500 



ZONULA C1LIARIS. 



it is surrounded by a yellow halo, the limlus luteus, and is frequently 

 obscured by an elliptical fold of the retina, which, from its constancy 

 of appearance, has been regarded as a normal condition of the mem- 

 brane. The term foramen is misapplied to this spot, for the vascular 

 layer and the membrana Jacobi are continued across it ; the nervous 

 substance alone appearing to be deficient. It exists only_ in animals 

 having the axis of the eyeballs parallel with each other, as man, 

 quadrumana, and some saurian reptiles, and is said to give passage to 

 a small lymphatic vessel. 



Fig. 155.* 



The Zonula ciliaris (zonula of Zinn)f s a thin vascular ayer, 

 which connects the anterior margin of the retina with the anterior 

 surface of the lens near its circumference. It presents upon its sur- 

 face a number of small folds corresponding with the ciliary processes, 

 between which they are received. These processes are arranged in 

 the form of rays around the lens, and the spaces between them are 



plates which accompany his works. The account " De Foramine Centrali Re- 

 tinae Humanae, Limbo Luteo cincto," was published in 1779, in the Com- 

 mentationes Soc. Reg. Scient. Gottingensis. 



* The posterior segment of a transverse section of the globe of the eye, 

 seen from within. 1. The divided edge of the three tunics. The membrane 

 covering the whole internal surface is the retina. 2. The entrance of the optic 

 nerve with the arteria centralis retinae piercing its centre. 3, 3. The ramifica- 

 tions of the arteria centralis. 4. The foramen of Soemmering, in the centre of 

 the axis of the eye ; the shade from the sides of the section obscures the limbus 

 luteus which surrounds it. 5. A fold of the retina, which generally obscures 

 the foramen of Soemmering after the eye has been opened. 



t John Gottfried Zinn, professor of Anatomy in Gottingen ; his " Descriptio 

 Anatomica Oculi JIumani," was published in 1755; with excellent plates. It 

 was republished by Wrisberg in 1780. 



