PRACTICAL NOTES ON HISTOLOGY. 219 



The Choroid is best prepared from an eye hardened in 

 Miiller's fluid. Besides the main substance of the coat contain- 

 ing the larger blood-vessels, the lamina supra-choroidea, the chorio- 

 capillaries, and the membrane of Bruch, should be separately 

 displayed. The posterior attachment of the fibres of the ciliary 

 muscle, and the gangliated plexus of nerves which is found in the 

 neighbourhood of its posterior attachment, will be exhibited with 

 the lamina supra-choroidea. 



Ciliary Muscle and Lamina supra-choroidea.— Divide the 



eye-ball of an ox, sheep, or pig, with a sharp razor, transversely, 

 half inch behind the circumference of the cornea, and remove 

 the lens, but be careful to retain the choroid and iris. Harden 

 the anterior half in chromic acid and spirit. Make horizontal 

 sections to include the sclerotic, cornea, and the iris. Stain with 

 logwood and picro-carmine ; or the anterior part of the eye may be 

 pinned under spirit, and the sclerotic and cornea cut away at one 

 part, when the radiating fibres of the ciliary muscle will be seen 

 passing meridionally from their origin opposite the attachment of 

 the iris, and forming a layer which becomes gradually thinner as 

 it extends backwards, and finally ceases in the superficial part of the 

 choroid. Seize with fine forceps a small piece of the muscle near 

 its origin, and carrying the instrument slowly backwards, it is gradu- 

 ally torn away from the rest. It will be found that the shred 

 which comes away generally spreads out posteriorly into a very 

 thin membranous lamina, which is, in fact, a piece of the lamina 

 supra-choroidea, into which the superficial fibres of the ciliary 

 muscle are inserted. This may be floated directly on to a slide, 

 which is dipped for the purpose into the spirit, wipe off quickly the 

 surplus, and drop some freshly filtered logwood upon the tissue, 

 and allow to remain on it for ten minutes ; pour off the stain 

 and run off the remains by allowing a drop or two of water to 

 flow gently over, without disturbing the position of the membrane. 

 Finally, the cover-glass is to be laid on, and a drop of glycerine 

 allowed to run at its edge. 



Vascular Layers of Choroid and Membrane of Bruch.— These 



are more difficult to separate than the Lamina supra-choroidea, 

 though it is not absolutely necessary to completely separate them 



