Relations between the Cerebellar and other Centres, tyc. 21 



the current was applied, and that on the latter being shut off the 

 tonus was immediately re-established. 



As this observation appeared to indicate a distinct relation between 

 the cerebellum and the bulbospinal system of lower centres, it was 

 obviously very important to examine it further, especially as to 

 whether it was a truly central effect or not. 



It was soon made clear that the effect was a constant one, pro- 

 vided that the above mentioned tonus was distinctly established, and 

 further that the primary effect of excitation of the cerebellum upon 

 the upper limb in such case was not an active relaxation of the triceps 

 alone, but that there was a marked contraction of the biceps. 



Further, this effect, though constant, when tonus is present, was 

 not the character of the muscle changes obtained when the tonus 

 was absent. 



It was, therefore, necessary to arrange a large series of experi- 

 ments to determine a comparison between the changes in the two 

 groups of muscles according as to whether the cortex cerebri, corona 

 radiata, crusta, tegmentum, cerebellum, or cerebellar peduncles were 

 excited either singly or in combination. 



After making fifteen experiments in which the contraction of the 

 muscles involved was determined by inspection, passive movement 

 and palpation only, the movements produced were graphically re- 

 corded, and the general conduct of the experiments arranged as 

 follows : — 



Method of Experimentation. 



The animal (the dog and cat have so far been examined) was 

 anaesthetised by ether, tracheotomy performed for the purposes of 

 convenient anaesthesia and a ligature looped loosely round each com- 

 mon carotid artery. The left sigmoid gyrus, the right occipital lobe 

 and right half of the cerebellum were freely exposed, the dura mater 

 preserved intact, and the whole kept warm by pads of absorbent 

 wool soaked in warm normal saline solution. 



The right forearm was next carefully detached at the elbow after 

 the brachial artery had been ligatured, the nerve trunks cut short, 

 and the lower bony insertions of the biceps and brachialis anticus 

 separated from the ulna and radius shafts. A ligature was then 

 attached to these conjointly, and a similar ligature was fastened 

 to the olecranon, which had been detached by a cut through the 

 bottom of the greater sigmoid notch. 



The threads securing the muscles were affixed to Fick's spring 

 myographs of suitable strength, and a record thus obtained on paper 

 of the changes in form of the muscles, as well as of the moment and 

 duration of excitation by suitable signals (F. J. Smith's). 



The nerve centres were excited in all cases by fine platinum elec- 



