178 OKGAtfS OF SENSE. 



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a series of distinct strata, which, proceeding from 

 without inwards, are as follows : 1st, the membrana 

 Jacobi, composed of club-shaped bodies; 2d, the 

 external granular layer, corresponding with the exter- 

 nal enlargements upon the fibres of Muller ; 3d, the 

 internal granular layer, corresponding to the middle 

 enlargements of the same fibres ; 4th, the nervous 

 layer, consisting of nerve cells; 5th, the fibrous 

 layer formed by the fibres of the optic nerve ; 6th, 

 and last, the limitary membrane.* 

 Arteria centraiis The central artery of the retina traverses the 



retinae. * 



papilla of the optic nerve, and is distributed in the 

 more internal layers of the retina. It forms a vas- 

 cular circle around the " yellow spot," and terminates, 

 by a second circular plexus, at the ora serrata. The 

 vein has the same distribution as the artery. 

 vitreous ha- Interior of the eye. Vitreous humor. The vitre- 

 ous humor of the eye occupies the cavity of the 

 retina, and is adherent to that membrane only in 

 the interval between the ora serrata and its anterior 

 margin ; in front it presents a cup-shaped depression 

 which receives the crystalline lens. Its envelope, the 

 hyaloid membrane, is very delicate, structureless, and 

 transparent; interiorly it is somewhat thicker than 

 elsewhere, and gives off two laminae, which invest, 

 respectively, the anterior and posterior surfaces of 



* To obviate any obscurity in the text, arising from the very compen- 

 dious and precise style of the author, who always assumes that his reader 

 is a good descriptive anatomist and possesses alfair knowledge of general 

 structure, it would be well for the student to refer to the admirable work 

 of TODD and BOWMAN, " The Physiological Anatomy and Physiology of 

 Man,'" 1 where fuller details, up to the period of its publication, will be 

 found. Vide Vol. IT., p. 27. London, 1856. 



mor. 



