Quantitative analysis of the cells of the cat's trigeminal ganglion.

The volume and structure of the perikarya of nerve cells in the trigeminal ganglia of adult cats were studied light and electron microscopically. According to their volume and eccentricity, the cells could be classified into three groups. Group I. Small cells. Their volume ranges up to 11,400 micrometer 3. Several of them stain light and are spherical in shape. Group II. Medium cells. Their volume ranges up to 40,00 micrometer 3. Several light-stained cells are seen among them. Group III. Large cells. Their volume is the range of 60,000 to 100,000 micrometer 3, and they are spherical in shape. Electron microscopically, the cytoplasm contains a well-developed rough-surfaced endoplasmic reticulum, numerous mitochondria, Golgi complexes, pigment granules, and interspersed neurofibrils and microtubules. The cells exhibit an ultrastructure varying in size and cytoplasmic density. In some cases, nerve fibres were in close contact with the cell body, but neither pre- nor post-synaptic thickenings could be observed.