AND PHYSIOLOGY. 



the inner side of a hollow sphere, formed by the membranes 

 already mentioned. 



684. Microscopic Structure of these Membranes. — 

 The structure of these membranes, as revealed by the micro- 

 scope, is very complex. The Cornea is made up of four sim- 

 ple membranes, the Choroid of three, and the Retina of four. 



Fig. 344. 



Vertical Section of the Human Retina and Hyaloid Membrane A, Hyaloid Membrane. 

 h f , Nuclei on its inner surface, c, Layer of Transparent Cells, connecting the Hyaloid 

 and Retina, c r , Separate Cell enlarged by imbibition of water, n, Gray Nervous Layer, 

 with its Capillaries. 1, Its Fibrous Lamina. 2, Its Vesicular Lamina. V, Shred ot Fi- 

 brous lamina detached. 2', Vesicle and Nucleus detached, g, Granular Layer. 8, Light 

 Lamina frequently seen, g', Detached Nucleated Particle of the Granular Layer, m, Ja- 

 cob's Membrane. m\ Appearance of its Particles, when detached, m", Its Outer Sur- 

 face. — Magnified 320 diameters. 



The Sclerotic is for the most part made up of white fibrous 

 tissue, and a large portion of the Choroid coat is composed of 

 blood-vessels, although the inner membrane — the Pigmentum 

 Nigrum or black paint — consists of minute six-sided cells re- 

 sembling a tesselated pavement. The Retina is for the most 

 part made up of the different forms of nervous tissue and its 

 membranes. 



634. Give the microscopic structure of the cornea. Of the choroid, the pigment, and 

 the retina. 



