556 MANUAL OF PHYSIOLOGY. 



ciliary muscle), and also by bands of tissue from the posterior sur- 

 face of the cornea which hold it in position ; the fibres of the cil- 

 iary muscle, running under the ciliary processes, radiate from the 

 margin of the cornea towards the choroid, to which they are at- 

 tached. In a modified form, known as the iris, this vascular and 



Diagram of a horizontal section through the human eye. 1. Cornea; 2. 

 Sclerotic ; 3. Choroid ; 4. Ciliary processes ; 5. Suspensory ligament of 

 lens ; 6. So-called posterior chamber, between the iris and the lens : 7. Iris ; 

 8. Optic nerve ; 8 X . Entrance of central artery of the retina ; 8 /x . Central 

 depression of retina or yellow spot; 9. Anterior limit of the retina; 10. 

 Hyaloid membrane ; 11. Aqueous chamber ; 12. Crystalline lens ; 13. Vit- 

 reous humour ; 14. Circular venous sinus which lies around the cornea ; 

 a a, antero-posterior, and, b 6, transverse axis of bulb. 



pigmented coat of the eye leaves the sclerotic, and hangs freely 

 in a fluid so as to be recognized through the clear cornea as a 

 colored circular curtain, attached to the inside of the periphery 

 of the cornea, and having a central deficiency, which looks black, 



