[19] PRESERVATION OF MICROSCOPIC MATERIALS. 625 



sectionized as follows: From absolute alcohol it is traDsferred to oil of 

 cloves or laveuder, and then to pure paraffine, brought just a very little 

 above the melting point. 



C. Weigerfs rapid method of hardening the spi7ial cord. — Mdller^s fluid 

 hardens the spinal cord in about eight weeks at ordinary temperatures, 

 but this may be accomplished eight to ten days if the hardening is done 

 in a warm chamber or oven kept at about 120"^ F. While this is in prog- 

 ress camphor water should be added to prevent the development of 

 putrefactive organisms. 



The hardening may be still more rapidly done if ErlicWs fluid is used. 



This consists of — 



Potassium bichromate 2^ per cent. 



Copper sulphate ^ " 



With the aid of heat this hardens the spinal cord in four days, with- 

 out heat in eight to ten days. 



The sections are stained with acid fuchsin* which is used as follows : 

 The sections, not to exceed .025 mm. in thickness, are placed for one hour 

 in a saturated solution of acid fuchsin, but the staining is greatly modi- 

 fied by the subsequent treatment, as the diffusely stained sections are 

 next transferred to a large watch-glass and washed in water. They are 

 then transferred to a third watch-glass and washed in the following so- 

 lution : 



One huudred cubic centimeters of absolute alcohol. 

 One gram of caustic potash. 



This is allowed to stand for twenty-four hours, until the alcohol is sat- 

 urated with the alkali. Ten cubic centimeters of this mixture are added 

 to every 100 cubic centimeters of absolute alcohol, and in this mixture 

 the colored sections are washed. This washing out process is the most 

 important thing in the application of the method. As soon as the sec- 

 tion is transferred to the alkaline alcohol on a spatula a cloud of the 

 red coloring matter is set free. The section is then geutly shaken, and 

 as soon as the limits of the gray matter are defined it is transferred to a 

 large watch-glass full of clean water. This last wash must contain no 

 traceof acids; thetracesof alkaliuealcoholadheringto thespatula will do 

 no harm, and the section must be washed in it till no more clouds of color 

 are given off'. It is then transferred to a fifth wash of clean water, when 

 the operator should notice if the gray portions are the lightest. If this 

 is the case and the section is still red the process has been successful. 

 If the section is too pale it must be restained ; or if the gray substance 

 is not differentiated by a paler tinge it must be returned to the alkaline 

 alcohol and then again washed in clean water twice in succession. The 

 sections then dehydrated and treated in the usual way with clove oil 

 and mounted in Canada balsam. Sections which have been embedded 

 in celloidin should be treated with xylol instead of oil of cloves, and 



* Fuchsin S. No. 130, made iu the Baden Aniline and Soda Manufactory, may be ob- 

 tained in small quantities from Dr. Griibler, Leipzig, 17 Dufour strasse. 

 S. Mis. 40 40 



