ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 603 



acetic acid was placed on the slide after fixation in osmic acid. This 

 tinges the nuclei of the Trypanosomes and does not affect their size. 

 The method of testing the effects of the technique was carried out as 

 follows : — The preparations were examined and drawn under exactly 

 similar conditions, i.e. the Microscope and drawing arrangements were 

 invariably the same ; the illumination was an end-on flame concentrated 

 by a collecting lens through a monochromatic screen on the mirror 

 of the Microscope, and thence reflected through a centring achromatic 

 condenser. 



The author then goes onto point out why he gave up slide-smears for 

 cover-glass preparations. The cover-slip is dropped down plump into 

 the fixative, and the films or smears were always stained and mounted 

 without being allowed to dry during any part of the process. The 

 use of cover-slip films necessitates a modification in the mode of applying 

 the osmic acid vapour. The requirements are a square block of hard 

 paraffin and a ground-glass ring ; the latter is heated and stuck on to one 

 surface of the block, and a hollow is then dug out in the block. Osmic 

 acid is placed in the cell thus made, and then the cover-glass with the 

 blood-smear placed thereon. After sufficient exposure, the cover-slip is 

 lifted off and dropped into alcohol, or some other fixative. 



The fixatives used were osmic acid vapour followed by alcohol, mix- 

 tures containing osmic acid, and mixtures in which corrosive sublimate 

 is the principal ingredient. The staining methods chiefly used were 

 Giemsa, Heidenhaiu's iron-hrematoxylin, and Twort's stain (a combina- 

 tion of neutral-red and light-green). 



For numerous other details the original should be consulted. 



Lendvai, J. — Ein neuer Apparat zur Fixierung und Farbung der in wasser 

 lebenden Mikrobien. Centralbl. Bakt., 2te Abt., xxiv. (1909) pp. 192-4 (2 tigs.). 



(3) Cutting', including- Imbedding and Microtomes. 



New Freezing and Cooling Arrangement for the Microtome.* 

 R. Krause, after discussing the advantages and disadvantages of several 

 cooling reagents, including liquid air, describes his experiences of solid 

 carbonic acid gas, which he has found very satisfactory. To obtain 

 carbonic acid in this condition the liquid form is allowed to issue slowly 

 from the steel cylinder in which it is bought, and as this issue is under 

 high pressure the sudden expansion lowers the temperature sufficiently to 

 cause a deposit of carl >onic acid snow. Small bags of the best silk velvet 

 were found to be the best receptacles for this solid, which was after- 

 wards transferred to a small Dewar flask, similar to those used for storage 

 of liquid air. Such a flask is of double-walled glass, the inside of the 

 walling being vacuous and silver plated ; the whole arrangement is 

 something like a beaker within a beaker (fig. 115), the two beakers being 

 united at their rims. This freezing-chamber is inclosed in a brass cylin- 

 drical case of suitable size for the microtome-stage, and lined with non- 

 conducting material (e.g. felt). The inner " beaker " receives a slightly 

 smaller brass cylinder, the upper side of whose bottom has a vertical 



* Zeitschr. wiss. Mikrosk., xxv. (1909) pp. 289-300 (4 figs.).,! 



2 Y 



