170 
Decelopitient of Hooh-irornis 
number of patients available was not very great and of these only a 
small proportion were suitable for experimental purposes. 
The material in nearly every case has come from hospital patients, 
and as the chief aim in such cases was curative, more than one sample 
of untreated faeces could rarely be obtained and in many cases even 
that could not be jtrocured. No material was used from patients who 
were receiving treatment. A few samples of faeces were obtained 
from orphanage children and from school children, but these were, as 
a rule, unsatisfactory, being too small in quantity to permit of an 
extensive series of experiments and being moreover of uncertain age. 
In most of these cases the eggs had undergone a considerable amount 
of development. 
During the course of these two years only thirty-three cases of 
hook-worm infection have been submitted to me for examination—but 
in fifteen of the cases the faeces were not obtained until after treatment 
had been started. Of the remainder only twelve were found suitable 
for experimentation. In five of these cases more than one series of 
experiments was undertaken. 
These experiments being so few in number and the factors involved 
being so complicated, it follows that the results, even in cases where 
they appear definite, cannot altogether be regarded as of general applica¬ 
tion. The nature and composition of the faeces employed, their age, 
the variations in the temperature during the experiments, are all factors 
which could not be accurately determined. 
According to Looss (p. 371) the conditions which generally prevail 
in laboratory cultures are much less favourable to the larvae than 
natural conditions. It must be remarked, however, that this is not 
necessarily the case, for in a covered laboratory culture the supply of 
moisture is kept relatively constant and falls off only very slowly: the 
temperature is also more uniform; while the supply of air in suitably 
selected vessels, except when kept in a closed incubator, is quite 
sufficient for the full development of the eggs and larvae. If the cultures 
are properly manipulated there is every reason to expect that a con¬ 
siderable proportion of the larvae will survive for at least a year. 
Technique op Experiments. 
The faeces, having been obtained as fresh as possible and examined 
for the presence of hook-worm eggs, were divided into separate portions, 
usually 2-4 grams in weight. Several small glass vessels were prevdously 
cleansed and accurately weighed. Into each of these a portion of 
