Graf von Keyserlingk D, Schramm U
Anat Anz. 1984;157(2):97-111.
After perfusion fixation with a mixture of paraformaldehyde, glutaraldehyde, and potassium-chromate 4 adult human medullary pyramids were examined with the electron microscope. The myelin sheaths showed only mild signs of post mortal destructions. The periodicity of the lamellae is preserved and varies about 17 nm. For quantitative purposes specimens were taken at random from regions with an extend of half a mm2 on the cross section of the pyramid. On the average 62 lamellae (s = 5, n = 200) built up 1 micron myelin sheath in the 4 brains. The myelin sheath thickness and the inner circumference of the myelin sheath are measured. The axon diameter is calculated from the inner circumference. We obtained an average number of 66,000 fibres, s = 11,000 per mm2. Fibres with a total diameter below 4 microns amount to 87.9%, fibres from 4 to 10 microns to 10.77%, and larger than 10 microns to 1.4%. An axon diameter of about 0.5 micron combined with a thickness of the myelin sheath of 0.3 micron was most often found in all 4 cases. The fibres showed a broad variation of myelin thickness. In a given group of the small axons the thickest myelin sheath exceeded 3 to 4 times the value of the thinnest one. The coefficient of correlation between axon diameter and myelin sheath thickness was calculated as r2 = 0.56. No correspondence exists between frequency maxima and the ratio g, axon diameter to total diameter. Below a total fibre diameter of 5 microns the ratio g scatters broadly about 0.6, fibres larger than 5 microns exceed the value of 0.6. From the morphological data only large sized fibres can evoke a strong effect on compound action potentials if the method of reconstruction of the action potential from fibre size frequency distribution is employed.
用多聚甲醛、戊二醛和铬酸钾的混合液进行灌注固定后，对4个成人的髓质锥体进行了电子显微镜检查。髓鞘仅显示出轻微的死后破坏迹象。板层的周期性得以保留，约为17纳米。为了进行定量分析，从锥体横截面上面积为0.5平方毫米的区域随机取样。在这4个大脑中，平均62层板层（标准差s = 5，样本数n = 200）构成1微米厚的髓鞘。测量了髓鞘厚度和髓鞘内周长。根据内周长计算轴突直径。我们得到平均每平方毫米有66,000根纤维，标准差s = 11,000。总直径小于4微米的纤维占87.9%，4至10微米的纤维占10.77%，大于10微米的纤维占1.4%。在所有4个病例中，最常发现轴突直径约为0.5微米，髓鞘厚度为0.3微米。这些纤维的髓鞘厚度差异很大。在一组给定的小轴突中，最厚的髓鞘超过最薄髓鞘的3至4倍。轴突直径与髓鞘厚度之间的相关系数计算为r2 = 0.56。频率最大值与g值（轴突直径与总直径之比）之间不存在对应关系。在总纤维直径小于5微米时，g值大致分散在0.6左右，大于5微米的纤维超过0.6的值。从形态学数据来看，如果采用从纤维大小频率分布重建动作电位的方法，只有大尺寸纤维才能对复合动作电位产生强烈影响。
