64 NATURAL HISTORY OF BRITISH FRESH-WATER LEECHES.
mix them with eyesel; then use to rub the place therewith where you
would have hair grow no more, and there will no hair grow in that place."
A curious statement occurs in Bullein's The Booke of
Simples (Bullein was a native of the Isle of Ely and lived early
in the reign of Henry VIII.).
"Horseleches are wholesome to draw forthe foule blood, if they are
put into a hollow rede, and one of their endes cutte of, whereby the blood
maie run forthe."
The old writers gravely warn people against the danger of
swallowing Leeches. Pliny states that they were frequently
administered to an enemy. It seems rather difficult to under-
stand in what circumstances such a dose could be given without
the victim knowing it. Several cures are prescribed, such as.
salt-water, vinegar and holding a moist sponge in the mouth.
One of the methods recommended seems original. The patient
is to get into a hot bath and hold cold water in his mouth, the
Leech being supposed to be attracted by the latter.
Leeches were at one time considered to show changes of the
weather, and were used as barometers. Dr. J. Forster says that
Leeches confined in a glass of water by their movements fore-
tell rain and wind, before which they seem much agitated,
particularly before thunder. Dr. G. Johnston (33) says that
he made many experiments to test this assertion, and came to
the conclusion that such forecasts were not reliable.
Systematic position and general outlines of structure.-
The class Hirudinea (Leeches) is a well-defined one, and is nearly
allied to the Oligochaeta, to which the Earth-worms belong.
Their worm-like form and segmentation are characters which
suggest an affinity with the Oligochaetes, but Leeches are dis-
tinguished, as a rule, by the possession of two suckers, one at
each end of the body, a more oval outline when viewed from
above, and a dorso-ventral flattening of the body. It is in-
teresting to note that the members of a family of Oligochaetes 
—the Discodrilidae—are parasitic in habit, one species being
found on the gills of crayfish.
The number of transverse rings which cross the body exceed
the number of somites or body segments, and the number and
arrangement of rings and somites are of great importance in
classification. The extent of each somite can usually be defined
by noting peculiar external markings on the dorsal surface,