FUNCTIONS OF THE INTERNAL CAPSULE 



567 



f the face, this power being lost in certain pathologic conditions. The 

 |<power of regulating the temperature of the body has been also assigned to 

 ;he thalamus, as destruction of its anterior extremity is usually followed by 

 i rise in temperature. 



The Internal Capsule. The internal capsule has been shown by the 

 results both of experiment and of pathologic processes to be, first, a pathway 

 for the transmission of nerve impulses from the cerebral cortex to the pons, 

 medulla, and spinal cord, which give rise to contraction of the muscles of the 

 opposite side of the body; and, second, a pathway for the transmission of 

 nerve impulses coming from skin, mucous membrane, muscles, and special 

 sense-organs to the cortex, where they give rise to sensations general and 

 special. It is therefore the common motor and sensor pathway. For the 



(Elb),s 0*H (DIG.), ABDO^N (Abd) H* K NEE (Kn.), D.orrs o* Fool 

 (Dig.). S. Sensor tract. O. T. Optic tract. A.T. Auditory tract. 



reason that it transmits both motor and sensor impulses, and for the further 

 reason that it is frequently the seat of pathologic lesions which are followed 

 by either a loss of motion or sensation or both, the internal capsule is one 

 of the most interesting parts of the central nerve system As shown m Fig 

 243 , it consists of two segments or limbs united at an obtuse ange, the knee 

 or elbow, which is directed toward the median line. The motor tea. 

 confined to the posterior one-third of the anterior ^g^.^^* 6 ,^ 

 two-thirds of the posterior segment. The sensor tract is confined to the 

 posterior one-third of the posterior segment, the extreme end of whi 

 contains the optic and auditory tracts. contains 



The region of the anterior segment in front of the motor tract 

 the fibersTthefronto-cerebellar tract, the function of which is unknown, 

 region contains fibers which descend from the cerebral cortex 



