Fibre Population of the Vestibulocochlear Anastomosis in the Cat

Olivocochlear fibres were studied by light and electron microscopy in the microdissected vestibulocochlear anastomosis of adult cats. The anastomosis was found to contain at least two types of fibres--one myelinated variety with mean axonal diameter 1.7 micron and numbering 498; the other, an unmyelinated variety, with mean axonal diameter 0.4 micron and numbering 868. The average total number of axons was 1356. The ratio of unmyelinated to myelinated axons was usually about 1.5, with a single cat having a bilateral ratio close to 3.5.