—117— 



(c) Retina. 



Tlie postprior half of a limiian eye was lianlened in mercuric 

 cliloride. Small i)iecesof the retina were removed, stained in Dela- 

 field's hioinatoxylin, embedded in i):iraffin. and sectioned. Fix to 

 tlie slide, and mount in balsam. 



T^se lii.uh power. The following layers are made out, 

 n:ini'(l in order from before baekward : — 



( 1 ) Internal limiting membrane. 



(2) La^^er of nerve fibres. 



(3) Lnyer of ganglion cells. 



(4) Innei- granular or molecular layer. 



(5) Inner nuclear layer. 



(6) Outer granular or molecular layer. 



(7) Outer nuclear layer. 



(8) Outer limiting membrane. 



(9) Layer of rods and cones. 



(10) Liiyer of pigment cells; this layer often remains 

 attached to the choroid, and may therefore not be seen in 

 your section. 



Sketch under high power. 



(d) Optic Papilla. 



The posterior [lart of a human eye was hardened in 3Iuller's 

 tluid. The optic papilla with a small portion of tlie posterior wall and 

 entering optic nerve was I'emoved, stained in Delafielil's luematoxy- 

 lin, embeilded in paraffin, and sectioned. Fix and mount in balsam. 



Study first under low power. Note the dural and arach- 

 noidal sheaths of the oi)tic nerve. They are continuous 

 with the sclerotic. The optic nerv^e fibres passing through 

 the lamina cribrosa and bending over and spreading out to 

 form the layer of nerve fibres of the retina, are to be observed. 

 Notice the excavation in the optic papilla. The nerve 

 fibres of the retina are on the anterior surface; the rods 

 and cones point toward the sclerotic. The section may 

 show the artery centralis retina in longitudinal, and some 

 of its l)ranches in cross or obliqvH), section. Sketch under 

 low power. 



(e) Cochlea of a Guinea Pig. 



The cochlea of a cuinea pig was hardened in Flemming's solu- 

 tion, decalcified in 1 % chromic acid, and embedded in celioidin. 



