HIR 
preserved for several months, almost with- 
out coagulating:, and proves a store of pro- 
vision to the animal. The nutritious parts, 
pure and already digested by animals, have 
no call to be disengaged from the lietero- 
geneous substances : nor indeed is there an 
anus discoverable in the leech ; mere trans- 
piration seems to be all that it performs, 
the matter fixing on the surface of its body, 
and afterwards coming off’ in small threads. 
Of this an experiment may be tried, by 
putting a leech into oil, where it keeps alive 
for several days : upon being taken out, and 
put into water, there appears to loosen from 
its body, a kind of slough, shaped like the 
creature’s body. The organ of respiration, 
though unascertained, seems to be situated 
in the mouth ; for if, like an insect, it drew 
its breath through vent-holes, it would not 
subsist in oil, as by it they would be stopped 
up. 
It is only the first species that !s used in 
medicine, being applied to the skin in or- 
der to draw off blood. With this view they 
are employed to phlebotomise young chil- 
dren. If the leech does not fasten, a drop 
of sugared milk is put on the spot it is 
wished to fix on, or a little blood is drawn 
bv means of a slight puncture, after which 
it immediately settles. The leech, when 
fixed, should be watched, lest it should find 
its way into the anus when used for the he- 
morrhoids, or penetrate into the oesophagus 
if employed to draw the gums, as it would 
make great havoc in the stomach or intes- 
tines. In such a case, the best and quickest 
remedy is to swallow some salt; which is 
the method practised to make it loose its 
hold when it sucks longer than was in- 
tended. 
H. sanguisuga, horse-leech: elongated, 
olive-brown, with an ochre-yellow marginal 
band : found in .stagnant waters, ditches, 
and ponds: from four to six inches long: 
body above dull olive-black, with an ochre 
margin on each side; beneath paler, with 
sometimes a few black spots : tail thicker 
than the head. This species sucks blood 
with great avidity, and in large quantities. 
H. viridis: body depressed, oblong, green, 
with a transparent margin and pointed tail. 
This species has been described by Dr. 
Shaw in the “ Transactions of the Linnaean 
Society :” it inhabits clear cold waters, is 
about the eighth of an inch long, and like 
most of the genus has a power of reproduc- 
tion almost equal to that of the polype ; for 
if the animal be divided in every direction, 
the parts will become perfect animals, and 
HIR 
may be again divided and again reproduced. 
It is of a grass-green colour, with a trans- 
parent border all round. H. geometra, or 
geometrical leech: body filiform, greenish, 
spotted with white ; both ends dilatable, 
and equally tenacious. It inhabits fresh 
waters : moves as if measuring like a com- 
pass, whence the name : it is found on trout 
and other fish, after the spawning season. 
HIRUNDO, the swallow, in natural his- 
tory, a genus of birds of the order Passeres. 
Generic character : bill short, depressed at 
the base, small at the point, and a little 
bending; nostrils open ; tongue short, broad, 
and cleft ; wings long ; legs short ; tail, in 
general, forked. These live almost perpe- 
tually in the air, and perform in it every act 
of their nature. They subsist upon the in- 
sects with which that element abounds, and 
which they catch on the wing with the most 
admirable dexterity ; and for this purpose 
they are furnished with a most extraordinary 
power of distending their jaws. The ser- 
vice they perform to man by their incessant 
assiduity in this work of destruction is not 
lightly to be appreciated, and those who 
observe the crowded population of the at- 
mosphere through the beams of a summer 
evening, will easily be led to believe, that, 
but for the interception of incalculable my- 
riads of insects by these birds, the annoy- 
ance of man by these minute animals would 
be highly distressing, and perhaps almost 
intolerable. The celerity of this tribe of 
birds is truly astonishing, and that union of 
flexibility and speed which they exhibit in 
pursuit of their prey, or with which they 
elude the grasp of their enemies, is highly 
remarkable and interesting. Their man- 
ners are eminently entertaining and social. 
They fix their nests to the habitations of 
man, and are not only extremely useful in 
some respects, but perfectly inoffensive in 
all. Though so much within the observa- 
tion of man, some circumstances of their 
economy have hitherto completely baffled 
the curiosity of the most vigilant observer. 
Various opinions have been formed of the 
state in which they exist during the time of 
their disappearance ; some imagining them 
to lie torpid, in the banks of rivers, or in 
decayed trees, or in ruined edifices or 
vaults ; and others, that they retire for the 
wiuter from the air to the water, lying in 
immense clusters, like swarms of bees, at 
the bottoms of rivers. Particular facts are 
on record, by respectable testimony, in fa- 
vour of both these hypotheses. It is also 
attested, on similar authority, that migra- 
