784 
PT and PT positive, when 7’ lies temporalward from 7; conse- 
quently 47 OPT will be positive, when © lies under PT and 
temporalward from P or over PT’ and noseward from P. 
If now we apply this rule, we shall find a positive value for the 
rotation, when the upper part of the vertical meridian of the retina 
inclines too much temporalward, a negative value when it inclines 
too much noseward. 
For all our calculations we have consequently to measure on 
the wall: OR, PR, OT and PT, whilst the distance from the eye 
to the wall must be known. 
Now we can ask how the axis lies, round which the eye would 
have to come from the primary position into the position we 
have found. 
Some formulas for its calculation have been given in the communi- 
cation mentioned above. I think it a good plan to repeat these 
formulas again, not only because this gives me an opportunity to 
correct a few tronblesome printer’s errors, but likewise because | 
can call attention to the fact, that these formulae do not serve 
exclusively to find the axis of the m. obliquus superior, but that 
they are of a much more general signification. In the former 
communication the rotation was called positive, when the upper part 
of the vertical meridian of the retina inclined nose-wardly ; in con- 
nection with what is generally understood by positive cyclophory, 
I suppose, I have been obliged to rectify this likewise. 
The formulas mentioned run consequently : 
sin H = V sin? A + sin? D 
tq 3 H N ea 
tg 4-=—__._ (u is always less than 905). 
sin |, R : 
; sin “f ; os 
cos 4 = — —— (sin D cos */,R — sin A sin '/, R) 
sin 
Sa ; : 
cos » —= — —— (sin D sn*/, R + sin A cos'/, R) 
sin H A 
in which H = the angle between the line of regard in the position 
we have found and the primary position, A — Abduction, D = 
= Deorsumduction, R= Rotation temporalward. 4= angle of the 
anterior half of the axis of motion with z-as (temporalward). u= 
= angle of the anterior half of the axis of motion with y-axis (for- 
ward. r=z=angle of the anterior half of the axis of motion with 
z-axis (upward). The sign before u indicates the direction in which 
the eye has rotated. 
