ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 235 



end of the spectrum give the worst results. Golgi preparations give 

 most satisfactory negatives. Sections stained with liEernatoxylin or 

 other blue dyes are very actinic, and it is necessary to exaggerate the 

 shadow thrown by them. This is done by colouring the light before it 

 enters the condenser of the Microscope, with a light filter or colour 

 screen of a tint complementary to the stain. In most cases the screen 

 sold by photographic dealers for landscape photography will be found 

 sufficient ; this is a light brown-yellow glass screen. Should the section 

 be thin and the staining slight or faded, greater depth of colour will be 

 necessary in the light-filter. This can be obtained by staining a film 

 of gelatin on a glass plate with picric acid, or, better still, by using a 

 glass trough or bottle filled with a solution of bichromate of potassium. 

 The light-filter, however constructed, must be placed between the light 

 and the Microscope. If a coloured glass screen, it is fitted into a frame 

 which is hinged to the platform on which the Microscope stands, so 

 that it can be raised or lowered at discretion. To this frame is also 

 hinged a sheet of vulcanite, in order to cut off all light from the 

 Microscope when manipulating the dark slide before and after making 

 an exposure. 



If possible, all preparations of a series to be photographed should 

 be stained with the same dye, as this will simplify the calculations 

 necessary to find the time of exposure, will suit one quality of plate 

 and one light-filter, and will render possible an exact comparison of the 

 various results and a correct relation of their several details. 



Method of Demonstrating the Secretory Canaliculi in Supra- 

 renal Capsules.* — C. Ciaccio fixed the fresh tissue for 15 to 20 days in 

 Miiller's fluid and then transferred the pieces to a 1 p.c. solution of 

 nitrate of silver for 24 hours. Better results were obtained by fixing 

 in the following mixture : — Formalin 15 c.cm. ; bichromate of potassium 

 5 grm. ; distilled water 100 c.cm. Good preparations may be obtained 

 by cutting sections with a razor from the pieces directly removed from 

 the silver nitrate, but paraffin sections were necessary for demonstrating 

 the more delicate details. The sections were stained with acid fuchsin, 

 by Zimmermann's silver chloride method, and in other ways. The animals 

 used were guinea-pigs, rabbits, and cats. By this procedure pericellular 

 canals having intracellular ramifications were demonstrated. 



Staining Diphtheria Bacilli and Cholera Vibrios. f— W. G. 

 Schauffler, in a preliminary communication, states that by means of 

 Loeffler's methylen-blue, pyronin, and hydrochloric acid-alcohol, diph- 

 theria bacilli from fresh membrane, or from cultures, stain easily and 

 without the aid of heat. The poles appear red, while the rest of the 

 cell-body is stained blue. Pure cultures of different races of cholera 

 vibrios show on staining with methylen-blue, decolorising with hydro- 

 chloric acid-alcohol and contrast-staining with dilute pyronin, dark 

 granules in the bluish-red bodies. 



New Method of Staining Flagella.j — E. Gemelli describes the 

 following method for staining flagella. The cover-glasses are boiled in 



* Anat, Anzeig., xxii. (1903) pp . 403-7 (3 fiV s .). 



t Allg. Med. Central-Ztg., 1902, p. 827. See Centralbl. Bnkt., 1" Abt. Kef., 

 xxxii. (1903) p. (J87. J Centralbl. Bakt., 1" Abt. Orig., xxxiii. (1903) pp. 316-9. 



