(841 ) 
vaseline, the condensation takes place in small rounded droplets, 
which do not coalesce. Before use the needle is sterilized in a 
manner to be hereafter described. A micro-organism to be isolated 
is now sought at the edge of the so-called material-drop. The needle 
is moved up so that the end touches the edge of the drop near the 
cell that is to be isolated. 
Then, when the moist chamber is moved sideways the cell with 
a tiny droplet will be drawn out of the large drop. This cell is 
now taken up in the eyelet of the needle. This eye is then brought 
down somewhat so that it no longer touches the coverslip, and 
then the moist chamber is moved sideways, under a low power, so 
that the eyelet, by an upward movement, comes near to the edge 
of one of the sterile drops and deposits the isolated cell, in a small 
drop, once more on the coverslip. 
Under the high power this small drop with the cell is moved 
into the sterile drop, in which the culture is to be made, the so- 
called culture-drop. 
The glass is then placed on an ordinary moist chamber which is 
kept at the required temperature. If the culture drop is solid, then 
the colony grows on its edge, and with the strongest power its 
development can be followed from the beginning. If the culture 
drop is fluid the colony generally spreads itself over the whole drop. 
So much for an outline of the method. 
Of the improvements made since my last publication, I mention in 
the first place, that instead of the isolation apparatus hitherto made 
by the firm of D. B. Kacensar Sr. in Utrecht for £ 5 (without 
needles) I have constructed a simplified arrangement, of which the 
price with three isolation needles amounts to £2. 1.8. The objection 
that the needles were not obtainable commercially is thus removed. 
Formerly I used one pointed needle, and three ending in an eye: 
one very small eye of 9m in diameter, a medium one of 30 u, and 
a large one of 50 u diameter. Experience has shown me, that the 
smallest eye, which was the most difficult to manufucture, must be 
abandoned. It was intended for the isolation of bacteria; with a 
somewhat greater eye this succeeds much better, and the following 
3 needles suffice: a pointed one, an eye of about 30 u in diameter 
for bacteria and small yeast cells or spores and an eye of + 50 u 
in external diameter for larger cells '). 
With the older apparatus there was a needle at each side of the 
1) The above mentioned measurements are average values; the diameter and 
thickness of thread can, without objection, be somewhat larger or smaller. 
55* 
