The delicate mechanism of the eye is one of the first portions of the nervous apparatus to be disturbed by any undue strain on the system; it is not surprising that masturbation should be widely incriminated as a cause of eye troubles.  If, however, we inquire into the results obtained by the most cautious and experienced ophthalmological observers, it grows evident that masturbation, as a cause of disease of the eye, becomes merged into wider causes.  In Germany, Hermann Cohn, the distinguished ophthalmic surgeon of Breslau, has dealt fully with the question.[318] Cohn, who believes that all young men and women masturbate to some extent, finds that masturbation must be excessive for eye trouble to become apparent.  In most of his cases there was masturbation several times daily during from five to seven years, in many during ten years, and in one during twenty-three years.  In such cases we are obviously dealing with abnormal persons, and no one will dispute the possibility of harmful results; in some of the cases, when masturbation was stopped, the eye trouble improved.  Even in these cases, however, the troubles were but slight, the chief being, apparently, photopsia (a subjective sensation of light) with otherwise normal conditions of pupil, vision, color-sense, and retina.  In some cases there was photophobia, and he has also found paralysis of accommodation and conjunctivitis.  At a later date Salmo Cohn, in his comprehensive monograph on the relationship between the eye and the sexual organs in women, brought together numerous cases of eye troubles in young women associated with masturbation, but in most of these cases masturbation had been practiced with great frequency for a long period and the ocular affections were usually not serious.[319] In England, Power has investigated the relations of the sexual system to eye disease.  He is inclined to think that the effects of masturbation have been exaggerated, but he believes that it may produce such for the most part trivial complaints as photopsisae, muscsae, muscular asthenopia, possibly blepharospasm, and perhaps conjunctivitis.  He goes on, however, to point out that more serious complaints of the eye are caused by excess in normal coitus, by sexual abstinence, and especially by disordered menstruation.  Thus we see that even when we are considering a mechanism so delicately poised and one so easily disturbed by any jar of the system as vision, masturbation produces no effect except when carried to an extent which argues a hereditarily imperfect organism, while even in these cases the effects are usually but slight, moreover, in no respect specific, but are paralleled and even exceeded by the results of other disturbances of the sexual system.