WITH THE MICROSCOPE. 45 



77. noubie-biartert or v iifiitin's Knife. This instrument is of 

 the greatest value in making thin sections of soft tissues, but care is 

 required to keep it in good order. It is soon made blunt if used for 

 cutting fibrous or cartilaginous textures. By its aid very beautiful 

 sections of the kidney, liver, and other soft glandular organs may be 

 obtained with the greatest facility. The blades should always be 

 dipped in water or glycerine just before use, for, if wet, the operation 

 of cutting is much facilitated, and the section more easily removed 

 from between the blades. Immediately after use the blades should 

 be washed in water, and dried with a soft cloth, or piece of wash 

 leather. If a drop of water gets into the upper part of the knife 

 where the blades meet, the screw must be taken out, and each blade 

 cleaned separately. With care in cleaning it, the knife may be kept 

 in use a long time. 



There are two forms of Valentin's knife ; in one the blades are 

 sharp on both edges and of a lancet-shape, and in the other, which I 

 much prefer, they are sharp at the point and wide at the base, so that 

 the cutting edge slants downwards from the point, and they only cut on 

 one side, pi. XV, fig. 79. The best form of Valentin's knife that I 

 have used is that which has lately been made by Mr. Matthews, fig. 78. 

 The blades of this knife can be completely separated from each other 

 and easily cleaned. The distance between the blades is regulated by 

 a little screw, which is a most convenient arrangement. This knife 

 has been further improved by Mr. Matthews, by the addition of two 

 screws, so that the perfect parallelism of the two blades is ensured. 



78. Razor. A strong knife made like a razor is very valuable 

 for making sections of many tissues, pi. XV, fig. 81. 



79. scissars are useful instruments for cutting small thin sections 

 of different tissues. The most convenient form for this purpose is 

 one in which the blades are curved as in pi. XV, fig. 83. When only 

 very small portions of a tissue are required for examination, they will 

 be more readily removed with the scissars than with any other instru- 

 ment. Several pairs of scissars are required for microscopical pur- 

 poses. Besides the ordinary form used for dissection, a small pair, 

 with curved blades, a pair of very delicate scissars with blunt points, 

 fig. 82, such as are employed for the dissection of insects, will be 

 found of use. Some time since, I devised a new form of spring 

 scissars, somewhat resembling the microtome. These are particularly 

 well adapted for dissecting the nervous systems of insects, for follow- 

 ing out the delicate ramifications of nerves and other minute dissec- 

 tions, pi. XV, fig. 84. 



so. Needles of various sizes are very useful instruments to the 

 microscopist. They are employed for making minute dissections ; for 



