US- 



LESSON XXV. 



EYE, EAR, AND OLFACTORY MUCOUS 

 MEMBRANE. 



(a) Section of the Anterior Quadrant of the Eye- 

 ball. 



The anterior half of a human eye was hardened in Miiller's 

 fluid. After hardening, the lens was removed, and a quadrant 

 including a portion of the cornea and sclerotic and ciliary region cut 

 out, stained in Dplafield's hsematoxylin, embedded in paraffin, 

 and sectioned. Fix and mount in balsam. 



Study first under low power. The cornea is composed 

 of 5 layers, named in order from before backward, as 

 follows: 



(1) Stratified pavement epithelium. 



(2) Bowman's layer, or the anterior homogeneous 

 lamella. 



(3) Substantia propria, the thickest of the several 

 coats, composed of bundles of white fibrous tissue arranged 

 in layers, between which the corneal corpuscles are found. 



(4) The posterior elastic or Descemet's membrane. 



(5) The endothelium of the anterior chamber. 



In the sclera the bundles of white fibrous tissue are 

 densely woven, and are continuous with the fibrous tissue 

 bundles of the substantia propria of the cornea, but are not 

 so regularly arranged. Observe the canal of Schlemm as 

 seen in cross-section in the sclero-corneal junction. Of the 

 middle layer, the iris, ciliary body, and anterior portion of 

 the choroid are included in this section. The iris is 

 covered anteriorly by a layer of cells continuous with the 

 ones found on the posterior surface of the cornea. The 

 stroma is a loose fibrous tissue in which pigmented and un- 

 pigmented branched cells and many vessels are found. The 

 iris is covered posteriorly by a double layer of deeply pig- 



