GELATINE 



303 



are mounted in Canada balsam. The sections cannot be dehy- 

 drated in alcohol, because this will extract the stain from the 

 plastids. The following method may also be used: The mate- 

 rial is fixed in a solution of 5 gm. of corrosive sublimate in 100 

 gm. of absolute alcohol, which is acidulated with 10 drops of 

 hydrochloric acid. Then the fixative is removed by placing 

 the material in pure alcohol, which is several times replaced. 

 Sections from this material should be stained by immersion 

 for about twenty minutes in a solution of 20 gm. of acid fuchsin 

 in 200 c.c. of distilled water and 3 c.c. of aniline oil. They are 

 then washed in a mixture of 50 c.c. of a saturated alcoholic solu- 

 tion of picric acid and 100 c.c. of water until color ceases to be 

 given off from the sections. Then the picric acid is washed 

 from the sections in pure alcohol. The sections are next placed 

 in chloroform for ten minutes and are then ready to be mounted 

 in Canada balsam. 



AVhen desired, sections cut from fresh material may be fixed 

 and stained as above. Or the material may be fixed and im- 

 bedded, and after microtome sections have been cut- and mounted 

 on the slide they may be stained as above directed. 



A beautiful double stain for nuclei is prepared from acid 

 fuchsin and methyl blue as follows: The microtome sections 

 mounted on the slide are immersed for half an hour in a o.ooi 

 per cent, aqueous solution of acid fuchsin, then quickly washed 

 in water, and immersed for about one minute in a 0.002 per 

 cent, aqueous solution of methyl blue. The surplus stain is 

 then washed off in alcohol and the preparation is allowed to 

 dry; then the sections are immersed in olive oil from six to twenty- 

 four hours, after which they are washed in absolute alcohol 

 or in a mixture of absolute alcohol and xylol until the stains are 

 quite clear, and the preparation is ready to be mounted in Canada 

 balsam. 



Gelatine. — Motile swarm spores and the like are some- 

 times mounted for observation in a solution of gelatine, which 

 renders their movements less rapid, and in this way facilitates 

 the study of these bodies. About i gm. of gelatine is dissolved 



