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ble 
different muscles. It is likewise the question, whether the eye will really 
rotate round a constant axis, as in reality the position of the eye 
does not only depend upon the strength of the contracting muscle, 
but also upon the elasticity and resistance of the different surround- 
ing tissues. 
If we disregard these inaccuracies, the data supplied formerly 
will enable us to make a conception of the way that the line of 
vision follows during an isolated contraction of the m. oblig. sup. 
An inward rotation and deorsumduction will prevail; the abduction 
will be only insignificant, but a little more important than we 
expect, as the center of the cornea does not move downward along 
a large circle. 
If we know the excursion and the location of the axis, we can 
calculate from these, according to the above-mentioned formulae, the 
rotation, the deorsumduction and the abduction. 
On the other hand, if we have determined by investigation the 
rotation, the deorsumduction and the abduction, we can calculate 
from these the location of the axis in the following way. 
sin H =Vsin®A = sin? D(H = angle between line of vision and y-axis) 
tgu = 9 h Alig i, R 
cos 2 = sine). 77 (sin '/, R sin A + cos'', R sin D) 
sin yp = Ml; (cos? , Resin A — sin '/, R sin DN. 
if the m. obliq. sup. cooperates with one of the other muscles of 
the eye then the rotating-moments of the different axes (w, y and 2- 
axis) can either strengthen or neutralise each other. If the m. obliq. 
sup. cooperates with the m. rectus inf. then the rotating moments 
(for y-axis) can neutralise each other; the rotation downward, the 
deorsumduction, is strengthened. If the m. obliquus sup. cooperates 
with the m. rectus sup., then the moments for rotation round the 
w-axis will be able to neutralise each other, so that the result is an 
almost accurate rotation round the y-axis (reflectory counter-rotation 
when the head is moved round a sagittal axis). A cooperation with 
the m. oblig. inf. will not easily occur, except for fixation of the eye, 
as the planes of motion of these muscles almost coincide. Only with 
abduction a not important cooperation may be expected. 
I wish to discuss a little more elaborately the cooperation of 
the m. obliq. sup. with the m. rectus ext. or with the m. rectus int. 
The view is often expressed that with an abduction of such a nature, 
that the line of vision coincides nearly with the axis of motion of 
the m. obliq. sup. a contraction of this muscle would merely rotate 
the eye inwardly round a sagittal axis, with an adduction on the 
