634 Dynamic Theory. 



sense alone, the visual sense being in abeyance, and neither helping nor 

 counteracting, and yet the somnambulist will often transverse the most 

 perilous places with safety. The actions of hypnotic subjects are,under 

 the same guidance. In their case, hearing is not always cut off, but 

 vision usually is. Yet they will write whole pages with accuracy, going 

 over them to dot the i's and cross the t's. In this they are guided by 

 the muscular sense. 



The foregoing considerations in regard to the guiding sense, apply to 

 the actions that are made up in the optic thalamus and the corpora stri- 

 ata, considered as a single complete machine ; to the optic thalamus and 

 the sensory and motor organs of the cerebral cortex, considered as an- 

 other machine; and to the motor organs of the cerebrum in connection 

 with the sensory cells of the cortex, and their independent connection 

 with the external sense organs by way of the posterior one-third of the 

 internal capsule and the posterior layer of the crura cerebri, considered 

 as a third machine. For the idea formerly held, that all the sensory 

 paths to the cortex of the cerebrum were through the optic thalamus, 

 has been shown to be incorrect. The cortex possesses sensory connec- 

 tions with the periphery, independent of the optic thalamus, and motor 

 connections independent of the corpus striatum. Another idea formerly 

 maintained by some physiologists, was that the optic thalamus, with 

 perhaps the corpora quadrigemina, constituted the only centers of con- 

 scious sensation. Observations on the effects of disease and experi- 

 ment have shown this to be incorrect. (Ferrier. ) Without doubt the 

 cells of the cortex themselves are the seat of the sensations of the stim- 

 uli, the impact of which they receive, and, since the cerebral cortex is, 

 in man, by far the largest and most complicated collection of ganglions, 

 its importance as a center of consciousness, entirely eclipses all others. 

 But it does not follow there are no others, and if there are, the optic 

 thalami will certainly be included. The subject can, however, be dis- 

 cussed to better advantage further on. 



Corpora Striata. The ganglia of the corpora striata are motor, they 

 receive the afferent stimuli from the optic thalami, and send forth motor 

 stimulations, which traverse the anterior strands of the crura cerebri, 

 medulla oblongata and spinal cord, to the limbs, &c. It was formerly 

 thought that these ganglia were instruments under the control of the 

 cerebrum, and simply forwarded the motor results of the action of the 

 hemispheres. But this is now found to be incorrect. The fibres which 

 enter the corpora striata end there, and do not go on to the cerebrum at 

 all, so that these ganglia are probably in themselves independent ter- 

 minal centers, the same as the ganglia of the cerebrum. The motor 

 strands which pass down from the cortex of the cerebrum, to and through 

 the internal capsule, do not connect with the corpora striata, but go on 



