. Irish journal of medical science . cavity of the same shape,because this demands a change of form. The centre of motion is notonly at a distance from the anteri<jr, but also from the posterior pole ofthe eye ; its position is not very unfavourable. The researches which I made conjointly with Dr. Doyer, establish thatthe centre of motion is situated behind the centre of the optic axis, sothat the portion of this axis situated in front of the centre of notation isto that behind, as 15 : 11. {Vide the annexed table given from theFrench.) Tablk of the mean obtained by the examination of 19 em
. Irish journal of medical science . cavity of the same shape,because this demands a change of form. The centre of motion is notonly at a distance from the anteri<jr, but also from the posterior pole ofthe eye ; its position is not very unfavourable. The researches which I made conjointly with Dr. Doyer, establish thatthe centre of motion is situated behind the centre of the optic axis, sothat the portion of this axis situated in front of the centre of notation isto that behind, as 15 : 11. {Vide the annexed table given from theFrench.) Tablk of the mean obtained by the examination of 19 emmetropic myopic eyes, M = 1 : IG up to M = 1 : 2*25 12 emmetropic eyes, H=l:10 „ H=l: 375 Mean leng h of the *Tisual axis Situation of centre of motion BeUiud thticuruea lu front ou theI pobtirior ; of the sclerotic Proportiouper cent Hehiiid the middle of the viHual asiA Millimetres Millimbtres Millimetres EMH 23-53 13 54 9-99 = 57-54 42-46 1-77 25-55 14 52 : 11-03 =• 56-83 4317 1-75 22-10 13 22 : S-88 ^= 59-S 40-2 2-17. About the same proportions, however, were also found in the case of thelonger axes of myopic people; here, consequently, the centre of motionlies further away from the posterior surface of the sclerotic. Theexcursions are therefore, in these cases, for equal degrees of rotationlarger, and the movements necessarily limited; this limitation would bestill greater were not the entrance of the optic nerve, on account of thedisproportionate extension of the external posterior portion of the seg-ment, moved further inwards, and thus removed considerably less fromthe centre of motion. To this limitation, moreover, the greater distancebetween the centre of motion and the insertion of the muscles may helpto contribute, to which distance, the arc of rotation, obtained with agiven shortening of the muscles, stands in inverse proportion. Apart from the consideration of all this, the elongation of the axis ofthe eye gives of itself a sufficient explanation of th
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