228 



SCIENCE-GOSSIP. 



might easily be overlooked, and it seems to me that 

 there may be something in this fact more than mere 

 coincidence. These sheaths or cases fall off the 

 buds in spring, and throughout the summer thickly 

 strew the ground below the trees where the 

 Clausilise live among the dead leaves." In the 



discussion which followed, it transpired that Mr. 

 Christy remembered having found the shells of 

 one species in the gizzard of a blackbird, which 

 goes some way to prove the need of protective 

 resemblance by Clausilias. 



" Holmesdale," Brentwood, Essex. 



AN IMPROVED MICROTOME. 



("*■ REAT advances in recent years have been 

 ^-* made in microtomes ; it is not so many years 

 ago that the internal structure of any soft animal 

 tissue could only be examined by cutting sections 

 by hand with a razor and mounting each section 

 separately before examining it under a microscope. 

 Skill was required in cutting these sections, and it 

 was a slow process even with the most dextrous 

 person. The sections were thick, no two sections 

 were of the same thickness, and no section was of 



most simple : the object is embedded in a block of 

 melted paraffin, and when set, the edges are 

 cut so that the object is in the centre of a 

 rectangular block. The outside of this block is 

 then coated with some soft paraffin ; the effect 

 of this is, that when the sections are cut they stick 

 together at their edges and form a ribbon. The 

 ribbon can then be mounted in strips on the glass 

 side ready for the microscope. When we consider 

 the thinness of the sections and that they are only 



ROCKING MICROTOME, NEW PATTERN TO CUT FLAT SECTIONS. 



uniform thickness throughout. Some extremely 

 good work was no doubt done in this way, and 

 much new knowledge was obtained of the internal 

 structure of small bodies. Early section-cutters 

 were a great advance on hand work, the sections 

 were far thinner and were of uniform and equal 

 thickness, but each section had to be removed and 

 mounted separately. In the latter forms, however, 

 the " ribbon method," introduced by Mr. Caldwell, 

 is used, and the time previously spent in the 

 individual cutting and manipulation of each section 

 has been saved. This point is in itself of great 

 importance, but it is of no less importance that it is 

 now easy to arrange hundreds of sections on one 

 glass slide in rows, in the order in which they are 

 cut. A whole series of sections are thus studied by 

 merely moving the glass slide along and examining 

 each consecutive section as it comes into the field 

 of view of the microscope. The ribbon method is 



held together by the soft paraffin at their edges, 

 the strength of the ribbon as well as the ease with 

 which it can be manipulated, is most remarkable. 

 It is not difficult to cut sections -oooi inches thick 

 with the modern microtome, and we will give an 

 example to illustrate what this means. Suppose 

 we take an ordinary paraffin candle and cut it up 

 into sections of this thickness. We will suppose 

 the candle to be 10 inches long and g of an inch in 

 diameter, this being the size of an ordinary candle. 

 This would then cut 100,000 sections ; if these 

 sections were placed in a row touching each other, 

 the row would be just over x\ miles long. 



The original rocking microtome was first brought 

 out by the Cambridge Scientific Instrument Com- 

 pany, in 1885, and was one of the earliest section 

 cutters using the ribbon method. It differed 

 entirely in design from all other section cutters 

 which had been made up to that date ; it is, 



