THE NERVOUS SYSTEM AND CONSCIOUSNESS. 749 



As to the functions, in detail, of the optic thalami and the corpora 

 striata, hardly anything is known. It will be remembered that these 

 bodies are the rather large masses situated in the chambers of the cere- 

 bral hemispheres. There is no reasonable doubt, however, that they 

 are concerned with sensations and motions ; the thalami having to do 

 with impressions which are the physical antecedents of sensations, and 

 the striata with the execution of movements. This conclusion is con- 

 firmed by pathology. Disease of the striatum is followed by paralysis 

 on the opposite side of the body. Disease of the thalamus, while not 

 always so uniform in its testimony, does still, sometimes, give striking 

 evidence of a sensory significance of the organ. It should be distinctly 

 borne in mind, when speaking of these bodies, that paralysis of sensa- 

 tion and of voluntary motion may be produced by lesions in the cell- 

 matter of the cerebrum apart from any injury to the thalamus and 

 striatum ; it should also be remembered that destruction of these basal 

 ganglia breaks the connection between the cell-matter of the cerebrum 

 and the surface of the body, so that the cerebral hemispheres can not 

 perform their functions. It may, therefore, be true, as many maintain, 

 that these organs are not at all directly associated with consciousness, 

 their function being to adjust the connections of sensory and motor 

 fibers with the cerebrum. This general conclusion need not be taken 

 as supporting the fanciful opinions of Luys. Luys believes that in the 

 thalami sensorial impressions " are for the first time condensed, stored 

 up, and elaborated by the individual action of the elements that they 

 disturb in their passage. It is thence that they are launched forth into 

 the different regions of the cortical periphery (cell-matter of the cere- 

 brum) in a new form, intellectualized in some way to serve as exciting 

 materials for the activity of the cells of the cortical substance." Ac- 

 cording to the same writer, the striata do for our volitions the exact 

 reverse of that which is done by the thalami for our sensory impres- 

 sions. " It is in the midst of the tissues of the striata that the influ- 

 ence of volition is first received at the moment when it emerges from 

 the psycho-motor centers of the cerebral cortex. There it makes its 

 first halt in its descending evolution and enters into a more intimate 

 relation with the organic substratum destined to produce its external 

 manifestations — in one word, materializes itself." There can be no 

 doubt about the justice of describing this conclusion as fanciful and 

 quite beyond the data. 



We have outlined the structure of the cerebro-spinal system, and 

 have stated what may fairly be set down as established concerning the 

 functions of this system up to the cerebral hemisj)heres. With respect 

 to the presence of consciousness in the parts already examined, it is 

 plain that opinions radically differ. Some maintain that consciousness 

 is not manifested apart from the action of the cerebrum, that all nerve- 

 activities below this organ are reflex, their only distinctions being in 

 the matter of complexity. Others are equally positive that conscious- 



