616 
GILBERT B. JOHNSON. 
sions. While sharing with the latter medium this advantage 
over peptone, the new form of medium has also certain draw- 
backs ill common with it. The body-wall, as it becomes more 
and more opaque in the course of deca}^, makes a dark back- 
ground on which it is difficult to distinguish the nematodes 
in the culture. Occasionally, also, the whole contents of the 
culture develop an evil odour or in addition become clouded 
over with a dense scum, not only rendering examination impos- 
sible, but also causing the death of all the nematodes. But the 
chief drawback, and the one which rendered it necessary to 
discontinue the use of the strip method, was the presence of 
nematodes which were found infesting the medium in certain 
cases even after the exercise of the utmost care in attempting 
to remove them all. 
A third medium, designed to avoid the disadvantages of 
its predecessors, has been devised and is prepared as follows : 
Several Lumb. terrestris arekilled and then cleaned by 
the removal of the gut. They are put with some water into 
a test-tube, which is then plugged with cotton-wool, heated in 
a steamer and kept at boiling-point for about two houi’S. 
The opaque broth is decanted and filtered. The almost clear 
resultant liquor, in which putrefaction very soon commences, 
is inoculated with the bacteria, which in the natural state are 
associated with the decay of the worm in the soil. For this 
purpose a freshly killed Lumb. terrestris is allowed to 
decay in a small quantity of water to which a little earth is 
added, and a spot of this fluid, carefully examined under the 
microscope to get rid of any nematodes in it, is added to the 
clear liquor before the bacteria from the air have had time to 
multiply in it. The liquor soon becomes cloudy with the 
growth of the soil bacteria and is then ready for use. This 
worm extract has been used for all the most recent cultures. 
It forms on the whole an excellent food-medium. Certainly 
it is the best that has yet been devised. Like the body- wall 
medium, it is more nutritious than peptone, and produces 
adults of large size. Over decaying body-wall it possesses 
the twofold advantage (for the sake of which it was devised) 
