406 



THE EYE IN EVOLUTION 



Fig. 499. — The Ciliary Kegion of the Goshawk, Astur palvmbariur. 



B, Bi'ucke's muscle ; C, cornea ; CM, Ci'ampton's muscle ; CP, ciliary 

 processes; M, MuUer's muscle ; O — O, ring of ossicles ; P, ciliary process abut- 

 ting the lens capsule ; S, fibrous sclera ; ST, subconjunctival tissue ; T, 

 tenacular ligament ; V, ciliary venous sinus (after H. Miiller, 1857). 



The cassowur;; 

 Casuarius 



Fig. 500. — The Striated Fibres of Crampton's Muscle in the Chicken 

 ( X 240) (Norman Ashton). 



/ 



These muscles are of considerable interest and have received much study. 



Crampton (1813) first described a muscle in this region in the ostrich, Struthio, 



and the anterior segment of the ciliary musculature has been called eponymously 



after him ; he termed it the depressor cornece. Thirty-three years later, Briicke 



(1846) described a more posteriorly situated muscular zone in the eagle-owl. 



Bubo orientalis, and the cassowary, Casuarms, calling it the tensor choroidece. 



Sometimes this latter muscle is divided into two — an anterior portion {Muller''s 



uiuscle) which was first described by this author (1856) in the hawk, Accipiter, 



and a posterior, Brikke^s muscle. There is probably little functional difference 



between these slips of muscles thus separated anatomically, nor is it easy to 



'■'cide which is their fixed and which their mobile attachment ; connected as 



y are by aponeurotic membranes, they probably form a single functional 



-'em. 



