666 SUMMARY OF CURRENT RESEARCHES RELATING TO 



adjustment of section-thickness from 5 to 30 mikrons ; maximum 

 section-plane 30 x 25 mm. ; maximum block-height 20 mm. ; inclina- 

 tion of knife to section-plane regulated by clamping-screws ; displace- 

 ment of knife or object impossible ; applicability for freezing 

 (ethyl chloride) ; easy working by means of a well-balanced flywheel 

 gear ; compactness for travelling. No pains have been spared to 

 secure precision of movement, and the machine may be operated 

 quickly or slowly. The large clamp T fastens the instrument rigidly 

 to the working table. The two strong pillars of the knife-holder X 

 are cast on to the ground-plate, and the groovings for the knife are 

 fitted with clamps for regulating the knife-inclination in order to adapt 

 it as delicately as possible to the requirement of the object. The 

 crank of the vertical slide V is balanced by the flywheel, and is operated 

 in a very simple manner by the gearing ; it can also be fixed in its 

 highest position by a stop, so that coarse adjustments, supplementary 

 paring of the block, treatment of the freezing chamber with ethyl 

 chloride, etc., may be undertaken. The object-slide M is adapted on its 

 upper half to excentric movement, and is actuated by a micrometer- 

 screw of 0"5 mm. thread, and the progress forward of the preparation 

 always follows upon the knife-cut. The ratchet 11 engages in the 

 teeth of the cogged wheel R connected with the micrometer-screw and 

 rotates it 1 to 6 teeth at each drop of the vertical slide according to 

 the adjustment of the screw-head E ; each tooth = 5 mikrons. The 

 screw-head E is graduated into 1 to 6 parts, which correspond to the 

 number of teeth to be moved. In addition to these automatic section 

 arrangements it is possible, by putting the ratchet II out of gear, to 

 cut freehand sections less than 2\ or greater than 30 mikrons, as 

 desired. A well-defined straight line with millimetre divisions is used 

 for the adjustment of blocks with parallel edges, and is inserted in the 

 knife-holders conformably with the adjustment of the object in the 

 object-holder. When the flywheel is rotated the block is lowered (or 

 raised) just sufficiently to allow the upper (or lower) surface to come to 

 the right level for cutting ; a needle then traces a furrow in the block, 

 which can then be trimmed off. 



(4) Staining' and Injecting. 



Differential Staining of Spores.* — G. Proca and P. Danila find that 

 the easiest way of staining killed spores is to treat the film with boiling 

 decinormal solution of caustic soda for a few minutes and then to stain 

 with their methylen-blue-fuchsin solution. 



Twort's Neutral-red and Light-green Stain.j — This reagent is 

 prepared by making up half-saturated solutions of neutral-red and of 

 Grubler's Licht-griin in distilled water. The neutral-red solution is 

 placed ina large open vessel, and sufficient light-green solution is added. 

 A precipitate forms, and this is allowed to sediment. The supernatant 

 fluid is decanted off, and then the precipitate is rinsed in distilled water 



* C.R. Soc. Biol. Paris, lxvii. (1909) pp. 307-9. 



t Quart. Journ. Micr. Sci., liii. (1909) pp. 755-808 (3 pis.). 



