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THE INDIAN JOURNAL OF VETERINARY SCIENCE AND ANIMAL HUSBANDRY. [V, III
There are probably few indeed who would not gladly exchange treatments
based upon the utilisation of the normal physiological processes for the use of
anthelmintics. The latter are rarely satisfactory. The results of the immense
amount of labour expended upon them have been very meagre. Carbon tetrachlo-
ride is perhaps at once the most powerful and the most dangerous of them. Copper
sulphate is useful only against Haemonchus contortus. There are a few others
the effects of which are erratic and unreliable. All anthelmintics are expensive
and their administration requires skilled labour. Their effects can only be
temporary, so that they must be continually administered. The intelligent farmer
may be willing to undertake this, and he may do it efficiently, even when many
thousands of animals have to be so treated, but the majority of farmers would
certainly be glad if they were told that anthelmintics were no longer required.
There is also always the problem of how anthelmintics should be best adminis-
tered. When they are to be given by the mouth, the obstacle presented by the
three oesophageal dilatations preceding the ruminant stomach largely destroys
their efficacy and most of the domesticated animals we wish to treat are ruminants.
We are slowly learning something about the mechanism of this " stomach," so
that we may feel more certain than we did that some, at any rate, of the drug
we give by the mouth does at least enter the abomasum or true stomach, and enters
it unchanged, even if we have no such certainty when farm birds are being treated,
that we have surmounted the similar obstacle presented by another oesophageal
dilatation, the crop. But even when the drugs we give do enter the abomasum
unchanged, we cannot say that they reach the nematodes in the intestines un-
changed ; and we have no knowledge of how they act upon these.
We need, in fact, much more work upon the effect of chemical substances
upon " adult " nematodes and upon their larvae. The possible importance of such
work is indicated by the writer's observations on the remarkable effects upon the
infective larvae of the solutions mentioned above containing mineral and
organic sulphides. These observations suggest that sulphides might be used for
treatment. If, as Mueller (1929) suggests, the cuticle of nematodes is an albu-
minoid or is allied to the albuminoids, these sulphides may have a solvent action
on it similar to their action on keratin, so that they would enter the worms readily ;
or enable other toxic substances to do so. They could, perhaps, therefore be used
either for their own toxic effect,or as a preliminary treatment to prepare the way
for other drugs. H 2 S can be produced by B. coli in media containing such organic
sulphides as cystein hydrochloride, so that it may prove possible to add to the diet
of the host animals some ingredient of this kind, from which the normal bacteria
of the intestine would produce a suplhide toxic to the parasites. It is not likely
that it would be produced in great amount, so that its effects might not be power-
ful, but they would for that reason be less likely to harm the host and would
control the parasite all the more efficiently because they would be continuously