Morphometric studies on the relationship between myelin sheath and axon area in the sciatic nerve of adult rats.

The myelin sheath and axon areas in the sciatic nerve of 20 adult rats were studied using the video-point-counting method (Quantimet). This automatic measurement procedure allows an exact and rapid determination of the above mentioned areas as a result of the differing intensities of the structures. The electron-microscopic pictures are projected at a magnification of 3500 onto the monitor through a lens system from a Vidikon-TV-tube, objective 32 mm. The areas of single nerve cross-sections, myelin sheath areas and total area are then measured. These area values are stated in picture points which can be calculated to absolute values. The statistical evaluation of both parameters shows a linear regression with a correlation coefficient of 0.94. These values are compared with the results obtained using the conventional manual methods of other authors, e.g. determination of lamellae number or myelin sheath thickness as well as axon circumference or axon diameter. The special advantages of this procedure are thereby pointed out.