178 
Development of Hook-ivorms 
of hook-worm eggs is completely arrested within 24 hours and the eggs 
do not hatch. When the quantity of salt, however, is reduced to one- 
quarter or a third of the weight of the faeces a few eggs may survive 
its influence for two days and give rise to larvae. This amount of salt 
is sufficient to kill all the eggs within three days. 
IV. This series of experiments was similar to the last but with 
material from another patient and with much smaller quantities of salt. 
The amounts of salt used were: 
0-19, 0-1, 0-05 and 0-025 g. {i.e. 19%, 10 %, 5 % and 2-5 %) of the 
weight of faeces. These may be numbered 1-4. An untreated C(?ntrol 
sample (No. 5) was also used. 
The results of this series are of considerable interest. From Nos. 1 
and 2 no larvae could be reared and examination of the material at 
the end of 48 hours showed that all the eggs were dead. From No. 3 
larvae were reared up till the end of the third day. None could be 
obtained on the fourth day, but on the fifth a couple of larvae were 
hatched out. After this no further larvae coidd be produced. ,From 
No. 4 larvae were produced continuously for five days but not thereafter. 
On the first two days they were obtained in considerable numbers but 
on the following three days they were few and feebly developed. From 
the control numerous vigorous larvae were produced for over a week. 
Throughout this experiment it was noticeable that the larvae 
reared from Nos. 3 and 4 were slow in hatching and developing when 
compared with the rapid hatching and vigorous growth of those from 
the control. The only exception was in the case of No. 4 from which, 
on the second day, a very good brood of larvae was produced. This 
circumstance may be accounted for by the possibility that the salt 
had not been mixed in thoroughly and that a small part of the faeces 
had remained unaffected by it. This would show, as some of the 
previous experiments also do, that .the effect of the salt spreads very 
slowly and that it is essential that it should be brought into intimate 
contact with the whole mass of the faecal material. 
The larvae in each of these cultures were kept under continuous 
observation for eighteen days. The larvae in the control cultures 
pursued a normal course and were fully developed and ensheathed 
within six days. The larvae in the other cultures, however, had a 
greatly retarded development. They did not reach their first moult 
till about the fourth day, and little increase in size could be observed 
during the next two or three days. Thereafter, however, they began 
