260 
NATURAE HISTORY. 
each side; tliey are covered with hair, and seem to have no 
eyes ; but there are two feelers on the head, which they make 
use of to find out the way they are to pass ; the head is very 
round, with two small sharp teeth, with which they inflict 
wounds that are very painful and dangerous. A sailor that 
was bit by one on board a ship, felt an excessive pain, and 
his lile was supposed to be in danger : however, he recovered, 
by the application of three roasted onions to the part ; and 
was soon quite well. Of this animal there are different 
kinds; some living, like worms, in holes in the earth ; others 
under stones, and among rotten wood ; so that nothing is 
more dangerous than removing those substances in the places 
where they breed. 
The G ally -worm differs from the scolopendra m having 
double the 'number of feet; there being two on each side, 
to every joint of the body- Some of these are smooth, and 
others hairy ; some are yellow, some black, and some brown. 
They are found among decayed trees, between the wood and 
the bark ; as also among stones that are covered with moss. 
They all, when touched, contract themselves, rolling them- 
selves up like a ball. Whatever may be their qualities in the 
tropical parts of the world, in Europe they are perfectly 
harmless; having been often handled and irritated without 
any vindictive consequences. _ ^ 
All these, as well as the scorpion, are supposed to be pro- 
duced perfect from the parent, or the egg; and to undergo 
no changes after their first exclusion. They are seen of all 
sizes ; and this is a sufficient inducement to suppose that they 
preserve their first appearance, through their whole existence. 
It is probable, however, that, like most ol this class, they 
often change their skins; but of this we have no certain 
information. 
The Leech, from its uses in medicine, is one of those 
insects that man has taken care to propagate ; but, ofa great 
variety, one kind only is considered rs serviceable. The 
horse-leech, which is the largest of all, and grows to four 
inches in length, with a glossy black surface, is of no use, as 
it will not stick to the skin ; the snail-leech is but an inch 
in length ; and though it will stick, is not large enough to 
extract a sufficient quantity of blood from the patient: the 
broad- (ailed leech , which grows to an inch and an half 
length, with the back raised into a sort of a ridge, will stick 
b u t° on very few occasions ; it is the large brown leech with 
a whitish belly, that is made use of in medicine, and whose 
history best merits our curiosity. 
