Comparison of Weigert Stained Sections v Sections for Study of Myelin Sheaths

Myelinated fibers can be demonstrated in thin unstained brain sections of freshly killed uninjected animals. With this method myelinated fibers stand out as clearly as in stained Weigert sections from formalin- fixed brains. Unstained unfixed sections can be viewed under ordinary light within minutes after death of the animal and immediately photographed for permanent records. Such sections have value for neuroanatomical studies, and for rapid localization of various types of experimental lesions. A variety of methods are used for staining myelin sheaths of central and peripheral axons. These techniques include the Weigert, Woeleke, and Weil methods, all of which depend on the use of fixed stained tissue and necessitate a processing time of several weeks. For many years we have used a simple and rapid method for showing myelin in experimental material-chiefly for quick localization of experimental lesions but also for neuroana- tomical studies. This technique uses frozen sections of brains of freshly killed uninjected rats. The sections are viewed at once under a microscope and photographed. This method depends on use of a very quick embedding medium (Ames OCT Compound), a cryostat, and a combined microscope and camera (Zeiss Ultra Phot II) which makes possible immediate viewing and photographing of the sections. Such sections compare very favorably with those obtained with any of the