1807. | 
ftrattuve of the flefly difews, which per- 
forms the office of fucker, cannot eally 
be afcertained, for when the fkin which 
covers it is removed, we oblerve ouly 
{ume miunute fibres interwoven in dif- 
ferent directions. In confequence of the 
racuum, formed by the contraction of the 
difcus, the animals are fixed by the pref- 
fure of a column of air, correfponding to 
their diameter. 
They {wim like eels, by a ferpentine 
motion. When they would change their 
place without fwimming, they begin by 
fixing their body at one of the extremi- 
ties, by means of the fucker that termi- 
nates it. The circular mufcles of the 
ikin then fevarately aét, by which the 
body is elongated, by diminifhing its di- 
ameter. When the free extremity has 
reached the place to which the animal is. 
defirous of extending it, it is applied and 
made faft to that {pot by the fucker, and 
becomes the fixed p joint of a new motion, 
The animal, having now removed the 
fucker firft made ufe of, draws it, .by the 
operation of the lougitudinal fibres of the 
fkin, towards the other fucker, and pro- 
ceeds, in this manner, to fix each extre- 
mity alternately. Thefe motions are ex- 
ecuted with confiderable rapidity. 
The mouth is a triangular opening, 
having three firong and thar p teeth, which 
meet in the centre, and are capable of 
piercing not only the human {kin, but 
even the tender parts of that of the horfe 
or ox. At the bottom of the mouth there 
is a kind of flefhy prominence, in which 
the tube terminates that conveys the 
blood from the triple wound, formed: by 
the teeth, mto the ftomach of the animal. 
The ftomach confiis of ‘a great number 
of nembranous bags, fur nifled with fmall 
valves, in which hided has fometimes 
been known to continue for mauy months 
without being coagulated. As none of 
the leeches have more than one principal 
“orifice in their bodies, it is extremely 
probable, fxys Morand, who has pub- 
lithed a Memoir refpeéting thefe animals, 
that all thofe particles of the blood they 
fwallow, which do not affift in nourifhing 
their bodies, may pafs off by tranfpira- 
tion, and thus term the vifcous fluid 
which exudes through the fkia. This 
fluid may be obferved in blackifh fila- 
ments, im water in which leeches are 
kept. 
It appears that leeches refpire through 
their mouth. The greater part are fur- 
nithed with organs of vifion, varying in 
number, (according to the fpecies,) frout 
gae to eight, dn many of them, howe 
Obfervations on the Natural Hiftory of Leeches. 321 
ever, no eyes'are to be feen, even with 
high magnifying powers. 
‘If a leech be cut in two, that part 
which contains the head will continue in 
life, and, atter.a tmie, greater or lefs ac- 
cording to the featon, will become a new 
animal, differing im no refpect whatever 
from others of its fpecies. It thould ap- 
pear from this fact, and from fome other 
obfervations, that leeches increafe in lize, 
not only by the developement of their 
parts, but likewife by augmentation, that 
is to fay, that old leeches have a vreater 
number of nufcular rings than the young 
ones. 
Teeches are-furnifhed with the organs 
of both fexes; and are viviparous or pro- 
duce their offspring alive. In the fame 
manner as in the fnails, their generative 
organs are fituated near the cefophagus. 
They ufually breed about the beginning 
of the fpring, and as many as feventy 
young-leeches have been counted in the 
body of an old one. 
Some fpecies of leeches are found im 
almoft all waters; but the greater part of 
them prefer fuch as are muddy, and 
affurd growth to numerous aquatic plants. 
They are common throughout the whole 
of Europe, butlefs fo in the fouthern thar 
the northern parts. The duration of their: 
life has not been afcertained; but, be 
fides the general caufes of mortality. to 
which they are fubject, fuch as the drying 
up, but more bball the putrefac- 
tion (during the heats of fummer,) of the 
waters that they inhabit, they have many 
enemies, which are m continual purfuit 
of them for food. , Thefe are chiefly dif- 
ferent {pecies of filh and water-fowl ; but 
there are’ alfo' numerous larvae of water- 
infects, and even of perfect infects whieh 
prey upon them. Even the leeches 
themfelves deftroy one another. Thofe 
that have been long without food fall, 
without mercy, upon fuch as are gorged, 
and fuck out of theit bodies the juices 
with which they are replenifhed. This 
circumftance has been particularly re- 
marked by Vauquelin and fome other 
naturalitts. 
Thefe amimals will not only fuck the 
blood of each other, and of quadrupeds 
and fithes, but will faften upon the larve 
of infects, and numerous kind of vermes, 
&c. that inhabitthe fame waters in which 
they live, Whenever they have oppor- 
tunity, they gorge themfelves tll their 
ftomach will contain no more. On the 
contrary, when food is not to be had, 
they are able to fupport life for many 
months without receiving any nutriment. 
This 
