Page:Mind (Old Series) Volume 9.djvu/106

 94 G. STANLEY HALL AND E. M. HAETWELL. extirpated, the eyes often cease to rotate, then to accommodate, then to wink together. If one eye be covered, the other pupil expands to nearly twice its former size, or else the room grows dark ; if a bright image be impressed on one eye, and then it be closed and the other opened under suitable conditions, the after- image sometimes appears in normal projection. The comparative reaction-time for each eye ; the physiology of reading mirror- script, or writing after the early Greek fashion, alternately right and left; which eye is most often and soonest affected in the disparate moments of drunkenness and in strabismus ; whether lateral hemiopia is more common or complete on the right or left ; in which direction rotation soonest produces optical dizziness ; the number of fibres crossing each way in the optic chiasma ; these and many other points, including the ontogenetic and phylogenetic growth of the visual function generally from its dawn in animal life, must, we think, be much better understood before we can accept even Helmholtz's conclusion as to whether or how far it is a psychic act to join the activities of the two retinae, or explain the hypnotic colour-blindness or accommodation-cramp of one eye, the other remaining normal, or the binocular functions gene- rally ; and even then, we are convinced, the entire problem of bilateral symmetry and function of the other double organs of the body must be brought into relation with them before such ques- tions as these can be cleared up. Each must shed light on all, and all on each, and the study must be made comparative, to include the lower animals. The other senses offer less data. It has, however, been stated that the left helix is apt to be less perfectly developed, lower, more prominent, further from the eye ; that the left ear has less auditory power and greater liability to certain diseases ; that in conflicting or contrasting sounds, the impression made on the right auditory nerve is more likely to prevail ; and that one ear sometimes hears the same tone higher than the other. Even taste and smell, according to Valentin, present phenomena analogous to rivalry between their two lateral moieties when different tastes or odours are simultaneously applied to each ; but there was no differentiation, no record of preference for right or left. Of the dermal and muscular senses, there are many illustra- tions of the Shakespearean line, that " The hand of little employ- ment hath the daintier sense". Weber observed that things lifted with the left hand seemed heavier, and that sensory discri- minations (especially tactile, but perhaps not thermal, we should say) were finer on the left side of the body, which Wundt and others have spoken of as passive and sensory, while the right is called the active motor side. If a plate of metal, or a mustard plaster, be laid on the insensible side of an hysterical hemianaesthesic sub- ject, sensibility is more or less completely restored in a few minutes, and often for many hours, at the point of applications,