REP 
REP 
vs’iiich lived and grew larger in a vessel of 
water into wliicli he put it. These small 
bodies are easily divided, and very readily 
complete themselves again, a day usually 
serving for the production of a head to 
the part that wants one ; and, in general, 
the smaller and more slender the worms 
are, the sooner they complete themselves 
after this operation. When the bodies of 
the large worms are examined hy the mi- 
croscope, it is very easy to see the appear- 
ance of the young worms alive, and moving 
about within them; but it requires great 
precision and exactness to he certain of 
this; since the ramifications of the great 
artery have very much the appearance of 
young worms, and they are kept in a sort 
of continual motion by the systoles and 
diastoles of the several portions of the ar- 
tery, which serve as so many hearts. It is 
very certain, that what we force in regard 
to these animals, by our operations, is done 
also naturally every day in the brooks and 
ditches where they live. A curious ob- 
server will find in these places many of 
them without heads or tails, and some with- 
out either ; as also, other fragments of va- 
rious kinds, all which are then in the act of 
completing themselves ; but whether acci- 
dents have reduced them to this state, or 
they thus purposely throw off parts of their 
own body for the reproduction of more 
animals, it is not easy to determine. They 
are plainly liable to many accidents, by 
which they lose the several parts oftheir body, 
and must perish very early if they had not 
a power of reproducing what was lost ; 
they often are broken into two pieces, by 
the resistance of some hard piece of mud 
which they enter; and they are subject 
to a disease, a kind of gangrene, rotting off 
the several parts of their bodies, and must 
inevitably perish by it, had they not this 
surprising property. 
The reproduction of several parts of lob- 
sters, crabs, &c. is one of the greatest 
curiosities in natural history. It seems, 
indeed, inconsistent with the modern sys- 
tem of generation, which supposes the ani- 
mat to be wholly formed in the egg ; that, 
in lieu of an organical part of an animal 
cut off, another should arise perfectly like 
it : the fact, however, is too well attested 
to be denied. The legs of lobsters, &c. 
consist each of five articulations ; now when 
any of the legs happen to break by any acci- 
dent, as by walking, &c. which frequently 
happens, the fracture is always found to be 
at the suture near the fourth articulation ; 
VOL. V. 
and what they thus lose is exactly repro- 
duced in some time afterwards ; that is, a 
part of the leg shoots out, consisting of four 
articulations, the first vvhereof lias two claws, 
as before ; so that the loss is entirely re- 
paired. 
If the leg of a lobster be broken off by 
design at the fourth or fifth articulation, 
what is thus broke off is always repro- 
duced. But if the fracture be made in the 
first, second, or third articulation, tiie re- 
production is not so certain. And it is 
very surprising, that, if the fracture b& 
made at these articulations, at the end of 
two or three days, all the other articiila- 
tions are generally found broke off to the 
fourth, which, it is supposed, is done by 
tlie creature itself, to make the reproduc- 
tion certain. The part reproduced is not 
only perfectly similar to that retrenched, 
but also, in a certain space of time, grows 
equal to it. Hence it is that we frequently 
see lobsters, which have their two large 
legs unequal in all proportions. And if the 
part reproduced be broken off, a second 
will succeed. 
REPTILIA, in natural history, an order 
of Amphibia, the character of wliich is, that 
they breathe through the mouth ; have feet, 
and flat naked ears without auricles. There 
are five genera ; viz. 
Draco Siren 
Lacerta Tertudo. 
Rana 
REPULSION, in physics, that property 
in bodies, whereby, if they are placed just 
beyond the sphere of each other's attrac- 
tion of cohesion, they mutually fly from 
each other. Tims, if an oily substance, 
lighter than water, be placed on the sur- 
face thereof, or if a piece of iron be laid 
upon mercury, the surface of the fluid will 
be depressed about the body laid on it : 
this depression is manifestly occasioned by 
a repelling power in the bodies, which 
hinders the approach of the fluid towards 
them. But it is possible, in some cases, 
to press or force the repelling bodies into 
the sphere of one another’s attraction ; and 
then they will mutually tend towards each 
other, as when we mix oil and water till 
they incorporate. Dr. Knight defines re- 
pulsion to be that cause which makes bo- 
dies mutually endeavour to recede from 
each other, with different forces, at dif- 
ferent times ; and tliat such a cause exists 
in nature, he thinks evident for the follow- 
ing reasons. 1. Because all bodies are 
O o 
