104 CHAPTER IX. 



of workers) a mixture of equal parts of ether and alcohol ; 

 ToBBY (in Nature, November 17th, 1892, p. 51) advises a 

 mixture of four parts of ether and one of alcohol. Fish 

 advises acetone, see next §. Mann {Methods, etc., p. 172) 

 takes equal parts of ether and methyl alcohol. So also 

 Pavlow, Zcit. loiss. Mikr., xxi, 1904, p. 15. 



This stage may be omitted if the objects are of a suffi- 

 ciently permeable nature, and they may be brought direct 

 from alcohol into the collodion bath. 



159. The Collodion Bath. — The secret of success here is to 

 infiltrate the objects first with thin solutions, then with the 

 definitive thick one. (A thin solution may be taken to mean 

 one containing from 4 to 6 per cent, of celloidin [dried as 

 described in § 157] ; a thick solution, one containing 10 to 

 12 per cent.) 



If collodion be taken, the thin solutions may be made by 

 diluting it with ether. If photoxylin or celloidin be taken, 

 the solutions are made in a mixture of ether and absolute 

 alcohol in equal parts. 



The dried celloidin shavings dissolve very slowly in the 

 mixture. Elschnig {Zeit. viss. Mikr., x, 1893, p. 443), has 

 found that solution is obtained much quicker if the shavings 

 be first allowed to swell up for twenty- four hours in the 

 necessary quantity of absolute alcohol, and the ether be 

 added afterwards. 



BussB {op. cit., ix, 1892, p. 47) gives the following pro- 

 portions for the successive baths : — No. 1, 10 parts by weight 

 of photoxylin or p)erfectly dried celloidin to 150 parts of the 

 ether and alcohol mixture ; No. 2, 10 parts of photoxj'lin or 

 celloidin to 105 of the mixture; No. 3, 10 parts to 80 of 

 the mixture (already-used solution may be employed for 

 the first bath). 



I generally use only two solutions . one weak one, and one 

 strong one corresponding approximately to Busse's No. 2. 

 His No. 3 is so thick that excessive time is required to obtain 

 penetration by it. 



Mann (^Methods, p. 172) uses solutions of 2^ and 10 per 

 cent. 



Apathy (Behhens, Tahellen., 1898, p. 82) takes 2 per cent, 

 and 4 per cent, for the first baths, 8 per cent, for the last. 



