172 
Development of Hook-wovnu 
fly larvae gained access were discarded. A few in which the number 
of fly larvae were small were allowed to pass after the larvae had been 
removed. 
One of the simplest and most convenient methods of rearing hook¬ 
worm larvae is to place small portions of faeces in Petri dishes along 
with a small quantity of water. Every 24 hours the water is poured 
off and replaced by a fresh quantity. The water removed is thoroughly 
mixed with tap water, sedimented and the supernatant layer decanted 
or pipetted off. The sediment containing the eggs and larvae is culti¬ 
vated and usually produces a good yield of larvae. In many cases, 
however, this method fails or gives poor results on account of the nature 
of the faeces, as already indicated. 
A modification of the method above-mentioned is to place the 
portions of faeces on a small pad of filter paper or blotting paper and 
surround it with water. This usually keeps the water somewhat cleaner. 
The method advocated by Looss is to mix the faecal material 
thoroughly with bone charcoal and spread the mixture evenly in Petri 
dishes. A firmly consistent mass is obtained which tends to become 
dry on the surface. When water is poured over this, at the end of 
three or four days a fairly copious supji^-of larvae can be washed off. 
Looss insists on the necessity of using bone charcoal. Wood charcoal 
is quite unsatisfactory. I have employed both materials in the cultiva¬ 
tion of human and canine ankylostonies. With wood charcoal the 
results have invariably been unsatisfactory, and indeed in the majority 
of cases entirely negative. Even with bone charcoal the results were 
extremely disappointing, and this method of culture was abandoned in 
favour of others which gave more immediate and satisfactory results. 
As Looss has pointed out it is not always easy to obtain a suitable 
variety of charcoal. 
A more satisfactory result was obtained by employing dry sterilised 
sand with which the faecal material was mixed in equal proportions. 
One of the most useful methods is to spread a thin layer of faeces 
over the bottom of a Petri dish. In the cover of the dish a piece of 
moistened blotting or filter paper is placed. At the end of four or five 
days the migrating larvae, attracted by the moisture, make their way 
up into the cover of the dish and can be collected in a very clean 
condition. 
Provided the upper half of the Petri dish can be made grease free 
and.the correct.amount of moisture obtained, the blotting paper is not 
essential. 
