s. HOLTH AND O. BERNER. M.-N. KL 



I have also depigmented a part of my control material with hydrogen 

 peroxide with particularly good results. For this purpose I have used con- 

 centrated hydrogen peroxide from E. Merck, Darmstadt. In order to start the 

 development of gas in the fixed material, I have added, b}' the advice of 

 Professor Torup, a very few drops of a weak solution of ammonia. This 

 makes good the loss of the enzymes that may have been destroyed in the 

 tissue during the process of fixing. I can thoroughly recommend this man- 

 ner of depigmentation for ordinary material, but would not advise its employ- 

 ment on valuable material, such as irides from miotic eyes; for gas-bubbles- 

 may sometimes develop in the substance of the iris, and thus cause its 

 deformation. 



With regard to the direction of sections and staining I refer the reader 

 to my previous paper (Bibl. 6). The study of this new case is based exclusively 

 upon serial sections, and they have been an inestimable advantage to me. 



As the two sets of material that I have had for examination came 

 from a twin brother and sister, it might have been reasonable to expect 

 that the microscopical representation of the eye would be the same in both, 

 more especially as the clinical phenomena were so similar. Anatomicall}', 

 however, they vary considerably, although there are also great similarities; 

 and it must be remembered that whenever twins are of two sexes, they 

 have come from two different ova. Had these twins been of the same sex^ 

 they might possibly have come from one ovum, and in that case it would 

 have been reasonable to expect that the anatomical features would have 

 been the same in both. As they were of different sexes, however, it is not 

 to be wondered at that there is a considerable difference between their eyes. 



The great difference between these two cases of congenital miosis is 

 that in the man's ej'es there is a well-developed dilatator muscle, not only 

 behind the sphincter, as was the case with his sister, but also in the inter- 

 mediate part towards the ciliar}^ processes. But before the ciliary processes 

 are reached, the dilatator always ceases in the man's eye, so that with him 

 too, there is no dilatator in the periphery of the iris. I have calculated the 

 part of his irides that is without dilatator to be from about ^ 8 to ^' lO. ' 

 Fig. 3 gives a diagrammatic general view of his iris, and the difference 

 between the eyes of the twins is immediately apparent on comparing this 

 figure with fig. 6 on PI. II of my previous paper. One peculiarity in the 

 brother's irides is that the boundary between the parts of the iris that are 

 respectively with and without dilatator, is formed by a curious "projection^', 

 which I have shown in the detail-figure, fig. 4. From the photograph repro- 

 duced in fig. 5 it is further seen that the outermost part of the iris is much 

 thinner than the part with dilatator, and that the boundary between these 

 zones is distinct, and also that the outermost part (without dilatator) gives 



' See Plate I, Fig. 3; elsewhere it is '/s (fig. 5) or even more where there is no 'pro- 

 jection". 



