88 



Journal of Applied Microscopy. 



The Cutting of Paraffin Sections in 

 Ribbons. — If the tissues are well imbed- 

 ded and not too hard, and if the knife 

 is sharp and properly adjusted, paraffin 

 sections may be cut in such a way that 

 each succeeding section adheres to the 

 preceding one, so that actual ribbons of 

 paraffin sections may be made. In order 

 to do this, the knife should be at right 

 angles to the microtome. The paraffin 

 block should be trimmed in such a way 

 that when clamped in the microtome 

 ready for cutting sections, the surface 

 of the paraffin block facing the knife 

 should be exactly parallel to its edge, 

 also the opposite side of the block. In 

 other words, two sides of the paraffin 

 block should be parallel to each other 

 and to the knife, then if the paraffin is 

 of the right consistency, which must be 

 ascertained by trying, the sections as 

 they are cut will adhere to each other 

 and form a ribbon. If the sections do 

 not adhere to each other, it is quite 

 probable that the paraffin is a little too 

 hard. This may often be remedied by 

 holding an old knife or other metallic 

 instrument which has been heated in a 

 flame, near the two parallel surfaces. 

 Care should be taken not to allow this 

 instrument to touch the paraffin. This 

 is a very convenient and rapid way of 

 cutting paraffin sections. 



The Cutting of Celloidin Sections. — 

 For cutting sections of tissues embed- 

 ded in celloidin, it is necessary to clamp 

 the knife at an angle of about 30° to the 

 microtome. In a former article I have 

 explained the fixing of the celloidin 

 block to a small wooden block. Before 

 fastening the block in the clamp on the 

 microtome, the celloidin should be 

 trimmed with a sharp knife from the 

 top of the block until the tissue is 

 exposed, care being taken to leave a 

 flat surface. The sides of the celloidin 

 block are then trimmed down, if neces- 

 sary, to within about one-sixteenth of 

 an inch of the tissue. The block is now 

 clamped in the microtome, at such a 

 level that it just escapes the knife when 

 drawn over it. During the process of 

 cutting, the knife, as also the tissue, 

 must be kept constantly inoistened with 

 80% alcohol. This is perhaps most 

 easily accomplished by taking up the 

 80% alcohol with a rather large camel's- 

 hair brush and dipping this on the cel- 

 loidin block and on the knife. 



A number of rather thick sections are 

 cut, until the knife touches the entire 

 surface of the block or until the tissue 

 is well exposed. The sections may now 

 be saved. The block is raised twenty 

 to fifteen microms, four to three turns 

 of the milled head from left to right, 

 and the knife, which should be well 



moistened with 80% alcohol, is drawn 

 over the block with a steady pull, not 

 with a jerk. The sections are trans- 

 ferred from the knife to distilled water. 

 This is perhaps most conveniently done 

 by placing the ball of one of the fingers 

 of the left hand under the edge of the 

 knife, in front of the section, and draw- 

 ing the section down on to the finger 

 with the camel's-hair brush. The finger 

 is then dipped into the distilled water, 

 when the section floats off.^ If the sec- 

 tions cannot be stained within a few 

 hours after they are cut, they are best 

 transferred to a dish containing 80% 

 alcohol, in which they may be left until 

 it is desired to stain them. 



( To he Continued. ) 



An Improved Form of Paraffin 

 Embedding Table. 



In previous numbers of the Journal 

 several persons have noted and com- 

 mended a simple form of paraffin embed- 

 ding table. Such a table is useful in 

 many ways besides in embedding, and 

 is certainly the simplest as well as in 

 some respects the most satisfactory con- 

 stant-temperature apparatus for all 

 laboratories where gas is not accessible. 

 It is my purpose to call attention here 

 to a slightly modified form which has 

 proved itself superior to the older type- 

 in several respacts. The general form 

 which is represented in the figure may be 

 described as that of a goose-neck table; 

 it has reached the form at present in 

 use in this laboratory by minor changes 

 at the hands of a number of persons, so 

 that I can claim no peculiar originality 

 in its construction. 



The table is made of a triangle of sheet 

 copper with a base of six inches and 

 perpendicular height of fourteen inches. 

 The edges of the triangle are turned 

 under and inward, giving to the table a 

 smoothly rounded margin. In height the 

 main part of the table measures two 

 inches, and it is about four inches high 

 under the apex of the triangle, where is 

 placed the heating flame, which may be 

 gas or an oil or alcohol lamp; with any 

 of these, provided the position of the 

 table is sheltered from sudden changes 

 due to draughts, a uniform temperature 



