APPENDIX. 371 



freezing agent; Swift's ether freezing microtome 

 may be used. 



STAINING. 

 Haematoxylin. 



a. 1. Kleinenberg's hcematoxylin. Take crystallized cal- 

 cium chloride, and add it in excess to 70 per cent, 

 alcohol ; shake well and let it stand. Draw off the 

 saturated solution and add alum to excess, shake up 

 and let stand for a day. Filter. 



2. To one volume of the nitrate from (1) add six to 

 eight volumes of 70 p.c. alcohol. 



3. To the mixture thus obtained, add drop by drop a 

 saturated solution of haematoxylin in absolute alco- 

 hol, till it is a moderately dark purple. 



The solution will become considerably darker after 

 some days. It is better to make it some weeks, 

 or even months, before it is required for use. 



It may be diluted to any extent required with the 

 mixture (2). If a section is placed in haematoxylin 

 for some time it must of course be covered up, or 

 the spirit will evaporate, and the solution become 

 concentrated. In many cases it is well to stain 

 a piece of tissue as a whole in haematoxylin before 

 imbedding, in this case the tissue should be left in 

 the diluted fluid one to two days; a tolerably porous 

 tissue naturally serves best for this method. A 

 small piece only should be taken. 



242 



