Licence: Public Domain Mark
Credit: The nervous system and its conservation. Source: Wellcome Collection.
Provider: This material has been provided by the Augustus C. Long Health Sciences Library at Columbia University and Columbia University Libraries/Information Services, through the Medical Heritage Library. The original may be consulted at the the Augustus C. Long Health Sciences Library at Columbia University and Columbia University.
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![nicnts of certain processes in the cerebral j>;ray matter. We must assume that the streams of energy flashing from point to point in the cortex arc very numerous, and we cannot say why some are attended with corresponding phenomena in our consciousness while others are not. The problem of attention is suggested at once, and this belongs to the psychologist. For the physiologist it is a persistent mystery how the physical mechanism can be so multifarious and the su])jective experience so unified. The afferent fibers which have thus far been discussed are those originating below the head. These exert direct- ing influences upon the central mechanism which we are not likely to overestimate, but their contribution to the current of sensation is much less vivid and interesting than that furnished by way of the cranial nerves. If there is a partial exception to be conceded, it is in the case of the fingers, with their wonderful sensory equipment. Other- wise it needs no argument to prove the superior prominence of the eye and the ear in guiding intelligent conduct. To be without taste or smell would be a minor privation, but deafness and blindness are grave calamities, and when the two are conjoined we regard the victim with a pitying awe, which may be displaced by reverent admiration when we witness such triumphant emergences as those of Laura Bridgman and Helen Keller. Something has been said previously of the afferent service of the cranial nerves. It will ))e recalled that in these nerves there is no clear assorting of sensory fibers to form a series of dorsal roots. In two or three cases there are ganglia in which are gathered the perikarya which maintain the passing fibers. The largest of these ganglia and the one most frequently referred to is the Gasserian ganglion on the trunk of the great fifth (trigeminal) nerve. Vision.—The immense importance of the optic impulses in determining the content of the human mind and the conduct of human life is faithfully indicated in the large size of the optic nerves. Nearly half a million fibers are](https://iiif.wellcomecollection.org/image/b21206545_0084.jp2/full/800%2C/0/default.jpg)
