table ; also it will be noticed 

 that first the hand of the operated side and then that of the sound 

 side gives way. 



The atonia is shown by the fact that when the monkey is on all 

 fours on the ground, in the horizontal position, the affected side 

 hangs lower, owing to the defective tone in the muscles of the 

 limbs on that side. Sometimes there is slight ptosis of the upper 

 eyelid of the injured side, and a drawing over of the mouth towards 

 the healthy side, when the animal shows its teeth in biting its 

 food. 



Finally, the astasia that is expressed in tremor, titubation, and 

 rhythmical oscillation is more marked in the monkey than in the 

 dog. Monkeys show tremor not only of the head, but unmistak- 

 ably in both the fore- and the hind-limb of the operated side, 

 whenever these are employed. 



Patrizi (1904), to render the atonia, asthenia, and astasia more 

 distinct, recorded graphically both simple twitches and tetanic 

 contractions of the muscles of the normal and the operated side 

 in dogs, after removal of one-half of the cerebellum. His observa- 

 tions show that muscles deprived of the influence of the cerebellum, 

 and excited, directly or reflexly, with electrical stimuli, in an 

 animal that has been immobilised but not anaesthetised, present 

 curves which differ from those of the normal side, owing to 

 diminution of tone, lower functional energy, more rapid fatigue, 

 and the incomplete fusion of the elementary twitches from which 

 the contraction as a whole results. 



On anaesthetising the animal to eliminate the normal tone of 

 the muscles the myograms of the limbs on the healthy side 

 resemble those obtained without narcosis from the limbs of the 

 decerebellated side. From these results Patrizi was led to con- 



