532 SUTHERLAND SIMPSON 



the cerebrum increases the violence of the muscular symptoms. These 

 must, therefore, be due to action on the lower neurons. Following trans- 

 section of tte spinal cord, in the dog, at the level of the first lumbar verte- 

 bra, and at the same time thyroparathyroidectomy, it was found that, while 

 the'tremors and jerkings persist in the muscles supplied by nerves from 

 the division of the cOrd which is below the section, but is cut off from the 

 influence of the cerebrum and cerebellum, the sustained tonus in these 



Fig. 6. Simultaneous record of the tremors in the fore- and hind-leg of a dog, with 

 complete section of the spinal cord, to show independence of the rhythms. Time in 

 0.1 sec. (Noel Paton, Findlay, and Watson.) 



muscles is abolished. This is shown in Fig. 5 which represents tracings 

 taken simultaneously from fore and hind limbs. It was also found that 

 movements of the hind limbs, after cord section, were entirely independent 

 of the condition of the fore part of the body (Fig. 6). These investigators 

 believed that the tremors and jerkings are due to the condition of the spinal 

 cord and not dependent on the cerebrum or cerebellum, and are caused by 

 an action on the efferent, rather than the afferent neuron in the reflex arc. 

 The integrity of the cerebellar arc is essential for the sustained finer spas- 

 tic movements. In advanced cases both the cerebrum and cerebellum may 

 be involved secondarily. 



