THE Microscope. BW 
EMPLOYMENT OF THE FREEZING METHOD In HistoLogy.—Dr. 
Axel Key and Professor Gustav Retzius reproduce in German 
an account of the freezing method which had been previously 
published by them in Swedish. The method is in many cases 
of great advantage, but it often causes certain abnormal appear- 
ances which, without due care, might be taken for actual fea- 
tures in the tissue examined; for example, in fine sections of 
tendon cut when frozen and fixed afterwards by means of per- 
osmic acid, a series of longitudinal canals were seen; and in 
sections of brain a regular system of lacuna communicating 
with each other appeared to exist which it was quite impossible 
to demonstrate by means of an injection. All these appear- 
ances, in fact, are produced by the freezing method itself; the. 
water contained in the tissues is driven out at the moment of 
freezing, and collects into lacunz where there is the least 
resistance. It is evident, therefore, that the greatest care must 
be exercised by histologists who make use of this method. 
EXAMINATION OF Urinary SepirMents.—Certain urines, 
especially concentrated urines and those passed in febrile con- 
ditions, deposit upon standing a considerable sediment composed 
chiefly of alkaline urates, and often deeply colored by uroery- 
thrine. The detection of the organized sediments, such as 
blood globules, epithelium, casts, etc., in such cases is difficult 
and often impossible. To facilitate the examination in such cases 
Mehu adds to such sediments, after they have subsided and 
after most of the urine has been removed, a small quantity of 
saturated aqueous solution of ordinary sodic phosphate. This 
dissolves completely the pigments and urates so that the sub- 
sequent examination of the sediment is comparatively easy. 
An excess of the sodic phosphate does do harm, but its addition 
frequently causes a precipitation of crystalline calcic phosphate. 
Mehu prefers this method of treatment to the common one in 
which the urates are dissolved with water. The latter delays 
the subsidence of the organized elements, and besides tends to 
soften and break them up.— Boston Med. Jour. 
Tenacity oF TuBERCcLE Bacrinur.—It has been doubted 
whether the sputa of tubercular patients, which are thrown on 
the streets and later mix with all kinds of dust, would ever 
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