600 SUMMARY OF CURRENT RESEARCHES RELATING TO 



on three accurately worked projecting guides, is also heavy, and is tho- 

 roughly secured by means of a clamp ; a slip of the knife in the cutting 

 of hard objects is impossible. 



The object-slide, 7*5 cm. long, is solidly built, and moves on an in- 

 clined plane only 12 "5 cm. long, which makes an angle of 15° with tbe 

 horizon. It moves with perfect safety and rigidity between two metal 

 guides, and on account of the inclination of its path, the horizontal 

 projection of its movement is proportionately slow. 



The object-holder is easily adjustable in the three directions of space, 

 in the vertical by rack-and-pinion, and can, by the simple action of a 

 screw d, be set higher or lower, or even removed altogether. 



The micrometer sci ew is fixed, that is, it is never necessary to remove 

 it from the mother screw. The fine adjustment is by a micrometer 

 screw of the construction usual with microtomes ; a circular sheath with 

 accurately divided toothed periphery enveloping the screw. A circular 

 segment h, graduated in degrees, can be pushed into position, and adjusted 

 so that the number of teeth (1 tooth = 1 p) can be set. By moving the 

 handle h, the irpper end of the circular segment strikes against a metal 

 cross-piece, which serves as a stop, and thus rotates the toothed wheel, 

 and moves on the micrometer-screw so that uniformly thick sections are 

 automatically obtained. When the micrometer-screw is quite run out, 

 it can, in a circular notch of the vertical guide of the microtome, be 

 rotated through 180°, and then commence again, the other end of the 

 micrometer-screw being now in contact with the object-slide. Thus the 

 result is an uninterrupted working of this screw. In order to acquire 

 contact with the micrometer-screw in-this new position, the object-slide 

 must be pushed back about 25 mm. The corresponding slight difference 

 (about 7 mm.) of height between knife-edge and cutting plane of the 

 preparation can now be easily set right by means of the pinion Tr. 



The arrangement is especially useful in serial-section making. 



(4) Staining' and Injecting-. 



New Reaction for Woody Tissue. * — C. Maule has found that 

 woody tissue, treated with permanganate of potash, followed by hydro- 

 chloric acid and ammonia, turns red. 1 grm. of permanganate is dis- 

 solved in 100 ccm. water, and the sections are immersed for 5 minutes. 

 They are then decolorised in HC1 for 2 or 3 minutes. After the addi- 

 tion of ammonia, or holding them over a bottle containing ammonia, 

 they turn red. The reaction may be hastened by heating the perman- 

 ganate on the slide, and instead of ammonia caustic potash or soda may 

 be used. The time the permanganate takes to act varies with different 

 plants, the Coniferae being especially resistant. 



Researches with Neutral Red.f — Prof. S. Mayer reports on some 

 researches made with neutral red, a pigment which in many cases will 

 impart an intra vitam staining to cell-granules. According to Mayer, 

 the pigment is not poisonous, and is possessed of great staining power. 

 Frog and salamander larvae were immersed in dilute solutions, and soon 



* Fiinfstiick's Beitr. z. wiss. Bot., iv. (1900) pp. 176-85. See Zeitschr. wiss. 

 Mikr., xviii. (1901) pp. 108-10. 



t SB. Prager Vereins " Lotos." See Zeitschr. wiss. Mikr., vii. (1901) pp. 20-1. 



