NERVOUS SYSTEM — OYTOLOGIOAL METHODS. 401 



771. Neurofibrils: Gold Methods. — Apathv's gold method, 

 § 371, gives perhaps the sharpest stain which has yet been 

 obtained — with certain invertebrates, but onli/ ivith these: 

 and even with these it is difRcalt and uncertain. 



JoEis {Bidl. Akad. Med. Belg., April 30th, 1904) gives the 

 following as being certain. Material fixed by the usual 

 methods is put for 8 to 12 hours into a 5 per cent, solution 

 of ammonium molybdate, then imbedded in parafRn. The 

 sections (fixed on slides by the water method) must be 

 washed for many hours or days in water. They are then 

 treated for about ten minutes with a r5 per cent, solution 

 of colloidi.il gold in water, rinsed and mounted. The stain 

 is permanent. 



The colloidal gold used was obtained from the Ohemische 

 Fabrik Heyden, in Radebeul- Dresden. It will dissolve in 

 about a day. 



772. ITeurofibrils, Molybdenum-Toluidin Blue (Bethe, Zeit. 

 tci-s. Mik., xvii, 1900^ p. 13). — Pieces of central nervous 

 system {of Vertebrates) are fixed for twenty-four hours in 

 niti'ic acid of from 3 per cent, to 75 per cent, strength, and 

 brought direct into alcohol of 96 per cent, for a day or more. 

 They are put for twelve to twenty-four hours into a mixture 

 of one part of ammonia (of sp. gr. 0'95) with three of water 

 and eight of 96 per cent, alcohol, then for six to twelve 

 hours into pure alcohol; they are then put for twenty-four 

 hours into a mixture of one part concentrated hydrochloric 

 acid with three of water and eight to twelve of alcohol, then 

 for ten to twelve into pure alcohol, and thence for not more 

 than two to six hours into water. They are now mordanted 

 for twenty-four hours in a 4 per cent, solution of ammonium 

 molybdate^ brought for 24 hours into alcohol, and imbedded 

 in paraffin {not celloidin). Sections are seriated on albumen 

 {withovt ivater), then passed through xylol and alcohol into 

 water, and " differentiated " — by which tbe author means 

 washed out — with water. About 1 to 1'5 c.c. of distilled 

 water should be poured on to the slide so as to form over the 

 sections a layer 1"6 to 2 mm. deep, and the slide is put for 

 two to ten minutes into a stove heated to not more than 55 

 to 60° C. The sections are then rinsed several times with 

 water, a solution of one part of toluidin blue in 3000 of 



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