LIST OF EEAGENTS, ETC. 383 



ride. One litre of water will dissolve about seventy grams 

 of mercuric chloride. 



12. Delafield's Hematoxylin. 



Use. — One of the best of stains for alcoholic material. 

 Must not be used until specimen has been freed from 

 any acids that may have been used in the process of 

 preservation. In staining add a few drops of the solu- 

 tion to distilled water until the desired depth of color is 

 obtained, then immerse the specimen. Dilute solutions 

 stain much more satisfactorily than concentrated, though 

 longer time is required. 



Preparation. — Dissolve four grams of hsematoxylyn crys- 

 tals in twenty-five cubic centimetres of ninety per cent, 

 alcohol. Saturate four hundred cubic centimetres of dis- 

 tilled water with ammonia alum ; to this add the first solu- 

 tion. Let the mixture stand exposed to the light and air 

 in an open bottle for three or four days ; then filter, and 

 to it add one hundred cubic centimetres of glycerine and 

 one hundred cubic centimetres of methyl alcohol. Let 

 the mixture stand for a time, then filter again, and keep 

 in a stoppered bottle. The stain works best if allowed 

 to ripen for two or three months before using. 



1 3. Dissectinff-Dishes. 



These may be of tin or earthenware. If the latter, ordi- 

 nary vegetable dishes will serve. A convenient tin dish 

 is a foot long, six inches wide on the bottom, seven or 

 eight inches wide on top, and two and one-half to three 

 inches deep. The bottom of the dishes should be cov- 

 ered by a layer one-quarter to one-half inch thick of 

 beeswax or paraffin which has been mixed with lamp- 

 black. A dark background is thus formed against which 

 the delicate tissues of the various specimens show well, 

 and the parts may be displayed by pinning them out on 

 the wax. It will be found that the pins will hold better 

 in beeswax than in parafiSn. Before pouring the melted 

 wax into the dishes, put into the bottom of each a num- 



