52 Studies on the Neuroglia 



8. Cut sections and fix to slide or cover glass with albumin fixative. 

 To facilitate the application of this step, I may say that sections from 

 paraffin-imbedded tissues of the central nervous system are most readily 

 made by placing the knife at an angle of about 30° and placing a layer 

 of distilled water on the knife, renewing it constantly as necessity 

 requires. I have found no difficulty in cutting 3// to 5^« sections of the 

 spinal cord or even of the medulla of animals ordinarily used in the 

 laboratories. The sections are then caught on a small brush and floated 

 on distilled water contained in a small evaporating dish. When 40 to 50 

 sections have been cut and floated on the distilled water, the evapo- 

 rating dish is placed over a flame and the water is gently heated until 

 the sections flatten out, care being taken not to melt the paraffin. The 

 sections are then caught on cover glasses smeared with a thin layer 

 of albumin fixative and placed for 24 hours in the warm oven. 



9. Eemove paraffin and bring sections through alcohol into distilled 

 water. 



10. The sections are now placed for 24 hours in a mordant consist- 

 ing either of a 4^ solution of ferric alum or of a solution of liquor f erri 

 tersulphatis, made by adding one part of this to two parts of distilled 

 water. 



11. Sections are rinsed in two tap waters and one distilled water 

 and placed for 24 hours in a solution of sodium sulphalizarate, made by 

 adding to distilled water a sufficient quantity of a saturated solution 

 of sodium sulphalizarate in 70^ alcohol to give the distilled water a 

 sulphur-yellow color. 



12. Einse the sections in distilled water and dry between filter 

 papers. 



13. Sections are now stained for 15 minutes or longer in a 0.1;^ 

 solution of toluidin blue, which should be heated, after the sections are 

 in the stain, until the solution steams. Allow the stain to cool and 

 rinse sections in distilled water. 



The sections are next rinsed in a slightly-acidulated solution. For 

 this purpose Benda recommends primarily a 1^ aqueous solution of 

 glacial acetic acid, in which the sections remain for five to ten seconds 

 and are then dried between filter papers, hastily washed in absolute 

 alcohol and placed in creosote. This step was found necessary in stain- 

 ing the neuroglia of the frog, tortoise and dove. Benda further recom- 

 mends the use of acidulated alcohol, made by me by adding six drops of 

 hydrochloric acid to 100 ccm. of 70fo alcohol. This was found more use- 

 ful in differentiating the neuroglia of mammalia (dog, cat, rabbit), and 

 experience showed that the proper degree of washing was usually 



