SYMPATHETIC NERVOUS SYSTEM. 147 



blindness of the corresponding halves of the two retinae. Destruction of 

 both occipital lobes in man results in total blindness. Stimulation or irri- 

 tation of the visual centre causes photopsia, or hallucinations of sight, in 

 corresponding halves of the retinae. There have been instances of injury of 

 these parts when sensations of color were abolished with preservation of 

 those of space and light, thus showing a special localization of the color 

 centre. Late experiments show that the centres of the two hemispheres are 

 united, as ocular fatigue of a non-used eye was proportional to the fatigue 

 of the exercised one. 



The Auditory Centres are located in the temporo-sphenoidal lobes. 

 Word deafness is associated with softening of these parts, and their complete 

 removal results in deafness. 



The Gustatory and Olfactory Centres are located in the uncinate gyrus, 

 on the inner side of the temporo-sphenoidal lobes. There does not seem to 

 be any differentiation, up to this time, of these two centres. 



The centre for tactile impressions was located by Ferrier in the hippo- 

 campal region. Horsley and Schafer found that destructive lesions of the 

 gyrus fornicatus was followed by hemianaesthesia of the opposite side of the 

 body, which was more or less marked and persistent. These observers 

 conclude that the limbic lobe " is largely, if not exclusively, concerned in the 

 appreciation of sensations painful and tactile." 



The Superior and Middle Frontal convolutions appear to be the seat of 

 the reason, intelligence and will. Destruction of these parts is fol- 

 lowed by proportional hebetude, without any impairment of sensation or 

 motion. 



SYMPATHETIC NERVOUS SYSTEM. 



The Sympathetic Nervous System consists of a chain of ganglia 

 connected together by longitudinal nerve filaments, situated on each side of 

 the spinal column, running from above downward. The two ganglionic 

 cords are connected together in the interior of the cranium by the ganglion 

 of Ribes, on the anterior communicating artery, and terminate in the gan- 

 glion impar, situated at the top of the coccyx. 



The chain of ganglia is divided into groups, and named according to the 

 location in which they are found, viz.: cranial, four in number ; cervical, 

 three; thoracic, twelve ; lumbar, five; sacral, five; coccygeal, one. Each 

 ganglion consists of a collection of vesicular nervous matter, bundles of 

 non-medullated nerve fibres, imbedded in a capsule of connective tissue. 



