78 (. OLIFFORD DOBELL. 
examination, it is diluted with a suitable fluid. Water will 
answer the purpose, or 0°75 per cent. NaCl solution. But 
in most cases I prefer to use a solution containing albumen, 
as the fixation of film preparations for staining is very much 
easier when albumen is present. JI have found the solution 
used by Grassi and Schewiakoff (23) for investigating intes- 
tinal parasites to be very suitable. It consists of 20 cc. egg 
albumen, 1 gr. NaCl, and 200 ce. distilled water. Another 
10 cc. of albumen improves the solution for films. If some 
of the diluted feces be kept for about five days a large 
number of monads can easily be obtained. 
Examination of the living monads was carried out in hang- 
ing-drop preparations, waxed round the edges, or in slides 
upon which a drop of the culture had been placed and covered 
by a coverslip—also carefully waxed round. I have also used 
the moist chamber of F. EH. Schultze with success. The best 
results were usually obtained with hanging-drop preparations. 
These are also the most easy to make into permanent 
preparations—by removing the coverslip, spreading out the 
drop, and fixing. 
In transferring drops of culture containing the monads to 
slides, etc., I always used a sterilised platinum loop or needle. 
A word must be said about the saline albumen solution 
which I have just described. It does not keep for more than 
a week or two, and must always be filtered before use as it 
harbours numerous micro-organisms. One of the most con- 
stant of these is a small Ameba, resembling A. limax, 
Duj., which lives on the surface, where it forms a slight 
scum. These organisms crawl actively about for some time, 
and finally encyst. 
Although with the illumination properly arranged, and with 
good lenses, etc., a very great deal of the structure and de- 
velopment of the monads can be seen in the unstained con- 
dition, nevertheless I have found that many of the changes 
undergone by the monads are more easily watched when they 
are stained intravitam. The intravitam stains which I have 
used are neutral red, Brillantkresylblau (Griibler), and 
