CHAPTER VI.
Special Staining Methods.—Special Methods for Staining the Nerve Centres.
1. For staining nerve fibres.
Three methods (two of which are modifications of the first) are employed far more often than any others. By these methods the myelin coating is stained. Tissues must have been hardened previously for many weeks in Müller’s fluid, or some other bichromate solution. They are then overstained in a solution of hæmatoxyline, and the section treated with a suitable bleaching reagent, when the colour is discharged from all the tissue elements except the nerve fibres. This method displays not merely the nerve fibres in the white matter, but also the fine network in the grey matter of the brain and spinal cord. Degenerated fibres are left unstained and so degenerated tracts shew up as unstained spots on a dark background. The sections may be subsequently stained with alum carmine or eosine to shew the cells and neuroglia.
Weigert’s method.—The piece of cord to be cut after prolonged hardening in Müller’s fluid is transferred without washing to absolute alcohol and dehydrated preparatory to embedding in celloidin (p. [30]). When sections are cut they are transferred at once to Weigert’s hæmatoxyline solution:—
| Hæmatoxyline | 1 | 4 | grains. |
| Alcohol | 10 | 45 | minims. |
| Distilled water | 100 | 1 | ounce. |
They are stained in this for twenty-four hours or longer, until they are quite black.
The staining will take place much more rapidly if the fluid be kept at 100° F. in the incubator. After staining they are transferred to Weigert’s differentiating solution:—