THE ROCKING MICROTOME. 453 



The advice of the makers as to use is that any thoroughly good 

 razor can be used, and the object to be cut should be embedded 

 in hard paraffin melting at about 55 C. The block containing 

 the object should then be fixed to the paraffin contained in the 

 object-holder of the microtome, by gently melting the surfaces. 

 The sides of the block must now be cut so that the opposite sides 

 are parallel ; it is then dipped into melted soft paraffin, that is, 

 paraffin with a low melting-point (about 48 C.), so that it is 

 coated all over, the object of which is to secure the cohesion of 

 the successive sections. The coating of soft paraffin is then re- 

 moved from two opposite sides, and if necessary the thickness is 

 reduced on the other two sides. Unless the sides are flat and the 

 coating of soft paraffin is very thin, the sections will not form a 

 good ribbon. The object-holder with the block attached is now 

 ready to be replaced on the microtome, care being taken that the 

 coated sides of the block are above and below, so that the one 

 coated side shall first come into contact with the edge of the razor. 

 The microtome will now cut sections adhering together and forming 

 a ribbon. The largest section which can be cut is 20 mm. in dia- 

 meter. 



In spite of its comparatively low price (5 complete), Galdwell's 

 Rocking Microtome makes beautiful series of sections. A disad- 

 vantage which it has in comparison with some microtomes is that, 

 inasmuch as the rocking arm moves through an arc, the section 

 cut is not a true plane but a portion of a cylindrical sheet, and 

 therefore is, even if only slightly, curved. For most small histo- 

 logical objects this, however, does not matter, and hence its wide 

 use in botanical laboratories. A German copy of it is made by 

 Jung of Heidelberg. 



Staining Microtome Sections. The staining method which has 

 hitherto proved best for the cell-contents of vegetable objects in 

 microtome sections adhering to an object-slide is Flemming's triple 

 staining with safranin-gentian-violet-orange, commonly known as 

 Flemming's orange method. Three colours come into use in it, 

 this being the greatest number which hitherto have, with any 

 advantage, been combined in the same object. These colours are 

 not mixed, but used consecutively, and each of them requires a 

 definite duration of action and suitable subsequent treatment. 

 Objects which have been fixed with Flemmiug's solution, or other 

 similar fluids containing chromic acid, always give very good results 

 with this staining, but with alcohol material, on the other hand, 



