22 S. IIOLTII AS!) O. l'.KRNEK. M.-N. Kl. 



explain ihc origin of the broad strengthening bands that I have found in 

 any other way than by proliferation. Fig. 13 shows no bending of the 

 e[)itheliLim, and thus (old-f(jnnation can scarcely be connected in any way 

 with its origin. Moreover, as already mentioned, my fig. 11 shows that 

 in front of the double-layered epithelium there is a single long, thin cell, 

 that may possibly be a not yet fully developed muscle cell; and according 

 to this, Foksmark's theory of proliferation and displacement with change 

 of th': cell's form, may very well be correct. The only figures wanting 

 are of cell-division, but they will perhaps be obtained from future cases. 

 I have seen no sign of cell-division in my slides. 



With regard to the aplasia that appears in my material, and which 

 according to Forsmark, is not infrequently to be found in the peripheral 

 part of the iris, it must be remembered that previously Szily had also 

 described such an aplasia, which he also found affected the dilatator rudi- 

 ment. According to Szily, "in a few places" small groups of cells escape 

 the transformation into dilatator elements, so that islands of large, proto- 

 plasmic epithelium cells are found lying between the posterior layer of the 

 iris epithelium and the dilatator muscle. Concerning the frequency of these 

 occurrences, all that Szily appears to say is found in his resumé, where he 

 mentions that they are found 'an sehr vereinzelten Stellen"; but in his dia- 

 grammatic drawing of the iris, two places where aplasia appears are marked, 

 so it would not seem to be so rare. 'As Kopsch also employs Szily's 

 figure without any alteration in his edition of Rauber's anatomy, one would 

 imagine that aplasia of the dilatator pupillae is not uncommon. Personally 

 I have no experience of this. Heerfordt has also found signs of aplasia. 

 On p. 533 of his work, where he describes the large folds which in the 

 rabbit extend right up to the ciliary processes, he says that the two layers 

 of epithelium cells cannot be clearly distinguished from one another, and 

 that the cells of the front layer seem to be "only imperfectly" transformed 

 into muscle cells. 



As our knowledge of the details of the structure of the dilatator is 

 still incomplete, and as pathological anatomy has so often thrown light 

 upon obscure points in normal anatomy, it might be expected that this 

 work would perhaps contribute to our knowledge of the still doubtful points 

 concerning the muscle that has perhaps been more discussed than an}' other. 



Although I have little worth mentioning to contribute, 1 feel it to be 

 my duty to submit my material in its relation to these obscure points in 

 our knowledge of the more delicate structure of the dilatator pupillae. 



