32 THE METHOD OF SECTION-CUTTING WITH IMPROVEMENTS, 



When this has been done the top of the paraffin-stick containing 

 the specimen is dipped into a freezing molten mass of soft paraffin 

 and instantly withdrawn. 



The desired coating of soft paraffin will then be found on the 

 outer surface. 



There should always be continuous series of sections cut and 

 mounted, one after the other. For certain things, and particularly 

 for a preliminary investigation, this is not necessary to such an 

 extent, and it will save time, trouble and material, if in such a case 

 every second section is cut thick and thrown away, and every 

 second cut to the required fineness and mounted. 



The thickness of sections is a point on which a great deal 

 depends. The mutual position of whole organs or groups of cells 

 can generally be ascertained much better by means of thick 

 sections and low powers, than by means of the very fine sections. 



For histological detail a section is rarely too fine. The thick- 

 ness required varies with every case, and the thickness to choose 

 must be left to the investigator and his experience. 



For an investigation into the structure of a rare and valuable 

 specimen, a continuous series of sections might perhaps be recom- 

 mended, which are alternately very thin— as thin as they can be 

 made — and of medium thickness, perhaps 0'005 — 0'02 mm. 



Mounting. 



The sections when attached to one another as a ribbon, can be 

 placed on a slide by cutting a portion of the ribbon corresponding 

 in length to the size of the slide off, and placing it there. Other 

 wise it is necessary to place the sections as they are made, one after 

 the other on the slide. It is hereby very important, that they all 

 should be parallel to one another. 



Before placing them on the slide, the latter must receive a 

 coating of shellac. White shellac is dissolved in absolute alcohol 

 and allowed to stand. A sediment will form and the clear solution 

 can be poured off. This is put on to the slide with a brush just 

 before use. 



