THE IRIS. 



313 



had been seen in animals by the greater number of authors is indis- 

 putable, and it is equally probable that they then transferred the results 

 of their observations directly to Man, yet this is certainly not feasible 

 on the ground of the peculiarities which the whole arrangement of the 

 accommodation and the muscular mechanism exhibit in Man. The 

 peculiarities in the structure of the dilatator in Man compel Henle 

 himself to make the correct statement that no agreement exists between 

 the object of his description, and that which has been described as the 

 dilatator by Briicke and Henle. 



Kolliker* does not attempt to conceal the fact that his account is taken 

 from that of the dilatator of the Rabbit. According to him, the dila- 

 tator consists of several thin fasciculi which lie between the vessels, and 



Fig. 366. Disposition of the muscular fasciculi of the iris. The 

 lettering explained in the text. 



consequently in the substance of the iris. Henlef refers to a special 

 layer of fibres which he finds on the internal surface of the iris, and 

 is of opinion that in this homogeneous and continuous, though very 

 thin, layer of radial fibres extending from the pupillary to the ciliary 

 border he has discovered the muscle, the contraction of which effects 

 the dilatation of the pupil. 



This statement led to further researches upon the dilatator. Ac- 

 cording to Hiittenbrenner,J the dilatator in Rabbits is formed by the 

 continuous layer of muscular fibres described by Henle, lying imme- 

 diately behind the epithelium, which in that animal represents the 



* Handbuch der Gewebelehre des Menschen, 1867, 667. 

 t Handbiich der systematischen Anatomie des Menschen, Bandii., p. 635. 

 Sitzungsberichte d. K.-Akademie der Wissenschaften zu Wien, Ab- 

 theilungi., 1868. 



