To obtain well preserved, well stained samples of cells of the spinal fluid would seem a simple feat. In fact, only through the development of a very laborious technic have workers in the past achieved success. The difficulty has been that if a drop of spinal fluid is placed on a slide and allowed to dry in air, so much shrinkage of the cells occurs, and so much deterioration, that sharp staining and exact differentiating are quite impossible. Acceleration of the drying with heat causes even worse alteration than drying at room temperature. Nor can a fluid fixative be added for fear of washing away the freely floating cells.
Alzheimer overcame these difficulties by adding to several cubic centimeters of fluid a large volume of alcohol, centrifugalizing it until a coagulum formed at the bottom of the tube, embedding the coagulum in celloidin and cutting sections. This elaborate technic sometimes