The Microscope. 239 



The sections to be stained, having been bleached and washed 

 in the manner already described, must, after a short preliminary 

 soaking in alcohol, be placed in the tannic fluid for about one 

 minute, and thence transferred to the green dye for three min- 

 utes, upon the expiration of which time they are to be rapidly 

 washed in distilled water, and immediately passed into the car- 

 mine fluid, there to remain for from three to four minutes, then 

 rinsed in dilute acetic acid (5 drops of glacial acetic acid to 1 

 ounce of distilled water), again rapidly washed in distilled wa- 

 ter, and finally transferred to clean methylated spirit. Let them 

 remain in this for five minutes, pour off the alcohol, and replace 

 by fresh spirit ; allow the sections to remain in this another five 

 minutes, and afterwards transfer to oil of cajuput. In ten min- 

 utes pour off the oil of cajuput, and replace by turpentine, in 

 which they should be allowed to soak for five minutes, when the 



sections are ready for mounting in balsam. It must be noted 

 that the times given above are only approximations, and will 

 not hold good for all cases, since the time required for the action 

 of the stain is materially modified by the thickness of the sec- 

 tion, and by its physical structure, and very possibly also by its 

 chemical constitution. It will be found in practice, that, for the 

 general run of wood sections, very little variations from the times 

 indicated will be required. When an alteration in this direction 

 is necessary, it will be within very narrow limits, and to carry 

 it out successfully will not tax either the ingenuity or the pa- 

 tience of the experimenter very severely. Wood sections stained 

 by this method make beautiful preparations. Not only are cer- 

 tain portions of the sections dyed green and crimson respective- 

 ly, but other portions acquire various intermediate tints, so that 

 certain sections of much diversity and complexity of structure, 

 when stained by this method, rival in splendor some of the dia- 

 toms. We will give a few examples of pretty botanical sec- 

 tions : — 



Orange Peel, common object though it be, is not to be 

 despised by the microscopist. Transverse sections must be pre- 

 pared by the gum method. These sections are not to be sub- 

 jected to the action of alcohol ; but after drying between glass 

 slips, soak them in turpentine and mount in balsam. We shall 

 then have a good view of the large globular glands whose office 

 it is to secrete the essential oil, upon which the odour of the 

 orange depends. Sections may also be bleached, and stained 

 with carmine and aniline green as before mentioned. 



Sponge may readily be cut after being tightly compressed 

 between two pieces of cork, or its interstices may previously be 

 filled up by immersion in melted paraffin or mucilage, and sec- 

 tions cut in the usual manner. 



