Blood vessels on Reissner's membrane were electron-microscopically fou
nd in 24 out of 30 rats of the Wistar strain. The vessels were noted i
n the upper turns, mainly in the third turn of the cochlea. They origi
nated from radiating arterioles in the upper spiral ligament and took
straight courses radially down to the spiral limbus, and further to th
e modiolus, running along the surface of the scala vestibuli side of t
he membrane. Their diameter was approximately 4 mum. Bifurcated blood
vessels were occasionally detected in 3 out of the 24 rats that posses
sed the vessels in the membrane. From the morphological point of view
the blood vessels in Reissner's membrane may possibly have some functi
on in the inner ear of the rat.