1897 THE MICROSCOPE. 59 
may be quite harmless, when united with others they 
might become epidemic, and although it is not proven that 
they are disseminators of disease yet they must be re- 
garded with suspicion. 
Cerium Nitrate as a Bactericide.—It is stated that in 
proportion of one part toa thousand, cerium nitrate is a 
powerful bactericide and it is proposed to introduce it into 
therapeutics. 
Infection.— Never wet a lead pencil with the tongue or 
lipsas it may have been inthe mouth of some one else 
previously or may have otherwise collected microbes, 
How to Preserve Rotifers.—The rotifers can be pre- 
served with their wheels and other appendages extended 
according to M. Nicolas de Zograf, by narcotizing with 
cocaine hydrochloride, treating with osmic acid, then with 
weak crude wood vinegar, washed with water and dried 
by alcohol. 
PRA-C LIGAL Gt'G GES EON §., 
By L. A. WILLSON, 
CLEVELAND, OHIO. 
Fissidens taxifolius..-This is one of our smallest 
mosses. ‘The plants are two or three centimeters long. A 
sprig mounted beneath a 5-8 cover is a very pretty object. 
They must be mounted while moist for as soon as they are 
dry they begin toshrivel. Taken from water and placed 
in glycerine or glycerine jelly the ends and margins of the 
leaves curl up almost instantly. They would probably 
show to best advantage if moistened, spread out, then 
pressed until quite dry and mounted in balsam. Itis a 
novelty to see such small but beautiful and perfect leaves. 
A Home Made Eye-Piece Micrometer.—Beyond all 
doubt, a micrometer purchased froma reputable dealer is 
the best. However, many beginners would like to experi- 
ment in micrometry before they are prepared to makea 
purchase. ‘To effect the object, remove the field lens of 
