514 SUMMARY OF CURRENT RESEARCHES RELATING TO 



A further inconvenience, namely the too complicated arrangement for 

 altering the horizontal position of the carrier, has been obviated. 



The knife-handle now, instead of being flat, is made round so that it 

 can be fixed in any position quite easily by means of the screw F (fig. 93). 

 The handle passes througb an iron block d, and is tigbtcned up by 

 means of the winged screws. The exact shape of the knife fitted with 

 a handle for sharpening is shown in fig. 94. For cutting hard objects 

 such as dense wood and bark, the author advises the knife to be ground 

 like a plane. 



After alluding to the advantage of using Jung's section-stretcher in 

 connection with bis microtome, the author passes on to the treatment of 

 vegetable preparations. In a former communication the author advised 

 the imbedding of roots, barks, and wood in glycerin jelly. But as the 

 vacuum apparatus necessary for this procedure is not always available, 

 he now occasionally resorts to the older methods of softening the pre- 

 parations in spirit, glycerin, and water, and this is specially adapted to 

 hard close-grained objects. Woods are always placed in glycerin and 

 water, and can then be cut with an unwetted knife without tearing. If 

 afterwards the sections are placed in glycerin to which some caustic 

 soda has been added they are easily unrolled. 



With regard to fruit and seeds of a hard consistence and structure, 

 such as Strychnos potatorum, S. nux vomica, Coffea arabica, and the 

 kernel of Phoenix dactyl if era, preparations easy to be cut can be obtained 

 in two or three days by softening the objects in dilute caustic soda or 

 potash. But as any further microchemical examination is useless owing 

 to the destruction of the alkaloids by the caustic alkalies it is preferable 

 to soften the seeds by means of steam. This is done in a wide funnel into 

 which a piece of wire gauze is placed as a sort of filter, and upon this 

 the seeds. The funnel should be lined with filter paper to carry off the 

 condensation water, and the funnel supported on a tripod in a water- 

 bath. In 30 to 60 minutes the objects will be found sufficiently softened 

 to cut quite regular sections from. 



Some objects, such as almonds and cocoa-beans, crumble away under 

 the action of the knife, and therefore require to be imbedded as they 

 cannot be fixed directly in the jaws of the object-carrier. Glycerin 

 gelatin is unsuitable for this purpose as the mass does not offer sufficient 

 resistance, and although paraffin is usually unsuitable owing to its com- 

 plicated manipulation it gives fair results by the following procedure. 

 The seeds should be slightly warmed in order to drive off as much 

 moisture as possible, and quickly immersed in paraffin only heated a few 

 degrees above its setting point. They are then left to cool until a thick 

 coating has developed upon them. In this way the paraffin will be found 

 to have filled up all the chinks and crannies in the seeds, and not only offer 

 sufficient resistance to the knife, but will also invest the sections with a 

 sheath sufficiently strong to prevent their crumbling away. The paraffin 

 is then dissolved out with benzin, ether, or chloroform, and the prepara- 

 tions mounted in glycerin jelly or in Canada balsam according to the 

 special idiosyncrasies of the seeds. 



Small seeds and fruits, such as those of the Solanaceae and Umbelli- 

 ferse, should be imbedded in a paraffin of a high melting-point. Glycerin 

 jelly, to which a little sublimate is added, is recommended for mounting 

 permanently. Air-bubbles are easily got rid off by slightly warming 

 the slide and then pressing on the cover-glass with a lead roller, 3 cm 



