32 BOTAi\ICAL MICROTECHNIQUE. 



other hand, it is the easier to obtain very thin sections the- 

 smaller the surface to be cut is. 



44. It is also in no respect unimportant what sort of paraf- 

 fine is used. I have used in most cases a paraffine recom- 

 mended by Altmann which melts at 58 to 60 C.* and is 

 obtained from the drug-store of Franz Wittig (Leipzig). But 

 when the size of the sections is more important than their 

 extreme thinness, as may be the case where one wishes a 

 general view, paraffine to which has been added more or less 

 of the superheated paraffine recommended by Count Spee is 

 more useful. Objects imbedded in this have the advantage 

 of rolling up much less easily during cutting. 



This superheated paraffine may be prepared by heating 

 ordinary paraffine in an open dish for one to six hours until 

 it has assumed a brownish-yellow color like that of yellow 

 wax, with the evolution of disagreeable white fumes, a slight 

 reduction of its volume, and the elevation of its melting 

 point. Recently such superheated paraffine can be ob- 

 tained directly from Dr. G. Griiblerf and others. 



45. In all cases a complete dehydration must precede the 

 transfer to paraffine. This can ordinarily be accomplished 

 by means of alcohol. Delicate objects are better not trans- 

 ferred directly from water to alcohol, in order to avoid col- 

 lapse ; but one of the methods for dehydration described in 

 14 to 17 may be used. In general it is sufficient to use 

 between water and alcohol a mixture of equal parts of both 

 fluids, in which the objects are left for an hour or longer. 

 Afterwards they are left in absolute alcohol from six to 

 twenty-four hours according to their size ; or even several 

 days, in some cases. 



46. From alcohol the objects are passed to a mixture of 



* [If paraffine of just this melting point cannot be obtained, it may be 

 readily prepared by mixing two paraffines of respectively higher and lower 

 melting points in proper proportions.] 



f [Dr. Grlibler's stains, mounting media, and other preparations, which. 

 are of standard excellence, may now be obtained of Eimer & Amend, Third. 

 Avenue, New York, and of the Franklin Educational Co., Boston.] 



