PROFESSOR AT KONIGSBERG 107 



the contrivance of a special instrument for measuring the very 

 small electrical currents which du Bois had observed in muscles. 

 In addition to this he embarked on a protracted study of the 

 adaptation of the eye for different distances, which was, however, 

 interrupted by the discoveries of a young Dutch physiologist, 

 Cramer. As early as January 23, Helmholtz sent du Bois 

 a short preliminary notice for the Academy 'On a hitherto 

 unknown Alteration in the Human Eye, during Altered Accom- 

 modation '. In this he describes an observation made as early 

 as the winter of 1852, that in accommodation for near objects, the 

 image reflected from the front surface of the lens is diminished 

 to nearly half its size, a considerable alteration which cannot 

 be explained by a change of position of the lens, but only on 

 the supposition that there is an alteration of its form by the 

 increased curvature of the anterior surface. He had previously 

 determined by many exact observations that the edge of the 

 pupil bulges outwards in near vision. 



In March he joyfully communicates his ' little discovery in 

 regard to the accommodation of the eye ' to Ludwig, as pub- 

 lished in the monthly reports. But on July 3 he informs him : 

 ' Bonders has written to tell me that a Dr. Cramer has been 

 before me, his paper having been "crowned" in 1851 by the 

 Haarlem Society, though it is only now being published : I 

 shall receive a copy of it shortly. Lately there have been 

 a good many coincidences between my work and that of others : 

 (i) on Brewster's Theory ; a portion of my results were also 

 discovered by a young physicist, Felix Bernard, and published 

 in the Annales de Phys. et Chim. in the same month in which 

 mine appeared in Poggendorff, but he had communicated the 

 work some time before to the French Faculty : (2) in January 

 Gaugain brought out a tangent galvanometer, .on the principle 

 of the one I had made in 1849 for du Bois-Reymond's ex- 

 periments ; mine, however, is more convenient and better : 

 (3) Foucault describes a method for the uniform lighting of 

 large surfaces with homogeneous or mixed light; I received 

 his paper after myself inventing and constructing the ap- 

 paratus: (4) Cramer on Accommodation; I am most curious 

 to see this paper. Your textbook, so far as it goes at present, 

 is my faithful friend when I am preparing my lectures.' 



The promised copy of Cramer's paper was so long delayed 



