G. Carl Huber 53 



attained by dipping the sections into this solution as many times as 

 there were micra in the thickness of the section. Tne further pro- 

 cedure is as above. 



15. The sections are differentiated in creosote. Benda states that 

 the sections are properly differentiated after they have remained in 

 the creosote about ten minutes. In my work, however, the time varied 

 from about ten minutes to several hours. Sections washed in acidulated 

 alcohol are usually differentiated in about ten minutes ; sections washed 

 in the dilute acetic acid solution require a much longer time, varying 

 from one to several hours. It is therefore necessary at all times to 

 control the differentiation under the microscope. 



16. After differentiation in the creosote the sections are dried 

 between filter papers, washed in several xylols and mounted in xylol- 

 balsam. 



To the naked eye, preparations well differentiated should have a 

 bluish-red or brownish-red color, large masses of neuroglia showing as 

 blue areas. Under the microscope, the neuroglia fibers appear stained 

 deeply blue and stand out very distinctly. The chromatin of the neu- 

 roglia cell nuclei presents a purplish-blue color; the remainder of the 

 nucleus is brownish-red and the protoplasm is of the same color, but 

 of a lighter hue. The myelin and neuraxes of the nerve fibers are of a 

 brick-red or brownish-red color, the neuraxes staining much more 

 deeply than the myelin. The nerve cells are of a brownish-red color, 

 the chromophile substance staining more deeply, and the nucleoli are a 

 deep purplish-blue. The fibrous connective tissue stains a pink-red, 

 its nuclei a purplish-blue. The red-blood cells are of a dark greenish- 

 blue. The colors here given are those seen in a well-differentiated 

 preparation, especially after washing in acidulated alcohol (step 14). 

 In case the acetic acid wash is used, the myelin and neuraxes retain 

 some of the blue color, giving them a reddish-purple or even a bluish 

 tinge, the axis-cylinders staining more deeply; even in such prepara- 

 tions, however, the neuroglia fibers may be clearly made out by reason 

 of their deep blue color. It is necessary to add that it is not always 

 possible to obtain a clear differentiation, as the method while often 

 reliable, is not without its whims. It is my custom to fix as many sec- 

 tions to one cover glass as I can, and nearly always some of the sections, 

 if not all, will show the desired result. In over-differentiated pre- 

 parations, the neuroglia fibers have a brownish-red color, but may 

 usually be clearly seen. Such preparations may, after removal of the 

 creosote and xylol, be brought into water and then stained again in 

 toluidin blue, the further treatment being as above described. 



