122 CHAPTER IX. 



soaked till thoroughly penetrated in ether,, or, which is 

 better, in a mixture of ether and absolute alcohol. DUVAL 

 (loc. cit.) takes for this purpose a mixture of ten parts of ether 

 to one of alcohol ; SCHIEF^EEDECKEB (and the majority of 

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

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

 mixture of four parts of ether and one of alcohol. But the 

 point is one of no great importance. FISH advises acetone, 

 see next . 



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. 



153. The Collodion Bath. The next step is to get the 

 objects infiltrated with thick collodion. The secret of suc- 

 cess here is to infiltrate them 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 cel- 

 loidiii [dried as described in 151] ; 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 cel]oidin 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. f. wis. M>ik , x, 4, 1893, p. 443) 

 states 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. On trial it seems to me that this is so. 



BUSSE (op. cit., ix, 1, 1892, p. 47) gives the following pro- 

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

 of photoxylin or perfectly dried celloidin to 150 parts of the 

 ether and alcohol mixture : No. 2, 10 parts of photoxylin 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 bv it. 



