ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 
535 
position, in tlie following manner : — A cell of the requisite dimensions 
is constructed and small drops, close together in rows, of thick collodion 
and clove oil, are placed therein. An egg of Limulus or head of insect 
embryo, &c., is taken out of the clove oil, drained and placed in a drop 
of collodion in any desired position. A great many eggs may thus be 
arranged like serial sections under one cover-glass. Before adding the 
balsam the slide is immersed in turpentine, which serves to wash away 
the clove oil, and leave the eggs firmly fixed in the collodion. The 
only precaution necessary is not to use too much collodion. It is sur- 
prising to find the small amount necessary, and the firmness with which 
the objects are held in place by it. 
Cleaning Dirty Slides and Cover-glasses.* — Prof. Zettnow finds 
that the following fluid is very useful for cleaning slides or covers dirty 
with oil or balsam. Two litres of the fluid, which may be used five 
or six times, will clean 150-200 slides and about 300 cover-slips: — 
200 grm. of red chromate of potash are dissolved in 2 litres of hot 
water, and then 200 ccm. of strong sulphuric acid are gradually added, 
the mixture being stirred constantly the while. 
It is necessary, of course, to previously remove the covers from the 
slides. This is easily done by heating them for two or three seconds 
over a Bunsen’s burner, when the two can be easily separated. Slides 
when soaked in this fluid are easily cleaned, as the fluid softens the 
resin, and after an immersion in spirit they are brightened up with a 
cloth. 
Cover-glasses should be placed in a porcelain vessel filled with the 
fluid and this heated in a water-bath for 10 minutes. The softened 
resin floats up as a greenish scum, and this can be easily removed from 
the surface. When all the covers seem clean they are to be washed with 
water, and afterwards immersed in a dilute caustic soda solution. This 
should be warmed again in a water-bath for about 5 minutes. The last 
two stages are repeated, after which the covers are placed in spirit for 
a while, and then dried with a clean cloth. 
(6) Miscellaneous. 
Diagnosis of Cholera by the Microscope.f — M. J. Denys states 
that it is almost always possible to make a diagnosis of cholera by 
means of a microscopical examination of the vomit or dejecta, the basis 
of the diagnosis being founded on the mobility of the organisms, which 
is much greater in these fluids than in cultivations. The presence of 
the bacilli during the acute stage is constant, while when the patient is 
recovering they are less frequent. This examination of the stools and 
vomit, put up naturally or mixed with a drop of bouillon, is superior to 
the permanent stained preparations. It is not intended to supersede any 
further examination by means of cultivations. 
* Centralbl. f. Bakteriol. u. Parasitenk., xv. (1894) pp. 555-6. 
f Tom. cit., pp. 818-9. 
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