A RAPID PROCEDURE FOR STAINING NISSL GRANULES IN BRAIN TISSUE, TO BE USED FOR PHOTOMICROGRAPHY.

Although the sectioning of frozen brain tissue is generally regarded as a useful technique for inspecting certain topographic and gross morphologic changes in brains after experimental surgery, several shortcomings of this technique have led many experimental neurologists to utilize more time-consuming methods for preparing their brain specimens. For example, it is widely held that frozen sections stain rather poorly and, while they may be adequate for gross microscopic inspection, they are rarely of such quality as to provide a useful material for photomicrographic illustrations. In experiments which involve the study of various changes of the nerve cell body, the use of celloidin or paraffin embedded material has been regarded as imperative, because some artifacts, such as vacuolation of normal cells, usually observed in frozen material, make interpretations of the results difficult, if not impossible. In this laboratory it has been found, however, that frozen sections can be prepared in such a way that they are of comparable quality to celloidin embedded material in every respect. This involves dehydration of individual sections in various grades of alcohols before they are mounted. Such a dehydration shrinks the brain tissue rather uniformly. Mounting the sections in ethanol-gelatin mixture, although it introduces some hydration, does not cancel the effect of the previous dehydration. This procedure provides for a greater contrast among cells of various nuclear groups and, therefore, the material becomes adequate for a detailed microscopic analysis as well as photographic presentation. Vacuolation of normal cells can be usually avoided by soaking the brain specimen in 20% ethanol overnight before sectioning. The procedure is a rapid one; approximately a 3 1/2-hour period is sufficient for making the first section of a series available for microscopic study.