H. D. SRIVASTAVA                                        315

may be applied around the anus to relieve pruritis, and to kill adhering eggs.
Oil of turpentine is also an effective treatment when given in a dose of 60 c.c.
for a l,000-lb. animal immediately preceded or followed by a litre of raw
linseed oil. Prophylaxis is a matter of sanitation with reference to stables,
feed and water, besides the proper disposal of manure.

                              STRONGYLES

Horses are infested with many kinds of strongyles, and often with large
numbers of several species. It is rare to find a horse entirely free from these
parasites, and on the other hand it is common to find them heavily infested.
Over 40 species of these worms are known to occur in horses, mules and
donkeys. Some of them are blood suckers while others are not, but the in-
festation is usually a mixed one. The general symptoms of strongylosis may
be taken to be caused by all of them collectively, though the blood sucking
species are naturally the more harmful. The equine strongyles may be
divided into two broad groups. The large strongyles which are also commonly
known as blood-worms, red-worms, sclerostomes or palisade worms and the
small strongyles which are much smaller in most cases than the red-worms,
though some of these may be almost as large.

      THE LARGE STRONGYLES OR PALISADE WORMS

Three species of the large strongyles are of common occurrence in the
colon and caecum of equines. The worms are red in colour and are frequently
found firmly attached to the wall of the gut by means of a rather formidable
buccal capsule. The three-toothed strongyle— Strongylus equinus—is the
largest of the three species ; the toothless strongyle— S. edentatus—is some-
what smaller and the single-toothed strongyle— S. vulgaris—is the smallest.

The life-cycle of strongyles is direct in all known cases (Plate XXV, fig. 1).
The eggs are laid in the intestine and are passed out with the droppings. The
eggs, as well as the larvae developing in them, require oxygen, moisture and
a suitable temperature for their development to the infective stage. Under
favourable conditions embryos or larvae in the eggs develop rapidly and hatch
in a day or so. The larvae move about freely in the droppings and feed on
bacteria and other material which they find there, and grow and moult. After
the first ecdysis they resume their feeding and in due course—about a week—
moult a second time, but this time they do not cast the old cuticle but retain
it as a protective sheath. The larva is now in the infective stage. The
infective larva is extremely resistant to adverse conditions, especially dry-
ness. The infective larva does not feed but lives on the food granules stored
in its interstitial cells. As soon as these are exhausted it dies. The larva
gains entrance into the host by being ingested with food or water, its habits
are such that they increase the possibility of reaching a host. These habits
are due to response to external stimuli. The larva is negatively geotropic
and crawls up blades of grass or other objects. It is heliotropic to a mild
light, but is repelled by strong sunlight. There is a certain amount of response