A Reference handbook of the medical sciences embracing the entire range of scientific and practical medicine and allied science . e axis of the cylinder atsuch an angle as to increase the curvature in the planewhere it is smallest (or decrease it through the use ofplano-concave cylinders in the plane where it is greatest)to put the dioptric system into approximately perfectcondition. 2. ViSLWL —As the telescope or the cam-era must be provided with a directive apparatus bymeans of which the direction of its optical axis may bechanged, so the e3e is provided with an apparatus forchangin
A Reference handbook of the medical sciences embracing the entire range of scientific and practical medicine and allied science . e axis of the cylinder atsuch an angle as to increase the curvature in the planewhere it is smallest (or decrease it through the use ofplano-concave cylinders in the plane where it is greatest)to put the dioptric system into approximately perfectcondition. 2. ViSLWL —As the telescope or the cam-era must be provided with a directive apparatus bymeans of which the direction of its optical axis may bechanged, so the e3e is provided with an apparatus forchanging the direction of the line of vision. In directingthe vision from one point or object to another the axis ofthe eye is turned upward or downward, outward orinward, or is circumducted, in short, the axis of the eyehas an absolutely universal motion within its limits. 241 , REFERENCE HANDBOOK OF THE jMEDICAL SCIENCES. ((«) Monoculnr Fixation.—T\\ii term monocular fixationis used to designate tlie mecliauieal adjustment of tlieeye to bring the of the object upon tlie macula JnfertorOblique ^(s) ?. Fig. 3023.—DiaRram to Illustrate the Directions toward which the Optical Axis is Directed or In-clined by the ri>ntractii>u nf the Individual Muscles. MM is the median line; B, the right The lower part of the object being focussed upon theupper segment of the two , and the right part ofthe object being focussed ujjon the left part of the tworetrutc, that is upon the mediansegment of the right retina andthe external segment of the leftretina. It is evident that we have todeal with a complex mechanicalaction: (1) With double monocu-lar fixation, and (2) with converg-ence of the visual axes of the one refers to Wallers diagramhe can readily tabulate the mus-cles involved in directing the twoeyes in any particvilar in Fig. .5024 the object 0 movetoward the right eye along thevisual axis OSF the fixation ofthe right eye will not
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