CHOROIDAL AND IRIS ANGIOARCHITECTURE OF THE NEWT - A SCANNING ELECTRON-MICROSCOPIC STUDY OF VASCULAR CORROSION CASTS

The corrosion cast technique provided for the first time an excellent three-dimensional visualization of the vascular pattern of the choroid and iris in the newt eye. The results show the presence of a single a rterial afference to the choroidal and iris capillaries: the ophthalmi c artery is the origin of both ciliary arteries and the long posterior ciliary artery. Slightly behind the equatorial circumference of the e yeball the venous drainage consists of a single vessel on the dorsal s ide and two distinct vessels on the ventral one. It receives blood fro m both iris and choroid. The surface of the plastic endocasts shows so me details of fine luminal structures of the endothelial cells. Shallo w depressions may be regarded as imprints of endothelial cell nuclei, and they are distinctly different for arteries and capillaries. The an gioarchitecture of the newt eye differs from that of brain in that hai rpin-shaped capillary loops are not observed at all.