Mineral Distribution in Some Nerve Cells and Fibers. ∗

Abstract

It is known from examination of many types of tissue that Mg and Ca, as revealed by the electron microscope, is located in areas which show white ash following microincineration. In nerve tissue certain difficulties have hampered a direct study of Ca and Mg by means of the electron microscope. Some of the findings in incinerated sections of frog sciatic and sympathetic ganglia are believed to be of significance although we have not been able to identify the salts as clearly as is desirable.

When sections of frozen and dehydrated (Scott and Packer 1 ) frog sciatic are carefully incinerated and examined by dark field (Scott 2 ) the large myelinated fibers at the periphery of the nerve leave residues of white ash probably consisting largely of Ca and Mg. The ash is clearly the remains of the myelin sheath as it corresponds almost exactly with stained preparations of the same nerve taken a few levels either above or below. The point to emphasize, however, is that there is no visible residue of any sort in the tissue spaces surrounding the nerve fibers.

In sharp contrast to plentiful mineral in the nerve fibers and little if any in the tissue space is the picture obtained when sympathetic ganglia are incinerated following the same treatment. The sympathetic ganglion cells are recognizable by their residue. Nuclear, nucleolar and Nissl substance ash is dense and of the variety associated with the presence of Ca and Mg. There is as a general rule a wide band, varying from an eighth to a sixth of the cell diameter, of dense white ash concentrated at the periphery of the cell. The tissue spaces immediately about the ganglion cells are filled with mineral residue not unlike, in quality and quantity, that seen in the neurones.