80 MICROSCOPICAL TECHNIQUE. 



into the melted soft paraffin, and when this has become firm the 

 surfaces are again trimmed square. The reason for this very 

 special care is that any curve in the ribbon of sections produced 

 by neglect of this precaution is accentuated by the flattening out of 

 the sections. The ribbon is then divided, and one end is seized 

 with forceps and the other end is gently lowered on to the surface 

 of the warm water. When the flattening is complete, a slide is 

 immersed in the water, and the ribbon is floated to its position 

 with a stiff brush. As much of the water as possible is then 

 drained off, and the rest evaporated by placing the slide on the top 

 of an oven where the temperature is just below the melting point 

 of the paraffin. When the water has evaporated completely, the 

 opacity of the sections disappears, and they become much more 

 transparent and look dry. When the fixation is quite com- 

 plete, the paraffin is melted by putting the slide inside the oven 

 for a little while, and is then washed off with turpentine or xylol. 

 One of the great advantages of this method is the perfect ease and 

 safety with which it allows sections on the slide to be uianipulated, 

 so that the most various stains and reagents can be applied suc- 

 cessively to a slide. Of course, a single section can be mounted 

 in the same way, and, when desirable to examine a few sections 

 with as little delay as possible, warm methylated spirit, or even 

 absolute alcohol, evaporate more rapidly than water, while the fixa- 

 tion is as perfect with them and the method of use exactly the 

 same, as with the less volatile liquid. 



Method for making Paraffin Sections from Preparations 

 stained with Ehrlich's Methyl en-Blue.*— In the course of his 

 work Mr. G. H. Parker found it necessary to devise a method for 

 making paraffin sections from preparations in which the nervous 

 elements had been stained with Ehrlich's methylen-blue, of which 

 he now gives the following account : — " In order to stain the ele- 

 ments in the nervous system of a crayfish, i/ioth to i/2oth ccm. 

 of a '2 per cent, aqueous solution of methylen-blue was injected 

 into the ventral blood sinus, the animal afterwards being kept alive 

 in a glass aquarium. 



" In about fifteen hours many of the ganglion cells and nerve- 



* Zool. Anzeiger, xv, (1892), pp. 375 — 377. 



