W. Nicoll 
173 
By far the most expeditious method, however, of cultivating hook¬ 
worm larvae is the dilution and washing method. 
In the course of the present experiments this was found of great 
value and, in fact, almost necessary. 
The technique is as follows: a small portion of faeces is thoroughly 
mixed with a small quantity of water in a dish, and the dish then filled 
up with water. After an interval of five or ten minutes the water is 
carefully decanted or pipetted off and the process repeated. Depending 
on the nature of the faeces from three to five washings are usually 
necessary. After the final washing a thin layer of water containing 
eggs and debris is left at the bottom of the dish and this is incubated 
at a suitable temperature. In the majority of cases numerous larvae 
hatch out within 24 hours. 
The above method is also useful for large amounts of faeces and 
although it is somewhat tedious it usually gives good results. 
Details of Experiments. 
I. The firsi series of experiments was conducted with the view 
of determining the effect of salt solutions of various strengths on the 
eggs and larvae of hook-worms. Strengths of 2, 4 and 6 % were used 
and the solution was added in the proportion of 2 c.c. to each gramme 
of faeces. As controls two portions of faeces were treated with rain 
water, in one in the proportion of 2 c.c. to 1 gramme, and in the other 
in the proportion of 15 to 1. In addition a portion of untreated faeces 
was cultivated. In the experiments in which rain water was used the 
smaller proportion of water did not cover the faeces, while the larger 
proportion covered them to a depth of about a quarter of an inch. 
In the case of the salt solutions the faeces were merely surrounded, not 
covered. Within 24 hours films and cultures were made from each 
bottle of the series. In every case the ova were found to be living 
and from each of the cultures living larvae hatched out. A day later 
the process was repeated and again living ova and larvae were obtained. 
The following two days witnessed the same result. On the fifth day 
all the cultures were positive except that from the 6 % salt solution. 
On the seventh day the only negative culture was that on which the 
smaller quantity of rain water had been used. On the eighth day the 
cultures from the two stronger salt solutions were both negative and 
no further larvae could be cultivated from them. The other cultures 
were still positive. The faeces to which a small quantity of water had 
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