314 TUNICA VASCULOSA, BY PROF. A. IWANOFF. 



pigment layer. This muscle extends to the ciliary border, and some of 

 its fibres can easily be followed as far as to the ligamentum pectmatum. 

 It is obvious that this is not the muscle seen in Rabbits by Kolliker. 

 In Hiittenbrenner's opinion, the dilatator in Man is similarly disposed. 

 Thus it appears that this author, with the single exception of the 

 passage of muscular fibres into the ligamentum pectmatum, corrobo- 

 rates the views of Henle, not only in the case of Man, but in that of 

 animals. 



The account of the dilatator given by Merkel,* on the other hand, is 

 more in accordance with Kolliker 's definition ; he does not describe a 

 continuous layer unbroken by perforations, such as Henle saw, but a 

 number of isolated fasciculi, which however, as Henle states, are 

 placed immediately behind the pigment. 



Dogielf described a muscle which answers to the descriptions 

 given by Briicke and Kolliker ; it commences at the sphincter, on the 

 anterior surface of the iris ; then, divided into separate fasciculi, runs 

 outwards between, the vessels, and is attached to the ciliary ring. 



In view of these conflicting statements, I suggested to Herr Jerop- 

 heeff to examine the dilatator in Man. The results of his investigation 

 are given above, and are in complete accordance with Henle' s de- 

 scription. Herr Jeropheef has also been successful in discovering 

 circular fasciculi at the ciliary border. 



The nerves of the human iris, in consequence of the great 

 difficulties that oppose themselves to their investigation, have 

 as yet been very unsatisfactorily examined. The best account 

 is that given by Arnold,;}: which, however, treats only of the 

 nerves of the Rabbit. 



The nerves of the iris are branches of the ciliary nerves of 

 the choroid. On reaching the iris, they divide dichotomously 

 in its external parts ; form arches, and then break up into a 

 plexus consisting of medium-sized branches of nerves. In this 

 plexus an interchange of fibres takes place between the nerve- 

 trunks, which strongly resembles the grouping of the fibres in 

 the chiasma nervorum opticorum. 



Three kinds of nerve fibrils proceed from these points of 



* Zeitschrift fur rat. Medicin, Bande xxxi. and xxxiv. 

 t Archiv fur Mikroskopische Anatomie, Band vi., p. 95. 

 | Archiv fur pathol. Anatomie und Physiologie, Band xxvii, Ueber die 

 Nerven und das Epitlid der Iris. 



