260 PRACTICAL MICROSCOPY. 



before being stained. The bleaching solution is made by 

 mixing \ oz. of chloride of lime with a pint of water, 

 shaking occasionally for an hour, and after allowing the 

 sediment to subside, decanting the clear solution. The 

 process of bleaching should be carefully watched and 

 stopped when complete. Tissues vary so much in colour 

 and density that no fixed time can be given for bleaching 

 them. Very thorough washing is necessary. The elimina- 

 tion of the chlorine will be much facilitated by placing the 

 sections, after removal from the bleaching liquid, in a solu- 

 tion of sulphite of soda (i drachm to 4 oz. of water) for an 

 hour, then washing the sections by soaking them for at least 

 six jor eight hours in water, changing occasionally, and 

 finishing with distilled water. If they are not to be stained 

 at once, they should be preserved in water containing 

 20 per cent, of alcohol, as when kept in water only, in the 

 course of two or three days they become covered with a 

 peculiar fungus growth. At this stage all air-bubbles 

 should be removed from the tissue. This is conveniently 

 done by placing the sections in dilute alcohol, putting them 

 under the receiver of an air-pump, Fig. 222, and exhausting 

 the latter, repeating the pumping occasionally so long as 

 air-bubbles are given off. For this purpose a small tube 

 bottle is employed about ij inch long, and a receiver just 

 large enough to hold it, the process being thus rendered a 

 rapid one. 



Where it is required to uniformly stain the section in 

 order to render prominent the more delicate cell walls, 

 logwood answers exceedingly well and is very permanent. 



LOGWOOD SOLUTION. 



Logwood, in coarse powder . . 2 oz. 



Distilled water 10 oz. 



Boil for half an hour in a glass beaker, replacing what is 

 lost by evaporation ; strain, and to each ounce of liquid 



