W. Nicoll 
169 
of suffocation of the eggs or starvation of the growing larvae. Absolute 
. desiccation is fatal to the eggs and larvae in all stages. The latter 
statement has led to some controversy, into which Looss enters very 
fully. My personal observations support his views on the subject. 
One matter must be referred to in Looss’ experiments. He makes 
mention of the fact that it is difficult to estimate the precise effect of 
any one particular agent or condition independently of other conditions. 
He lays special stress on the effect which decomposition or putrefaction 
may have in marring certain results and to this he attributes the apparent 
errors of certain other observers w'ho used material in its natural state 
in their experiments. Looss himself conducted most of his experiments 
with faecal material mixed with animal charcoal which to a certain 
extent prevents or arrests putrefaction. While realising, however, and 
insisting upon the fact that the majority of laboratory experiments are 
more or less artificial and unnatural he does not sufficiently emphasise 
the fact that his charcoal method is perhaps one of the most unnatural 
of all, for it provides an environment for the developing eggs much 
more favourable than they would as a rule obtain in nature. Under 
natural conditions decomposition and putrefaction set in with greater 
or less rapidity. In this case the decomposition products make their 
escape to some extent in the shape of gases or are washed out by rain, 
whereas in a laboratory experiment these products are largely retained. 
It may, therefore, be concluded that while laboratory experiments 
with untreated faeces are less favourable than natural conditions': 
methods such as the admixture of charcoal are on the side of being 
more favourable. 
Experimental InvestigatioNvS. 
The main object of the work detailed in this report has been to 
investigate and determine the action of common salt (sodium chloride) 
and other agents upon the development of hook-worm eggs and larvae 
in their various stages. 
The practical point in the investigations was to determine if salt 
would be able to kill the eggs within a short time (24 hours) and so 
avoid the possibility of their being washed into more favourable environ¬ 
ment by an intervening shower of rain or other cause. 
The experimental work has been extended over a period of two 
years partly in the hope that as great a variety as possible of patients 
and of conditions might be obt ined; partly for the reason that the 
