Transactions . part of the same globe, showing the cyst andfibroiTS vitreons. in contact with its outer pigment cell layer in the posteriorpart of the globe. The mesoblastic tissue which wouldform the vitreous is developed as fibrous bands which,unless the condition is considered as a whole, might bethought to cause the retinal sepaiation due to its beingheld out of place by the bands of Tnesoblastic tissue, but,as has already been shown, in the case where there is noglobe similar fibrous tissues occur. These latter are reallydeveloped secondarily as the result of the inner layersof the optic
Transactions . part of the same globe, showing the cyst andfibroiTS vitreons. in contact with its outer pigment cell layer in the posteriorpart of the globe. The mesoblastic tissue which wouldform the vitreous is developed as fibrous bands which,unless the condition is considered as a whole, might bethought to cause the retinal sepaiation due to its beingheld out of place by the bands of Tnesoblastic tissue, but,as has already been shown, in the case where there is noglobe similar fibrous tissues occur. These latter are reallydeveloped secondarily as the result of the inner layersof the optic cup being pushed inwards by its distensionof fluid, no proper space being allowed for the develop- Detachment of the retina. 123 ment of the mesoblast into tlie vitreous. For if thedetachment were due to the pull of these bands a negativepressure Avould be present in the inter-retinal space, andthere would be no reason for the formation of cysticprotrusion in the posterior part of the globe (Fig. 13). Fig. Microphthalmos in a fully formed globe, showing a congenitaldetachment of the retina. The darkly-stained material in theinter-retinal space is blood-clot formed at the time of enuclea-tion. Where the globe is still better formed the eye, althoughslightly microphthalmic, may be a completely enclosedcavity showing no external cysts; but still the inner layerof the optic vesicle is not in contact with the outer. Sucha case has been shown before this Society by the authorin April, 1914 (Fig. 14). In this instance there was comparatively little fibrousvitreous, and the anterior portion of the primary optic 124 DETACHMENT OF THE REtINA. vesicle had united together, forming-the iris and ciliarybody, whilst the posterior part of the retina was separatedfrom its pigment cell layer by flnid. At the line of theunion anteriorly there was an overgrowth of the outerpigmented layer to form a congenital pigmented tumourof the ciliary body. No ora serrata was present, thecondition being
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