398 CHAPTER XXXI I. 



drops of acetic acid and five of 1 per cent, gold chloride, and fixes with 

 hyposulphite of soda of 5 per cent. 



LIESEGANG (Kolloidchcmie, Beihefte, iii, 1911, H. 7 ; Zeit. wiss. Mik., 

 xxviii, 1912, p. 369) makes sections of formol material by the freezing 

 process, and silvers them until yellow. He then adds to the silver bath 

 an equal volume of 50 per cent, solution of gum arabic and the same 

 amount of saturated solution of hydroquinoii. After one or two min- 

 utes the sections are brought into 10 per cent, solution of hyposulphite 

 of sodium, washed and mounted. Results said to be the same as by the 

 usual process. 



770. BIELSCHOWSKY'S Methods (BIELSCHOWSKY and WOLFF, 

 Biol. Centralb., xxv, 1905, p. 683). Objects of not more 

 than 2 mm. in thickness are fixed in neutral formol of 6 to 10 

 per cent, (time not stated), washed out well with distilled 

 water, and put for at least two days into nitrate of silver of 

 2 per cent, in the dark. Wash for a few minutes, and put 

 for half an hour to several hours into a bath made as 

 follows : To nitrate of silver of 10 per cent, add drop by 

 drop 40 per cent, solution of caustic soda until no further pre- 

 cipitate is formed (this will be about 5 drops to 10 c.c.), 

 dissolve the precipitate almost entirely in just enough 

 ammonia, filter and add 4 to 5 vols. of water. The solution 

 will on'ly keep for a few hours. After this bath, wash again, 

 put for 1 to 6 hours into formol of 4 to 5 per cent., dehydrate 

 and bring through xylol into paraffin. Sections are toned 

 on the slide for 1 to 2 hours in chloride of gold of one tenth 

 to one twentieth per cent, (which it is well to neutralise with 

 lithium carbonate), rinsed, fixed for 5 to 15 minutes in hypo- 

 sulphite of soda of 5 per cent., washed for 6 to 12 hours in 

 running water and mounted in balsam. 



If nuclei take the impregnation, the fibril stain will not 

 have succeeded, but there may be a useful stain of other 

 elements, especially tigroid matter. 



SCHLEMMER (Zeit. wiss. Mik., xxvii, 1910, p. 22) makes the 

 oxide bath by adding the caustic soda in excess, and washing 

 the precipitate by repeated decantations until the wash water 

 no longer gives an alkaline reaction, takes it up with ammonia 

 and filters through spun glass, and thus obtains a solution 

 which will keep for several days. I find the filtering is not 

 necessary. 



For older forms of this method see last ed., and Neur f 

 Ceutntlb., xxiii, 1903, p. 977, and xxiv, 1904, p. 387 (the 



