ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 



133: 



end of a wide cone of light was used. The light, before entering the con- 

 denser system, was passed through a Gifford's screen, and in this way the 

 image was much improved. '1 his screen is made by dissolving methyl- 

 green in hot glycerin, placing the solution in a glass tank, and immersing 

 in the liquid a piece of Chance's signal-green glass. If constructed with 

 care the red end of the spectrum may be cut off to the line F. Another 

 use of this screen is that even unstained organisms may be examined, 

 and with comparatively wide illuminating cones. 



Neisser's Stain for the Diphtheria Bacillus.* — Dr. R. T. Hewlett 

 describes Neisser's diagnostic stain for the diphtheria bacillus. (1) One 

 gram of methylen-blue (Griibler) is dissolved in 20 ccm. of alcohol 

 (96 per cent.), and mixed with 950 ccm. of 

 distilled water and 50 ccm. of glacial acetic Fig. 33. 



acid. (2) Two grams of vesuvin are dis- 

 solved in 1000 ccm. of boiling distilled 

 water, and the solution cooled and filtered. 

 Cover-glass preparations are stained in 

 (l)for 1—3 seconds, rinsed in water, counter- 

 stained in (2) for 3-5 seconds, washed in 

 water, dried, and mounted in balsam. The 

 bacillus appears as a slender longish rod 

 stained brown, and generally containing 

 granules of a deep blue or inky tint. There 

 are usually two granules, one at each pole, 

 and occasionally a third in the middle. 



Histological Fixation by Injection.! — 

 Mr. F. M. McFarland describes a simple 

 apparatus for injecting small animals with 

 a fixative solution. The apparatus (fig. 33) 

 consists of two glass funnels connected with 

 the arms of a Y-tube by rubber tubing. 

 The leg of the Y-tube connects, also by 

 means of rubber tubing, with a cannula 

 which, of course, may be of any size. The 

 main tube A has a lateral tube C for removal 

 of air-bubbles. All the rubber tubes are 

 supplied with pinch-cocks. The tube B is 

 filled with normal saline solution warmed 

 to body temperature, and to it are added a 

 few drops of lactic acid or amyl nitrite to 

 ensure dilatation of the blood-vessels. The 

 tube A is filled with warm fixative solution, 

 e.g. Zenker's. The cannula having been in- 

 troduced into the aorta, say, of a kitten, the 

 vascular system is first flushed with the 

 saline solution, and when the blood has been removed the fixative in 

 A is run through. The pressure, of course, will vary according to the 

 height the funnels are raised. 



* Trans. Jenner (late British) Inst. Pivv. Med., ser. i ; . (1893) pp. 201-6. 

 t Journ. App. Micr., ii. (1S99) pp. 541-2 (1 fig.). 



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