INTRODUCTION. 



ta Hpnce it is impossible to lay down rules 



to S eaL in whic'h tissues are to be stained : 



The staging of the nucleus, however, can be readily secured by 



fle explicit directions given in the chapter on " Cell- 



^ 79 tU Of the whole class of staining agents, it may be said that 

 exposure to strong light diminishes the brilliancy of the coloring 

 they Foduce in the specimen, and in many cases complete y 

 destroys it In general, the staining obtained by allowing the 



*. * S for a long time in a <lilu ? solution , 



dye is more satisfactory than when a stronger dye is use< 



e> CARMIN. Two grades are readily procurable in this coun- 

 try ; 'namely, (1) " No. 40," (2) Orient." The former is the 

 cheaper and will answer for all cases described in this treatise ; 

 but attention must be called to the fact that it is sometimes 

 adulterated, and hence it may be found necessary to change the 

 proportions given in the following formulas. A good carmm, 

 even of the grade first mentioned, should leave only little residue 

 when placed in strong ammonia. If more than a trace of resi- 

 due is found, the amount of carniin in the formula must 

 proportionately increased. 



81. Ammonia-carmin. Pure powdered carmin is rubbed 

 up with a little water to form a thin paste, enough strong am- 

 monia to dissolve it is cautiously added, and the whole is then 

 filtered. The filtrate is to be evaporated slowly over a water- 

 bath. The dried mass dissolves readily in water, forming a 

 clear liquid which keeps well ; but it is better to preserve the 

 mass in a tightly-stoppered bottle, dissolving it only as required 

 (Hartig's carmin). 1 



82. A modification of this carmin is made as follows: .2 to 

 .4 gram of carmin is shaken up with 80 c. c. of water, and a 

 few drops of ammonia added. A part of the carmin dissolves, 

 and is to be filtered. If the filtrate smells strongly of ammo- 

 nia, it is allowed to stand for half a day under a bell-jar. A 

 drop of ammonia will re-dissolve any slight trace of carmin 

 which may separate. This fluid is to be added to water, drop 

 by drop, until the right color is obtained (Gerlach's ammonia- 

 carmin). 2 



83. If, to the filtrate last mentioned, 30 grams of glycerin 



1 Uippel : Das Mikroskop, i. p. 284. 



2 Behrens-.Hilfsbuch, p. 257. 



