ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 
531 
especially of Monocotyledons as Allium canadense, or among Dycotyle- 
dons Podophyllum peltatum. The latter is especially favourable for 
showing the early stages, because of the small number (about ten) of the 
nuclear segments. 
Dehydration and clearing up of Algae.* — The following method, 
described by Dr. E. Overton, neither requires complicated apparatus nor 
demands a great expenditure of time, in obtaining a result more favour- 
able than is usually expected when dealing with such delicate objects as 
Algae, which shrivel or crumple up when transferred from one reagent 
to another. 
The object, previously fixed and stained, is placed in a not too large 
quantity of 10 per cent, glycerin. Here it remains in an open vessel 
until the glycerin has given off nearly all its water. The objects are then 
transferred to absolute alcohol. Their further treatment depends on 
the nature of the clarifying medium. If turpentine, oil of cloves, or the 
like is to be employed, the object should be placed in a watch-glass, 
containing a 10 per cent, solution of the oil in absolute alcohol. The 
watch-glass is placed in a large covered vessel, on the floor of which are 
some pieces of calcium chloride to absorb the alcohol. In this way the 
objects are gradually impregnated with the pure oil, whereupon they 
may be transferred to dilute balsam. If before the objects be placed in 
the ethereal oil and alcohol mixture, they be passed through chloroform, 
this step will avoid the too great extraction of the staining by the spirit. 
Should xylol be preferred for clearing up, then in the larger vessel 
pure xylol is placed as well as in the watch-glass. By a process of diffu- 
sion the inner vessel will ultimately contain almost pure xylol. By means 
of this method the most delicate algae may be mounted in balsam without 
crumpling. 
Amplification required to show Tubercle Bacilli.f — When properly 
stained and prepared, the bacillus tuberculi can be readily recognized 
with a good 1/5 objective and a 2-in. eye-piece, normal tube- 
length, or, roughly speaking, an amplification of 250 diameters. We 
do not think that it could be done much below this amplification, 
though the sharpness of vision of the observer, his acquaintance with 
the object, and the excellence of his objective would be important factors 
in settling the question. A 1/4 objective with a 2-in. eye-piece, normal 
tube-length, gives an approximate amplification of 200 diameters. 
To be seen and diagnosed for certain, the bacillus tuberculi in 
urine or water must be prepared for examination by following the well- 
known technique in such cases (fixing, staining, bleaching, and mounting). 
No person who has any regard for his reputation as a microscopist 
would undertake to diagnose for certain bacilli of tubercle from other 
similar forms existing in water, urine, or any other medium whatever, 
whether with a magnification of 200 or 2000 diameters. The property 
of taking certain aniline stains, and retaining them so firmly that even 
nitric acid, diluted with only three volumes of water or alcohol, will not 
bleach them, is one peculiar to the tubercle bacillus, and shared, as far 
as we know, by the bacillus of leprosy only. This test, along with 
* Zeitschr. f. Wiss. Mikr., vii. (1890) pp. 11-13. 
t Amer. Mon. Micr. Journ., x. (1889) pp. 277-8; from ‘National Druggist.’ 
