The Cerebrum. 431 



blindness, is, as a rule, limited to tumors involving the left 

 hemisphere in right-handed persons (or the right hemi- 

 sphere in the left-handed), possibly because, that in right- 

 handed persons, the left half of the brain is slightly better 

 differentiated, especially the motor part, as shown by the 

 more common use of the right hand. 



The corpus callosum is a great commissure connect- 

 ing identical parts of the two hemispheres together, yet 

 the conclusion of Erb and Ferrier is, that almost the entire 

 corpus callosum may be destroyed without producing dis- 

 turbance of motion or co-ordination, or of sensation, gen- 

 eral or special, and without any disturbance of intelli- 

 gence. Tumors of the corpus striatum produce no symp- 

 toms of themselves. Mills considers that both the optic thal- 

 amus and the corpus striatum preside over the higher auto- 

 matic acts such as the gait, emotional control, etc., and 

 hence, if diseased, volitional acts may replace these auto- 

 matic ones so that no apparent ill effects will result from 

 their involvement. Ferrier states that lesions of a stationary 

 character may be found in the grey matter of the corpus 

 striatum without any manifestation of motor symptoms. 

 Several observers, however, have noted a condition of 

 pseudo-bulbar paralysis as present when the lesion was 

 situated in the lenticular nucleus. 



Optic thalamus. The symptoms of a tumor involv- 

 ing the thalamus are nearly as obscure as in the case of 

 the corpus striatum vision, however, has been found im- 

 paired in some cases, although, more often, not, and hemi- 

 anaesthesia has been occasionally present (likely due to 

 pressure on the posterior limb of the capsule) . It is said 

 that paralysis of mimetic movements of the face and the 

 occurrence of post-hemiplegic choreic disorders are in 

 favor of a lesion implicating the opposite thalamus. One 



