CHAPTER IX. 97 



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. wiss. 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. 



BUSSE (op. cit., ix, 1892, p. 47) gives the following proportions for 

 the successive baths : No. 1, 10 parts by weight of photoxylin or 

 perfectly dried celloidin to 150 parts of the ether and alcohol mix- 

 ture ; 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 by it. 



MANN (Methods, p. 172) uses solutions of 2J and 10 per cent. 



APATHY (BEHKENS, Tabellen., 1898, p. 82) takes 2 per cent, and 

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



MYERS (Arch. Anat. Phys., Anat. Abth., 1902, p. 370) takes 1 per 

 cent., 6 per cent., and 16 per cent. 



See also NEUMAYER, Zeit. wiss. Mik., xxv, 1908, p. 38 ; DE VECCHI, 

 ibid., xxiii, 1906, p. 312 ; and FUHRMANN, Zeit. wiss. Zool., Ixxviii, 1905, 

 p. 524. 



FISH (Journ. Appl. Microscop., ii, 1899, p. 323) first infiltrates with 

 acetone (which he says may be used as a fixing and dehydrating agent 

 at the same time), then with a 4 per cent, solution of pyroxylin (gun- 

 cotton) in acetone, and, lastly, in an 8 per cent, acetone solution of the 

 same. See for other solutions 170 and 171. 



The objects ought to remain in the first bath until very thoroughly 

 penetrated ; days, even for small objects, weeks or months for 

 large ones (human embryos of from six to twelve weeks, for instance). 



When the object is duly penetrated by the thin solution, or 

 solutions, if more than one have been employed, it should be brought 

 into the thickest one. This may be done (as first described in this 

 work, 1st ed., 1885, p. 194) by allowing the thin solution to con- 

 centrate slowly (the stopper of the containing vessel being raised, 

 for instance, by means of a piece of paper placed under it), and 

 making up i;he loss from evaporation with thick solution. 



M. 



