174 
Development of Hook-worms 
been added were negative after this date, but the untreated faeces 
and those to which 2 % salt solution had been added were positive 
for a further two days. The faeces treated with the large bulk of 
water remained positive up to the 21st day when the experiment was 
stopped. The control sample was completely dried up on the 10th 
day. 
The results will be readily seen in the following table; 
April, ! 
1915 
May, 
1916 
Date 
22 
23 
24 
25 
26 
27 
28 
29 
30 
i 
2 
4 
12 
No. of Days 
1 
2 
3 
4 
5 
6 
7 
8 
9 
10 
11 
13 
21 
1. 
Untreated faeces... 
+ 
+ 
+ 
-1- 
+ 
+ 
-1- 
+ 
+ 
+ 
- 
- 
- 
2. 
Faeces surrounded by rain 
water 2 c.c. to each 
gramme 
+ 
-1- 
+ 
+ 
+ 
-f 
-t- 
3. 
Faeces completely im¬ 
mersed in rain water 
15 c.c. to each gramme 
+ 
+ 
+ 
+ 
+ 
+ 
+ 
+ 
-t- 
+ 
+ 
T 
+ 
4. 
Faeces surrounded by 6 % 
salt solution . 
-f 
-1- 
+ 
-t 
+ 
-b 
_ 
_ 
5. 
Faeces surrounded by 4 % 
salt solution . 
+ 
-t- 
+ 
+ 
+ 
+ 
-f- 
6. 
Faeces surrounded by 2 % 
salt solution 
-t 
+ 
+ 
+ 
+ 
+ 
-f 
+ 
+ 
_ 
_ 
The conclusions to be drawn from these experiments are that, 
under the conditions described, solutions of salt (sodium chloride) even 
as strong as 6 % cannot be relied on to destroy hook-worm eggs in 
faeces in less than a week and that such solutions are not more effective 
than rain water under the same conditions. It must be noted, however, 
that in general the development both of the eggs and the larvae was 
greatly retarded by the presence of the salt solution, so that few of 
the eggs hatched in less than two days and most of the larvae did not 
reach the ensheathed stage till after ten days had elapsed. It must 
also be remarked that the mortality amongst the eggs and larvae was 
much greater than under normal circumstances and that in most cases 
only a few larvae, sometimes only one or two, were hatched, and a large 
proportion of these died within a few hours. 
In the case in which the faeces were entirely submerged in rain 
water the eggs were also very slow to develop and it was generally 
two to three days before the larvae hatched out and thereafter their 
growth was slow, many dying shortly after being hatched. 
In the control untreated faeces the eggs developed with considerable 
