ENERGY AND RAPIDITY OF MUSCULAR CONTRACTION. 917 



adverted to in reference to this subject : Strabismus not unfrequently arises 

 from the presence of an opaque spot on the centre of the cornea, which prevents 

 the formation of any images on the retina, except by the oblique rays; and 

 nature seems to endeavor (so to speak) to repair the mischief, by causing the 

 eye to assume the position most favorable for the reception of these. 1 



3. Energy and Rapidity of Muscular Contraction. 



921. The energy of Muscular contraction is, of course, to be most remarka- 

 bly observed in those instances in which the continual exercise of particular 



1 In reference to this subject, the Author would add that he is well convinced, from 

 repeated observation, that those Surgeons are in the right who have maintained that, in a 

 large proportion of cases, strabismus is caused by an affection of both sets of muscles or 

 nerves, and not of one only ; and that it then requires, for its perfect cure, the division of 

 the corresponding muscle on both sides. Cases will be frequently met with, in which this 

 is evident ; the two eyes being employed to nearly the same extent, and the patient giving 

 to both a slight inward direction, when desired to look straight forwards. In general, 

 however, one eye usually looks straight forwards, whilst the other is greatly inverted ; 

 and the sight of the inverted eye is frequently affected to a considerable degree by disuse ; 

 so that, when the patient voluntarily rotates it into its proper axis, his vision with it is far 

 from being distinct. Some Surgeons have maintained that the inverted eye is usually the only 

 one in fault, and consider that the division of the tendon of its Internal Rectus is sufficient 

 for the cure. They would even divide its other tendons, if the parallelism be not restored, 

 rather than touch the other eye. The Author is himself satisfied, however, that the restric- 

 tion of the abnormal state to a single eye is the exception, and not the rule, in all but 

 very slight cases of strabismus ; and to this opinion he is led both by the consideration of 

 the mode in which strabismus first takes place, and by the results of the operations which 

 have come under his notice. If the eyes of an infant affected with cerebral disease be 

 watched, there will frequently be observed in them very irregular movements ; the axes 

 of the two being sometimes extremely convergent, and then very divergent. This irregu- 

 larity is rarely or never seen to be confined to one eye. Now, in a large proportion of 

 cases of Strabismus, the malady is a consequence of some cerebral affection during infancy 

 or childhood, which we can scarcely suppose to have affected one eye only. Again, in other 

 instances we find the Strabismus to have resulted from the constant direction of the eyes 

 to very near objects, as in short-sighted persons ; and here, too, the cause manifestly affects 

 both. Now it is easy to understand, why one eye of the patient should appear to be in its 

 natural position, whilst the other is greatly inverted. The cause of strabismus usually 

 affects the two eyes somewhat unequally, so that one is much more inverted than the 

 other. We will call the least inverted eye A, and the other B. In the ordinary acts of 

 vision, the patient will make most use of the least inverted eye, A, because he can most 

 readily look straight forwards or outwards with it ; but to bring it into the axis, or to 

 rotate it outwards, necessitates a still more decided inversion of B. This remains the posi- 

 tion of things the patient usually looking straight forwards with A, which is the eye con- 

 stantly employed for the purposes of vision and frequently almost burying under the 

 inner canthus the other eye. B, the vision in which is of very little use to him. When, 

 therefore, the tendon of the internal rectus of B is divided, the relative position of the two 

 is not entirely rectified. Sometimes it appears to be so for a time ; but the strabismus 

 then begins to return, and it can only be checked by division of the tendon of the other 

 eye, A ; after which, the cure is generally complete and permanent. That it has not been 

 so, in many of the patients on whom operations have been performed, the Author attributes, 

 without the slightest doubt in his own mind, to the neglect of the second operation. As 

 just now stated, the sight of the most inverted eye is frequently very imperfect ; indeed 

 it is sometimes impaired to such an extent, that the patients speak of it as entirely use- 

 less. That this impairment results in part from disuse merely, seems very evident from 

 the great improvement which often succeeds the rectification of the axes. The Author 

 cannot help thinking it probable, however, that the same cause which produced the dis- 

 tortion of the eye may, in some instances at least, have affected the Optic nerve, as well 

 as the motor nerves of the orbit ; and this idea seems borne out by the asserted restora- 

 tion of sight, in certain cases of Amaurosis, by division of one or more tendons, where no 

 Strabismus previously existed (See Adams " On Muscular Amaurosis"). A valuable me- 

 moir on the operation for Strabismus, founded on the results of about 1000 cases, will be 

 found in the " Philadelphia Medical Examiner," vol. vii., and an abstract of it in the 

 "Brit, and For. Med.-Chir. Review," July, 1852, p. 262. 



