538 ANIMAL PHYSIOLOGY. 
an interior or lower division (crusta), going mostly to the cor- 
pus striatum, and a posterior division (tegmentum), passing 
principally to the optic thalmi; many, possibly most of them, 
ultimately reach the cortex. Many clinical observers do not 
hesitate to speak of the optic thalamus as sensory, in function 
and the corpus striatum as motor; but the clinical and patho- 
Fic, 389,—Transverse section of human brain (after Dalton). This and the preceding figure 
are somewhat diagrammatic. 1, pons Varolii; 2, 2, crura cerebri ; 3, 3, internal capsule ; 
4, 4, corona radiata ; 5, optic thalamus ; 6, lenticular nucleus ; 7, corpus callosum. 
logical evidence is conflicting—all lesions of these parts not 
being followed by loss of sensation and motion respectively ; 
though an injury to the internal capsule generally results in 
paralysis. All are agreed that the symptoms are manifested 
on the side of the body opposite to the side of the lesion, so 
that a decussation must take place somewhere between the 
ganglion and the periphery of the body. 
There is no doubt that the optic thalamus, especially its 
posterior part, is concerned with vision, for injury to it is fol- 
lowed by a greater or less degree of disturbance ‘of this func- 
tion. As has been already pointed out, unilateral injury of 
either of these ganglia leads to inco-ordination or to forced 
movements. That these regions act some intermediate part in 
the transmission of impulses to and from the brain cortex, and 
that the anterior one is concerned with motor, and the pos- 
terior possibly with sensory (tactile, etc.), and certainly with 
visual impulses, may be stated with some confidence, though 
further details are not yet a subject of general agreement. 
