22                                               Surra.

Solutions of atoxyl up to 15 per cent. can be given
intravenously and subcutaneously without injury to the
tissue.

In our experiments we found that the lower dilutions
were preferable, as they were absorbed more readily and
caused less irritation at the seat of inoculation. For horses
a 4 per cent. solution and for small animals, a 1 per cent.
solution was adopted. The horse can tolerate 5½ gms. of
atoxyl per 500 lbs. body-weight, administered intravenously.
Subcutaneously somewhat less than double this amount can
be administered without any toxic effect.

In the guinea-pig 6 cgms. per 500 gms. body-weight is
the maximum amount which can be injected subcutaneously
with safety. In the treatment of Surra with atoxyl it is
not necessary to use large doses. About a quarter of the
toxic amount is sufficient. The dose should have the effect of
causing the trypanosomes to disappear from the peripheral
circulation.

If, on the day following the administration of atoxyl, the
trypanosomes still persist in the blood, the quantity of
atoxyl should be slightly increased and a second injection
made. The solutions of atoxyl should be freshly prepared.
The orpiment is best given in form of bolus and after the
animal has fed. Care must be taken that the ball or pill is