Scientific Credulity 29
"The greatest thinkers," says Cohn, "have mastered a host of difficulties in discovering this arrangement, and it is only in very recent times that its processes have been clearly and perfectly set forth in the works of Sanson, Helmholtz, Brticke, Hensen and Volckers."1
Huxley refers to the observations of Helmholtz as the "facts of adjustment with which all explanations of that process must accord,"2 and Donders calls his theory the "true principle of accommodation."3
Arlt, who had advanced the elongation theory and be lieved that no other was possible, at first opposed the conclusions of Cramer and Helmholtz,4 but later accepted them.5
Yet in examining the evidence for the theory we can only wonder at the scientific credulity which could base such an important department of medical practice as the treatment of the eye upon such a mass of contradictions. Helmholtz, while apparently convinced of the correct ness of his observations indicating a change of form in the lens during accommodation, felt himself unable to speak with certainty of the means by which the sup posed change was effected,6 and strangely enough the question is still being debated. Finding, as he states, "absolutely nothing but the ciliary muscle to which ac commodation could be attributed,"7 Helmholtz concluded that the changes which he thought he had observed in the curvature of the lens must be effected by the action of this muscle; but he was unable to offer any satisfac-
1 The Hygiene of the Eye in Schools, English translation edited by Turnbull, 1886, p. 23. Hermann Cohn (1838-1906) was professor of ophthal mology in the University of Breslau, and is known chiefly for his con tributions to ocular hygiene.
2 Lessons in Elementary Physiology, sixth edition, 1872, p. 231.
8 On the Anomalies of Accommodation and Refraction of the Eye, p. 13. 4 Krankheiten des Auges, 1853-56, vol. iii, p. 219, et seq. 8 Ueber die Ursachen und die Entstehung der Kurzsichtigkeit, 1876. Vor-wort.
8 Handbuch der physiologischen Optik, vol. i, pp. 124 and 145. 'Ibid, vol. i, p. 144.