350 INNERVATION. [CHAP. XI. 



The results which experiments have yielded, add little that is 

 positive to our knowledge of the functions of these bodies. Flourens 

 found that neither pricking nor cutting away the optic thalami by 

 successive slices, occasioned any muscular agitation, nor did it even 

 induce contraction of the pupils. Longet found that removal of 

 one optic thalamus in the rabbit was followed by paralysis on the 

 opposite side of the body. It appears, however, that this was 

 done after the removal of the hemisphere and corpus striatum, 

 whereby the experiment was so complicated as to invalidate any 

 conclusion that might be drawn from it respecting the function of 

 the thalamus. Indeed, vivisections upon so complex an organ as 

 the brain are ill-calculated to lead to useful or satisfactory results ; 

 but we do not hesitate to quote such as have been made, from the 

 imperfect negative information which they afford. 



Nothing definitive respecting the proper office of the thalami can 

 be obtained from pathological anatomy. Extensive disease of these 

 bodies is attended with the same phenomena during life, as lesion 

 of similar kind in the corpora striata. Hemiplegic paralysis 

 accompanies both ; nor does it appear, that sensation is impaired 

 when the thalamus is diseased, more than when the corpus striatum 

 is affected. 



We see nothing in the phenomena which attend morbid states of 

 the thalami, to oppose the conclusion which their anatomical re- 

 lations indicate, namely, that they form a principal part of the 

 centre of sensation. The intimate connexion between the striated 

 bodies and the thalami, sufficiently explain the paralysis of motion 

 which follows disease of the latter; whilst, as the thalami do not 

 constitute the whole centre of sensation, but only a part, it cannot 

 be expected that lesion of this part would destroy sensation, so long 

 as the remainder of the centre on the same side, as well as that of 

 the opposite side, retain their integrity. Complete paralysis of sen- 

 sation on one side is very rare in diseased brain : a slight impair- 

 ment of it frequently exists in the early periods of cerebral lesion, 

 apparently as an effect of shock ; for it quickly subsides, although 

 the motor power may never return. 



According to the views above expressed, the corpora striata 

 and optic thalami bear to each other a relation analogous to that 

 of the anterior to the posterior horn of the spinal gray matter. 

 The corpora striata and anterior horns are centres of motion ; the 

 optic thalami and posterior horns, centres of sensation. The an- 

 terior pyramids connect the former; the olivary columns, and 

 perhaps some fibres of the anterior pyramids, the latter. The 



