Sensory and Motor Tracts in Encephalon. 17 



The oculo motor may be paralyzed on the same side, but the face 

 and tongue on the opposite side, owing to the fibres crossing in 

 the pons. There may be turning movements. 



The Optic Thalamus transmits sensory currents to the cere- 

 bral cortex. Lesions in this organ cause sensor}^ paralysis on the 

 opposite side of the body. Afferent currents that do not traverse 

 the thalamus cause reflexes only. It contains one of the roots of 

 the optic nerve and its destruction will impair vision. Its in- 

 juries ma}- also produce turning movements. 



The Corpus Striatum transmits motor currents originating 

 in the cerebral cortex. Lesions of its interior (lenticular nucleus) 

 cause motor paralysis and .sometimes anae-sthesia on the opposite 

 side of the body. Electrical stimulation of this nucleus causes 

 general mu.scular contractions of the opposite side of the body. 

 Irritation of the surface layers is painless and symptomless. 



The Cerebellum has been long credited with coordination, 

 and Flourens, after its removal from a pigeon, found an utter lack 

 of harmonized movement in walking, springing or balancing. 

 Luciani removed the organ from a bitch and, after full healing of 

 the part, found a lack of nmscular tone (a cerebellar ataxy), .so 

 that no great muscular effort could be satisfactorily accompli.shed. 

 After months, marasmus set in and proved fatal. The lack of 

 coordination is especially connected with lesions of the vermiform 

 process, those of the posterior portion causing falling forward and 

 those of the anterior portion, falling backward. Injury to the 

 middle peduncle on one side causes turning or rolling to the 

 opposite side. Under slighter injuries there may be only un- 

 steadiness and staggering like a drunken man. Nausea and 

 vomiting, with more or less stiffness of the neck or oposthotonos, 

 may be present. Rolling of the eyes or squinting may occur. 



Focal Cortical Centers of the Cerebrum. Cortical 

 Localization. Much has been done experimentall}^ and by 

 observation of morbid lesions to locate functions in the different 

 convolutions, and though the .subsidiary implication of adjacent 

 and interdependent parts interferes with a perfectly confident 

 diagnosis, yet certain fundamental facts may be borne in mind as 

 contributing to a satisfactory diagnosis. 



Arloing, on the basis of his own experiments and those of his 



