BRIEFER ARTICLES 



PARAFFIN SOLVENTS IN HISTOLOGICAL WORK 



In the last few years there have been described in .the Botanical 

 Gazette two ways of improving the common method of replacing 

 xylol with paraffin in histological work. The alleged defect in the old 

 method lies in the fact that the paraffin sinks to the bottom of the vessel 

 and immediately surrounds the specimens with a concentrated solution. 

 Land's" remedy for this is to support the paraffin near the surface of 

 the xylol in a basket of wire gauze; Goodspeed^ molds the paraffin 

 into a lump that will fit the containing vessel and rest on top of the 

 xylol. Both of these methods have been found good for accomplishing 

 the end desired, and a third may be of interest. 



The paraffin to be used can, by aeration, be rendered capable of 

 floating in xylol, the method of preparation being similar to that 

 employed in giving buoyancy to some kinds of soap. While the paraffin 

 is at a temperature only a degree or two above that required for melting, 

 a current of cold air is bubbled through it, causing it to harden as a 

 frothy mass. This mass is then kneaded to secure finer grain and 

 more even distribution of the air bubbles. Only a small amount of 

 air is needed to produce the proper buoyancy, and it can be supplied 

 from any one of numerous sources and cooled by passing through a 

 condenser. Although the method may seem troublesome, it is really 

 not so; a large amount of paraffin may be prepared at one time, and 

 nothing further is necessary to get the desired results. 



Although this method of holding the paraffin at the top of the 

 xylol has been found successful and easy of manipulation, I do not 

 employ it as a rule, because I have not yet seen the defect of the old 

 method of adding the paraffin when xylol is used, and chloroform has 

 been found perfectly satisfactory in all cases. If, when xylol is used, 

 the necessary amount of paraffin be added in a finely divided con- 

 dition in 5 or 6 portions, and diffusion aided by gentle agitation, a 



'Land, W. J. G., Microchemical methods, an improved method of replacing the 

 parafl&n solvent with paraffin. Box. Gaz. 59:397. 1915. 



* GooDSPEED, T. H., Method of replacing paraffin solvent with paraffin. Box. 

 Gaz. 66:381-382. 1918. 



305] [Botanical Gazette, vol. 68 



