152 SUMMARY OF CURRENT RESEARCHES RELATING TO 



imbedding mass. With a homogeneous paraffin it is surprising to see 

 with what wide latitudes as to melting-point the chains of sections will 

 come off. 



Schiefferdecker's Microtome for cutting under alcohol.* — Dr. P. 

 Schiefferdecker's improved microtome (fig. 34) is now provided with an 

 arrangement for cutting under spirit, as well as for raising the knife- 

 carrier and automatically raising tho preparation. There are, besides, 

 numerous practical improvements, but the principlo of the instrument 

 is unchanged. 



The angle of tho slideway and the weight of the slide itself are more 

 favourable. Any slipping of the band from the wheel is now prevented, 

 and the handle can be placed in any desired position. On drawing out 

 the slide, the band can be so fastened that it always remains in the proper 

 position. 



Bending of the metal parts owing to refractory preparations is 

 obviated, and the knife-guard is now so arranged that the pressure on 

 tho knife is as small as possible. In the illustration the arrangement 

 for raising the knife is not seen, as it is covered by the pan. In a very 

 simple way the knife-carrier is raised any required height merely by tho 

 crank action when the slide is drawn backwards. As the knife requires 

 to be raised a shorter distance for paraffin preparations than for unim- 

 bedded ones, the arrangement for raising it is so effected that this action 

 can be made at any desired position of the slideway. The position of 

 the preparation is automatically altered, also, in a very simple manner. 



A bar, which in its turn is moved by the crank, is set in motion by a 

 toothed wheel acting upon a micrometer screw. Upon this bar is fixed a 

 plate for regulating the amount or distance of raising. Expressed in 

 fractions these amounts are 0*005, 0*01, &c, to 0*05 mm. For most 

 cases these are sufficient, but if any other size be required the automatic 

 arrangement may be dispensed with, and the preparation raised by turn- 

 ing the milled head of the micrometer screw with the hand. Of course 

 any other denominator than 200 can be used for the fraction. For the 

 automatic motion of the micrometer screw a new striking mechanism has 

 been constructed, and this is found to be more effective than the catch 

 arrangement. 



The immersion apparatus is a flat quadrangular pan, in the bottom of 

 which, and just above the preparation-clamp, is a circular hole for the 

 preparation to pass through. The clamp, with the screws necessary for 

 the two turns, is placed within a cylinder, the upper edge of which, by 

 means of a short and wide caoutchouc tube, is united with a projecting 

 rim running round the hole in the bottom of the pan, so that, when the 

 spirit fills the pan and cylinder, the preparation always lies in the alcohol, 

 and yet can be pushed up and down with the cylinder without difficulty. 

 The screws which alter the clamp are turned with keys. The knife, 

 which has a straight handle, is fastened by means of two screws to a 

 thick metal-piece (the connecting-piece), Jind this in its turn is united by 

 screws with the plate of the knife-carrier. The connecting-piece, to the 

 under surface of which the knife is fastened, passes over the pan in such 

 a way that it projects into the spirit. 



Underbill, H. M. J. — Section-cutting applied to Insects. 



Sci.-Gossi}-), 1838, pp. 1-4. 



* Zeitschr. f. Wiss. Mikr., iv. (1887) pp. 340-3 (1 fig.). 



