August 1, 1902.] 



SCIENCE. 



189 



One of the fundamental notions in Dr. 

 Savage's book and one that affects the reason- 

 ing all through it is found in the statement 

 on p. 2 : 



"With this axis [the visual axis] the four 

 recti muscles are alone^ concerned as to the 

 final result of their action. The superior and 

 inferior recti of the two eyes are required 

 to keep the visual axes always in the same 

 plane. * * * The oblique muscles are re- 

 quired to so relate the vertical antero-pos- 

 terior planes of the two eyes that the vertical 

 axes which lie in these planes may be parallel 

 with each other, and with the vertical plane of 

 the head." The inference is that the superior 

 and inferior recti are practically the only mus- 

 cles concerned in elevating and depressing the 

 eyes, and the obliques the only ones that ro- 

 tate the vertical meridians or keep these 

 meridians vertical. And that this is his view 

 is shown unmistakably by the further state- 

 ment (p. 4) : "Each of the conjugate innerva- 

 tion centers controls two muscles, one for 

 either eye. The first [serving to elevate both 

 eyes] controls the two superior recti; the 

 second [serving to depress both eyes], the 

 two inferior recti; * * * the sixth [serving 

 to keep the vertical axes from diverging 

 above], the two sujaerior obliques; the seventh 

 [serving to keep the vertical axes from con- 

 verging above], the two inferior obliques." 

 So also his eighth and ninth centers, which 

 are supposed to keep the vertical axes of both 

 eyes parallel with the median plane of the 

 head in the oblique positions of the gaze, 

 control respectively the right superior and left 

 inferior, and the right inferior and left su- 

 perior obliques. 



Now if there is one fact in regard to the 

 eye-muscles that is demonstrated alike by 

 anatomy, by physiology and by clinical inves- 

 tigations, it is that in elevation of the eye 

 both the superior rectus and the inferior 

 oblique take part, and that about equally, al- 

 though in the straightforward direction of 

 the gaze the superior rectus is the more effi- 

 cient of the two. The elevating center, there- 

 fore, controls the two inferior obliques quite 



* Italics mine. 



as much as it does the two superior recti; and 

 the depressing center controls the two superi- 

 or obliques as well as the two inferior recti. 

 So too both physiological investigations and 

 a study of the resvilts of paralysis show that 

 the inferior and superior recti quite as much 

 as the obliques are concerned in producing 

 torsion of the vertical meridians, and Savage's 

 various centers, by which this torsion is regu- 

 lated and the vertical meridians kept vertical 

 and parallel, must govern these recti as well 

 as the obliques. 



It is but just to say that Dr. Savage himself 

 admits this, at least in part, in speaking of 

 the action of the individual muscles (pp. 39 

 et seq.) ; and it seems all the more strange 

 that he should not 'recognize the bearing of 

 this admission upon his theories of the com- 

 bined actions of these same muscles, produced 

 by the coordinating centers. 



The error above noted has an important 

 practical consequence. It leads Dr. Savage 

 to the further erroneous teaching that in the 

 diagnosis of paralysis of the various muscles, 

 it is sufficient to determine the curtailment 

 of rotation or determine the amount of diplo- 

 pia in the four cardinal directions only (up, 

 down, in and out). This would be so if, as 

 he assumes, the four recti alone acted to carry 

 the eyes in these various directions. If, for 

 example, the inferior rectus was the only mus- 

 cle that depressed the eye, measurement of the 

 degree of downward rotation would indicate 

 whether the inferior rectus was weak or not. But 

 since the superior oblique takes a very large 

 part in perforining this downward rotation, 

 we cannot, from the mere fact that this rota- 

 tion is limited, infer that the inferior rectus 

 is weak. We can do so only by demonstrating 

 that the limitation of movement increases 

 markedly in looking downward and outward 

 and diminishes to zero in looking downward 

 and inward. 



In fact for diagnosticating weakness or pa- 

 ralysis of the individual muscles, we must 

 determine the range of excursion of the eyes 

 or the amount of diplopia in six, not in four, 

 cardinal directions, viz., right, left, up and 

 right, up and left, down and right, down and 

 left. Unless this fact is realized, the diagno- 



