The optical properties of vertebrate nerve axons as related to fiber size

✍ Scribed by Schmitt, Francis O. ;Bear, Richard S.

• Publisher: Wiley (John Wiley & Sons)
• Year: 1937
• Tongue: English
• Weight: 680 KB
• Volume: 9
• Category: Article
• ISSN: 0095-9898
• DOI: 10.1002/jcp.1030090209

✦ Synopsis

Since the early work of Valentin (1861) much information about the ultrastructure of nerve has been obtained by means of polarization optics (for reviews, see Schmidt, '24, '34).

Most of this work has concerned itself with the structure of the myelin sheath. The optical properties of the myelin sheath lipoids were interpreted by Klebs (1865) as indicating the presence of positive uniaxial crystallites oriented with optic axes extending radially. Viewed laterally medullated fibers appear, therefore, negatively birefringent with respect to their long axes. This negativity is a fairly certain criterion of the presence of myelin in any types of nerve fibers which show it.

Ambronn and Held (1895) compared the osmic acid and Weigert techniques with that of the polarization optics and found the latter far superior for the detection of myelin and for revealing the finer nuances of organization of the myelin. Recent work from Diamare's laboratory (see particularly Cristini, '28, and Mezzino, '31) and by Schmidt ( '35, '36) has directed attention to the role of the protein elements in determining the structure of the myelin sheath. The high degree of organization of this sheath is shown perhaps most strikingly by the x-ray diffraction analysis (Schmitt, Bear and Clark, '35). Almost without exception the past work on nerve birefringence has been of a purely qualitative nature.