Gh THE MICROSCOPE. 
Selections. 
Rapip Microscopic Mountinc.—Among the most important 
of the recent improvements in microscopical manipulation are the 
methods for mounting. specimens in consecutive order. For this 
purpose the specimen is imbedded in paraffin, the hardness of which 
varies according to the temperature. In wintera softer paraffin 
must be used than in summer. Experience alone can teach one the 
exact consistency necessary. The specimen must be thoroughly 
impregnated with the paraffin as it has to withstand the desiccating 
effect of the air when exposed in thin sections. This may be 
accomplished in several ways. The specimen is hardened by any 
desired manner and placed in absolute alcohol. From this it is 
transferred to turpentine, or a saturated solution of paraffin in 
turpentine, benzole or chloroform. After the alcohol has been 
completely expelled the object is placed in melted paraffin of a low 
grade and kept there for a considerable time, varying, according to 
the size of the specimen, from half an hour to several hours. Then 
it is imbedded in the imbedding paraffin in the usual manner. 
After cooling, the paraffin is trimmed to fit the microtome, 
which must be one of the various forms of the “sledge microtome.” 
Then the portion of the paraffin containing the object is trimmed to 
a square slightly larger than the specimen, and placed with one of 
its sides at right angles to the line of the stroke. The knife of the 
microtome is also placed at right angles to the same line so that the 
stroke is direct and not a particle “drawing.” 
The cutting is now done inthe usual manner but with a dry 
razor, and if the paraffin is of the right consistency, the sections will 
not adhere to the knife nor curl but will form a ribbon, the edges of 
the sections of paraffin adhering to each other so that they form a 
ribbon. After cutting a small portion, the ribbon is removed and 
placed under a bell-glass to prevent being blown away by an acci- 
dental draft of air. The cutting is continued until the specimen is 
entirely converted into sections. Unless both edges of the paraffin 
block are parallel to each other and to the edge of the razor the 
ribbon will not be formed. 
The slides used also require preparation. There are two methods 
in use, each having its advantages. The first described employs lac. 
Bleached lac is dissolved in creasote or absolute alcohol. This is 
best accomplished by employing freshly bleached lac; though, if this 
