TREATMENT OF DISEASES CAUSED BY WORMS                43

Castor oil should be used, as a rule, only in those cases in which it can be given
with the anthelmintic. If the purgative is to be given an hour or two after the
anthelmintic, it is advisable to use the fast-acting purgatives, such as salts.

      Macht has shown that salts, by virtue of the well-known salt action, lessen
or inhibit the absorption of drugs given with them. They are, therefore, contra-
indicated for use with drugs from which a systemic effect is desired. On the other
hand, the salt action is of value in connection with anthelmintics for removing
worms from the digestive tract proper, since systemic action is not desired from
these drugs, and it is desired to confine their action to one exerted within the
lumen of the digestive canal. In using salts, the present tendency is to substitute
sodium sulphate for magnesium sulphate on the ground that sodium is less toxic
than magnesium, and does not have the same antagonistic action with the blood
calcium. Experience in human medicine shows that saturated solutions of salts
produce more nausea and other bad effects than do weaker solutions, and it is
advisable to make a saturated solution and dilute it with twice its bulk of water
for use. Salts are most readily used in veterinary medicine in patients which do
not vomit, or vomit with difficulty, such as ruminants and solipeds. Dogs show a
disposition to vomit after salts, although this tendency can be overcome, and salts
can be used in dog practice.

      Liquid petrolatum in some form is often used in connection with anthelmintics,
and may be satisfactory in the treatment of such animals as the horse. Tests
show that it is unsatisfactory in combination with chenopodium in the treatment
of dogs, as it lowers the anthelmintic efficacy and gives inadequate protection
against the effects of the drug on the dog. A more extended study should be
made as to the effect of varying the amount of petrolatum, as this may be a factor
in determining the results. Olive oil is sometimes used in connection with anthel-
mintics, but experience indicates that this is usually bad practice. Olive oil is one
of the substances which remain longest in the stomach, and in combination with
chenopodium there results a decided inflammation of the stomach from the prolonged
irritant action of the chenopodium at this point. There is also a resultant fall in
efficacy due to the absorption of the drug in the stomach.

      In veterinary medicine the value of our anthelmintics must be ascertained
by critical testing if we are to have dependable information. In critical testing,
animals are given measured doses of the drugs to be tested, all worms passed for
a suitable period are collected, identified, and counted, and the animals are then
killed, and all worms present post-mortem are collected, identified, and counted.
These two sets of figures give the total numbers of worms of each kind present at the
beginning of the experiment, and one can compute rather accurately the percentage