ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 711 



excellent substratum for the bacillus of soft chancre, of syphilis, aud 

 other infective diseases of man and animals. The insects employed 

 have been Orthopfcera, Rhynchota, Hemiptera, Coleoptera, Lepidoptera, 

 Diptera, Kymenoptera. The insects lived on the average for about 

 2 weeks. Inoculations were effected with a fine sharp sterilised needle 

 in the heart, tracheal apertures, in the fat-bodies, between two thoracic 

 segments as far from the digestive and reproductive organs as possible. 

 The insects must be kept, especially in summer-time, in a moist atmo- 

 sphere. Cultivated in insects the bacillus of soft chancre becomes 

 shorter, gradually being transformed into cocci. It is also more diffi- 

 cult to stain than when obtained directly from a bubo. Although suc- 

 cessful cultivations of syphilis were obtained, the results are not yet 

 published. 



(2) Preparing Objects. 



Rapid Method for Making Slides of Amoebae. * — M. A. Willcox 

 removes amoebae from detritus by means of a thin-walled dipper under 

 a magnification of some 20 diameters. The amoeba is then dropped on 

 a slip, and, the excess of water having been removed, the animal is 

 fixed with a drop of picric-alcohol (saturated solution of picric acid in 

 50 p.c. alcohol), after which it is dehydrated with alcohols of increasing 

 strength. This done, the amoeba is fixed to the slip with a droplet of 

 very dilute collodion, after which the preparation is hardened in 80 p.c. 

 alcohol. It may then be stained with borax-carmine, hematoxylin, &c. 

 Amylic alcohol should be used for dehydration. If the specimen be 

 large, supports may be necessary. Mount in balsam. 



Preparation of Crystals as Microscopic Objects.f — S. E. Dowdy 

 gives three principal methods for making preparations of crystals. The 

 first consists of evaporating down a saturated solution of the salt until 

 enough moisture has been driven off to enable the crystals to form 

 rapidly on cooling. Make a saturated solution of the salt in distilled 

 wator, and deposit a drop with a pipette in the centre of a slide. Slope 

 the slide to make a film, and remove superfluous fluid with blotting- 

 paper. Hold the slide over a flame until a thin film of salt forms at the 

 edges, then withdraw and allow to cool, and examine under Microscope. 

 If satisfactory, mount in balsam. If the salt be insoluble in water, 

 other suitable solvents are used. These evaporate without the aid of 

 heat. Crystals formed from such solutions will probably require a dif- 

 ferent mounting medium, such as castor oil, or one in which they are 

 not soluble. Another method is to dissolve gelatin or gum acacia in 

 distilled water, and to add to this a few drops of a saturated aqueous 

 solution of the salt. A drop of the warm mixture is then deposited on 

 a slide, the superfluous fluid drained off, and the slide put aside to cool. 

 Any salt soluble in water is suitable for this procedure. 



The second principal method is by fusion. Place a small quantity, 

 say of salicin, on the centre of a slide, and heat over the flame until it 

 just fuses, withdraw before it chars, and allow it to cool gradually, and 

 if successful mount in balsam. Crystals of fatty substances, such as 

 spermaceti, paraffin, &c, are preparable in a similar way. When melted 



* Journ. Applied Microscopy, iv. (19ul) p. 1450. 

 t Pharm. Journ., lxvi. (1901) p. 198. 



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