636 Dynamic Theory. 



pus striatum alone may be recovered from, and no doubt the entire cor- 

 pus striatum might be gradually removed by disease, and its functions 

 assumed by the cortex without serious results. One-sided destruction 

 of the corpora striata has more striking apparent effect on the lower an- 

 imals than where both sides are affected alike. In the case of a rabbit, 

 both of whose lenticular nuclei have been destroyed, the animal is not 

 distorted or pulled out of shape, as where one side only is affected, but 

 it will sit motionless and apparently apathetic. It can still leap and 

 move in obedience to reflex irritation, but appears to have lost volitional 

 control of its limbs; and this may happen while the cerebral cortex is 

 entire, and it still possesses intelligence and desire. The animal might 

 recover from this, however, although the corpora striata are of more 

 relative value to the rabbit, whose smooth hemispheres have less relative 

 influence, than to the higher mammals. If the corpora striata of both 

 sides are removed, together with the front of the cerebrum, the animal 

 stands in a stupor, quite bereft of ability or inclination to move of it- 

 self. If the internal capsules, which contain the sensory and motor 

 tracts between the cortex and periphery, are destroyed, together with 

 the corpora striata, the paralysis is permanent, and no recovery of vol- 

 untary motion is possible. The nucleus lenticularis is the larger and 

 more important portion of the corpus striatum. The fibres from the 

 nucleus caudatus pass through it, and injuries to it are more permanent 

 in their effects than those to the nucleus caudatus. 



It appears, on the whole, that the basal ganglia constitute a complete 

 machine competent to run certain departments of the nervous economy 

 independently of the cortex of the cerebrum. We have seen that the 

 spinal cord, with its nerve fibres and ganglions of vesicular matter, 

 forms a machine competent to turn a simple tactile impression into a 

 muscular contraction. Its reactions are limited to those called reflex, 

 and the impressions of sound, light, &c. , do not enter into its combina- 

 tions and co-ordinations. Next, the medulla oblongata appears of it- 

 self to be another such machine, and the cerebellum is a third. These 

 two receive and combine a greater number of sensory impressions than 

 the cord, and convert them into much more varied motor stimulations, 

 giving rise to complicated, co-operative, muscular adjustments and move- 

 ments. The basal ganglia constitute the fourth of these machines, and 

 is of a higher grade than the others, because it is moved by a greater 

 number and variety of stimulations, not only from the tactile and mus- 

 cular senses, but from sight and hearing as well. Moreover, it is highly 

 probable that a certain limited degree of memory enters into the com- 

 binations which make up the motor stimuli generated in the corpus stri- 

 atum. 



There is still another center, the cerebrum, in whose combinations 



