SYSTEMATIC SYNTHESIS OF TISSUES INTO ORGANS. 297 



'774. THE USE OF THE IKIS is to admit more or less 

 light ; hence it will be large in a feeble and small in a 

 bright light. 



775. THE CRYSTALLINE LENS, 11, is the third medium 

 of the eye, shaped as shown, and enclosed in its capsule. 



776. THE CRYSTALLINE LENS is CONSTRUCTED of sin- 

 ewy fibres arranged in layers like coats of an onion, and 

 also in several sections. It is very beautiful ; no diamond 

 of the choicest water equals its transparency ; and could 

 it be taken from the eye and consolidated with all its 

 primitive beauty, no gem from Golconda's mines would 

 equal its price. 



777. THE FOURTH MEDIUM OF THE EYE, 13, the vit- 

 reous (glassy) humor, fills all the back part of the eye 

 between the lens and the retina. 



778. THE VITREOUS HUMOK is CONSTRUCTED of the 

 hyaloid (glass-like, from its transparency,) membrane, 

 that entirely encloses the vitreous, lying against the re- 

 tina; it intersects the vitreous, dividing it into small 

 spaces filled with a watery fluid. Through the centre 

 the central artery, 1 7, extends to the capsule of the lens. 

 The artery, as shown, is enclosed by the hyaloid. 



779. THE FRONT SURFACE OF THE VITREOUS sur- 

 rounding the crystalline is indented; the indentations, 60 

 or 70 in number, receiving folds of a membrane, called 

 the ciliary processes, triangular in form, that with the 

 spaces between them occupy the side, 5, of the posterior 

 chamber of the eye. They are also attached to the front 

 part of the choroid, and to the iris near its attachment. 

 Their surfaces and the intervening surface of the hyaloid 

 are pervaded by black pigment-cells. 



780. IN THE FOLDS OF THE CILIARY PROCESSES mUS- 



cular fibres are found, extending backward and forward, 

 which, by their contraction, will draw forward the lens, 

 and also affect the densities of both humors of the eye. 



774. What is ? 775. What is ? 776. How is ? 777. What is - ? 778. How 

 is ? 779. What said of ? 780. What found ? 



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