Magnetic Susceptibility of Beef Tendon

Abstract

That tendon fibers show marked mechanical and optical anisotropy has long been known. In addition to these properties, the magnetic anisotropy of tendon has been studied. Measuring the magnetic susceptibility of beef tendon parallel and perpendicular to the fiber axis, Wöhlisch 1 concluded that the tendon shows positive paramagnetic properties, i.e., the susceptibility is greater parallel than perpendicular to the fiber axis. His method was only qualitative, consisting of the observation of the rotation of the fiber freely suspended between the poles of a magnet, hence no numerical value for the susceptibility could be given.

While some degree of magnetic anisotropy is to be expected in such fibers it seems probable that, like most organic substances, they would be diamagnetic rather than paramagnetic. Gelatin, which is closely related to collagen, was found to be diamagnetic both in the dry form (Ambronn, quoted by Wöhlisch) and in approximately 1% solutions (Fallot 2 ). The susceptibilities obtained by the latter investigator ranged between −0.76 × 10⁻⁶ and −0.91 × 10⁻⁶

In Considering the cause of this apparent discrepancy it seemed possible that Wöhlisch' result may have been due to contamination of the material with traces of iron derived from the instruments with which the tendon was cut.

The magnetic susceptibility of iron at low field strength is of the order of 10³. One gram of diamagnetic substance of the susceptibility of 10⁻⁶ will appear to be paramagnetic, therefore, if the content of iron is higher than 10⁻⁹ g.

If a sample consisting of such a mixture of a ferromagnetic and a (presumably) diamagnetic substance is brought into a nonhomogeneous magnetic field, two forces will act (Curve B). However, Curve B shows saturation with increased field strength. A mixture of a diamagnetic and a ferromagnetic substance is characterized by Curve C.