INTRODUCTION. 11 



From this it is to be transferred to glycerin, where it soon 

 becomes clear. 1 



50. Calcic hypochlorite in aqueous solution bleaches many 

 tissues without the use of an acid, but, in general, specimens 

 which have been subjected to its action are more thoroughly de- 

 colorized if they are subsequently placed in dilute hydrochloric 

 acid, washed in pure water, and finally transferred to glycerin. 

 Preparations which have been bleached by this method are easily 

 colored by some of the staining agents described on page 15. 

 Sodic hypochlorite may replace it in all cases. 



51. Carbon disulphide is used as a solvent for fats. 



52. Carbolic acid, or phenol, dissolved in the least quantity 

 of concentrated hydrochloric acid which will take it up, gives 

 a green color with lignitied cells. It is better to add to a few 

 drops of the strongest hydrochloric acid a small quantity of 

 crystallized phenol, warm the mixture slightly, and upon its 

 cooling add enough acid to remove any cloudiness. 



53. Chloral hydrate in aqueous solution is recommended by 

 Arthur Meyer- as a clearing agent. Two parts of water are 

 added to five parts of chloral, and used somewhat above the 

 temperature of 15 C. 



54. Chromic acid. The pure acid, in strong solution, acts 

 promptly on cell-walls, dissolving all except those which are 

 silicified and those which are cutinized. Even the latter yield 

 to prolonged action. If the solution is more dilute, the action 

 goes on only so far as to cause swelling of the cell-wall, bring- 

 ing out, in special cases, a very distinct stratification. Solutions 

 which are so dilute as to be merely pale yellow cause hardening 

 of soft tissues, and this acid therefore forms an excellent adju- 

 vant to alcohol for this purpose (see Part II.). 



55. Cuprammonia. To a solution of cupric sulphate add 

 enough soda (or potassa) to produce a precipitate. After 

 removal of the excess of liquid by filtration, place the precipitate 

 in a flask, wash once with water \vhich has been freed from air by 

 boiling, and then dissolve the mass in the least quantity of con- 

 centrated ammonia which will take it up. The freshly prepared 

 solution should act promptly on delicate fibres of cellulose, 

 cotton for example, causing them to swell and apparent! \ pass 

 into solution. Lignified and cutinized cell-walls are not acted 



1 Flahault : Accroissement terminal de la racine. Ann. des Sc. nat., 187.S, 

 vi. p. 24. 



2 Das Chlorophyllkorn, Leipzig, 1883. 



