In toto staining and preservation of peripheral nervous tissue.

A simple quantitative modification of the in toto staining technique for nervous networks of Sihler is described. The results are demonstrated on the innervation pattern of the hard palate of the rat. Formalin fixed hard palates of rat were macerated and bleached in an aqueous solution of 3% potassium hydroxide with a few drops of 3% hydrogen peroxide added. Thereafter, the specimens were decalcified in Sihler's solution I (1 part glacial acetic acid, 1 part pure glycerin and 6 parts 1% chloral hydrate), the process being controlled by radiography. The specimens were next stained in Sihler's solution II (1 part Ehrlich's hematoxylin, 1 part pure glycerin and 6 parts 1% chloral hydrate). After staining, the non-nervous tissues were destained in Sihler's solution I. Destaining was checked microscopically and was stopped before the finest branches of the nerves began to fade. The specimens were then washed in a weak aqueous solution of lithium carbonate and cleared in increasing concentrations of glycerin. Good visualization of nervous structures and a deep field of observation resulted; orientation of the peripheral nerves with respect to surrounding structures was readily seen and a three-dimensional image of the nervous networks was obtained.