432 Anatomy Applied to Medicine and Surge? y. 



way, however, in which tumors of either the thalamus or 

 the corpus striatum may cause serious trouble is depend- 

 ent on their relationship to the internal capsule, hence a 

 tumor of these bodies would have to be strictly limited to 

 them alone, as otherwise is would produce symptoms from 

 pressure on the internal capsule. 



A tumor of the corpora quadrigemina causes, as a rule, 

 a staggering gait like that of a drunken person, and inter- 

 ference with certain automatic movements of the eyes, 

 such as in following a light with the eyes, etc., hence, irri- 

 tation of these bodies may cause nystagmus or involun- 

 tary movement of the eye from side to side. There is, 

 therefore, in this lesion more or less ophthalmoplegia, or 

 paralysis of most of the muscles of the eye, chiefly because 

 the oculo-motor nuclei are situated here, i.e., beneath the 

 Sylvian aqueduct. In addition, there is some disturbance 

 of hearing since the central tract for the cochlear nerve 

 ascends through the corpora quadrigemina to the internal 

 capsule. 



A tumor of the crus cerebri (Fig. 13) may produce 

 paralysis of the opposite side of the face and body, since 

 the motor fibres for these regions lie in the middle two- 

 fourths of the crusta. When the tumor involves the lower 

 part of the crus, there is, in addition, paralysis of the third 

 nerve on the same side as the lesion from direct pressure 

 on this nucleus, which is situated in this portion of the 

 crus. 



Pans Variolii. The cranial tracts from the cortex for 

 the facial nerve decussate about the middle of the pons, 

 whereas the pyramidal tract or motor fibres for the limbs 

 passes downwards to decussate in the medulla, hence a 

 lesion in the pons will produce symptoms that differ in ac- 

 cordance with its situation. Thus, in a tumor of the up- 



