In hypermetropia, if one causes fixation at about 30 cm. and then covers the eye with the hand, it frequently deviates inwards. Donders infers from this, that most hypermetropes prefer to sacrifice comfortable and clear vision in order to retain binocular vision. Now, it is easy to convince oneself that youthful hypermetropes see distinctly even without correction of their hypermetropia, and we may assume that they see comfortably if they do not complain of asthenopia; but that is by no means always the case, for the appearance of asthenopia is conditional on the relation of the degree of the hypermetropia to the amount of the accommodation, which, apart from a few other causes, depends chiefly on the age of the patient. Just as we refer the deviation outwards of the covered eye to insufficiency of the interni or preponderance of the externi, we may conclude an inward deviation of the covered eye to be due to insufficiency of the externi or preponderance of the interni, and this all the more, as in hypermetropia the covered eye very frequently remains in fixation, and falls away exceptionally into relative divergence. Just as in myopia even in the lesser degrees, insufficiency of the interni or preponderance of the externi is not rare, so in hypermetropia insufficiency of the externi or preponderance of the interni appears to be frequent; and if this disturbance of the muscular balance be followed even in myopia or emmetropia by convergent strabismus, this will of course happen still more easily if at the same time hypermetropia, or even without hypermetropia, the remaining favouring conditions mentioned by Donders are present. Of course I do not deny the effect of the hypermetropia and of those other favouring conditions, but only wish to draw attention to the fact with reference to them, that as a rule they do not of themselves suffice to produce convergent strabismus. Nebulæ have always been regarded as one of the causes of squint; here I quite agree with Donders that they may operate, firstly, as general causes of weak sight; secondly, through this, that the irritated condition, combined with the keratitis, may produce a spasmodic, afterwards a trophic shortening of the muscles; but this seldom happens. Whether nebulæ are found rarely or often in squint, depends in great measure on the statistic materials which are worked out. In my statistics they do not occur in any quantity worth mentioning, because in private practice purulent ophthalmia keratitis, and in short, the whole army of external inflammations of the eye is much rarer, than in that portion of the populace which fills public clinics. Further, it is to be observed that the mere occurrence of nebulæ in squint proves nothing--even squinting eyes may develop keratitis. We must at least require to be assured that the squint began after the keratitis.