324 



SUMMARY OF CURRENT RESEARCHES RELATING TO 



similar minute bodies are so massed together that one lies iK'hiud 

 another and is thus liable to be missed in counting, the compressorium 

 described below may prove useful in overcoming the difficulty, which 

 none of the ordinary compressoria will do. 



AVhen such a mass of chromosomes is flattened out by pressure, the 

 individual chromosomes behave somewhat as would the seeds of a pulpy 

 fruit under similar circumstances. They appear to be of a different 

 consistency from the material in which they lie, and behave under 

 pressure as if harder and more compact than the surrounding matter. 

 Under moderate pressure they do not show much tendency to break in 

 pieces, but rather to accommodate themselves to the narrower quarters 

 by rearranging themselves more nearly in one plane. So far as enumera- 

 tion of the chromosomes is concerned, this new arrangement has two 

 advantages : 1st, they may all be more readily brought into a single 



Fig. 4. — Two curved, perfor- 

 ated, steel springs made from 

 thin, safety-razor blades, as de- 

 scribed in the text. These two 

 forms, while of the same length, 

 nearly 1 in., are of different 

 degrees of springiness ; that at 

 the left beinsr the weaker. 



Fig. 5. — Portion of a 3 by 1 in. glass 

 microscope slide enwrapped with thin metal 

 as described in the text, a, thin metal 

 wrapper ; h, one of the springs phown in 

 fig. 4, placed in position on the slide so as 

 to press the small round cover-glass, c, against 

 the slide, e\ d, aperture in the back of the 

 metal wrapper, a. The ends of the spring, b, 

 enter through the notches on the edges of the 

 wrapper, a, so that in being applied the spring 

 does not need to be rotated more than a few 

 degrees. 



view, that is, all brought into focus at one time ; 2nd, in the flattening- 

 out process, they slip one over another somewhat, and recede from each 

 other — for instance, as the seeds inside a grape will do, when similarly 

 pressed. 



The compressorium I have devised to secure this effect is constructed 

 as follows : Take a safety-razor blade — one of the thinnest kind, liaving 

 perforations an eighth of an inch in diameter — and soften it by heating 

 it to a red heat. With shears, cut a somewhat diamond-shaped piece 

 from the softened blade, so that tbe " diamond " is about three to four 

 times as long as wide, and has one of the round apertures in its centre ; 

 bend this elongated " diamond " into a symmetrical bow whose depth is 

 •| in. or more. (See fig. 4.) Heat the bow in a flame to a cherry-red 

 and plunge it into cold oil or water to harden it. This will result in a 

 springy piece of metal that can be utilized to exert pressure on a small 

 cover-glass under which are mounted cells containing the chromosomes 



