CHAPTER XI 

 SPECIAL METHODS 



While the methods already described are sufficient for most of 

 the routine work of the ordinary laboratory, special methods are 

 often necessary for special cases. In nearly every piece of research 

 work the investigator will find some modification necessary before 

 he can secure the best results. A few methods designed to meet 

 special difficulties are given in this chapter. 



VERY LARGE SECTIONS 



It is sometimes desirable to cut very large sections. Sections 

 as large as a cornstalk may be cut freehand or in celloidin. A section 

 of a stem of Zamia 5 or 6 cm. in diameter is difficult to handle by the 

 usual methods. If a large microtome, such as is used in cutting 

 complete sections of large brains, is available, the piece of stem is 

 easily held for the cutting. Some of the medium-sized sliding 

 microtomes now have a rigid clamp which will grip a block 3 cm. 

 square. The lower part of the piece can then be trimmed to fit the 

 clamp, leaving the upper part round, so that sections across a stem 

 6 or 7 cm. in diameter may be cut without much difficulty. With a 

 rather soft stem, like Zamia', the surface must be flooded with 95 per 

 cent alcohol after each section, if it is desirable to cut thin sections. 

 From stems 3 cm. in diameter, sections can be cut at about 20 to 

 30 fj,. If the section is not more than 3 or 4 cm. in diameter, it can 

 be mounted on a 50X75 mm. slide. Sections 6 or 7 cm. in diameter 

 can be mounted on lantern slides; if large covers are not available, 

 use another lantern slide for a cover. It will be easier to get neat 

 mounts if the cover is cut down so as to leave a margin 2 or 3 mm. 

 wide. It is not easy to mount a thick section between two lantern 

 slides of the same size, on account of the balsam which oozes out at 

 the edges. Such preparations may be used directly as lantern slides. 

 Large sections of the stem of a tree fern make good mounts without 



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