Scarpa's ganglion in the cat.

A quantitative analysis of characteristics of neurons in Scarpa's ganglion was performed with light and electron microscopy. Plotting the major axes of 340 neurons as a function of their nuclear diameters indicated that there are two types of cells: Large neurons with large nuclei and small ones with small nuclei. Small neurons have an excentric nucleus with indentations of the nuclear membrane. Large neurons have a spherical and central nucleus. Almost all cells are myelinated. Occasional unmyelinated cells or those surrounded by many myelin layers represent normal variations of large or small neurons. The inferior portion of the ganglion containing about one-third of the total number of neurons and innervating most of the saccular macula and the posterior crista has more than 10% small neurons. The superior portion of the ganglion with two-thirds of the total number of neurons and innervating the remaining sensory epithelia has about 5% small neurons. The significance of this observation concerning innervation patterns of vestibular sensory epithelia is discussed.