his Hand was variously distributed and moved to and fro ; and about G there appeared a
pretty large white Substance moving within the Thorax. This somewhat resembled a
Bladder, contracting and dilating upwards and downwards from the Head towards the Tail.
Across the Breast were many small milk-white Vessels running between the Legs, and
sending to them innumerable minute Branchings, which no doubt are Veins and Arteries ;
for in most Insects the Juices analogous to Blood are white.
The Louse has six Legs, which are strongly joined to the Thorax ; and for each Pair a
kind of Division appears thereon, as e e e. They are covered with a very transparent
Shell, and jointed exactly like the Legs of a Crab or Lobster. Each of them is divided
into six Parts, having several small Hairs issuing therefrom, and Ends with two Claws,
of unequal Lengths, very properly adapted to the particular Exigences of this Animal,
which has Occasion to walk either on Skin or Hair. For the lesser Claw a being so much
shorter than the other Claw b, when it walks on Skin the shorter Claw touches not, and
then the Feet are the same as those of a Mite and many other Insects : Whereas, when
amongst Hairs, the longer Claw can bend itself round by means of its small Joints, and
meeting with the shorter, can both together take hold and grasp a Hair, as with a Thumb
and Finger, after the manner represented in the Figure, where F F F, the Hair of a Man's
Head, is so grasped and held fast by this Creature, that it is in no danger of falling
The Belly is likewise very transparent, but its Covering bears the Resemblance of a Skin
rather than a Shell, being grained all over just like the Skin of a Man's Hand, and when
the Belly is empty, growing very slaccid and wrinkled.
H H shew the Stomach placed in the upper Part of the Belly.
The white Spot I I, may possibly be the Liver or Pancreas, which, by the peristaltic
Motion of the Guts, is moved a little to and fro, not with a Systole and Diastole, but ra-
ther with a thronging or justling Motion.
After one of these Creatures had fasted two Days, all the hinder Parts appeared lank
and wrinkled ; the white Substance I I, scarcely moved ; most of the white Branchings dis-
appeared, as did also the Redness or sucked Blood in the Guts, the peristaltic Motion
whereof was hardly to be discerned ; but upon suffering it to suck, the Skin of the Belly,
and the six scalloped Embossments on either side, were quickly filled out ; the Stomach
and Guts seemed quite crammed, and Multitudes of white Vessels appeared replete and
turgid ; the peristaltic Motion grew quick, and so did also the justling Motion of the Sub-
stance I I.
The Animal was so voracious, that notwithstanding it could contain no more, it con-
tinued sucking as greedily as ever, and at the same time emptied itself as fast behind.
And its Digestion must needs be very quick, for though the Blood, when sucked, appeared
thin and black, it soon became in the Guts of a lovely Ruby-colour, and that Part of it
which was carried into the Veins was evidently white : Whereby we also find, that a far-
ther Digestion of Blood may make it Milk, or at least of a milky Colour.
Near the Bottom of the Belly appears the Anus K, beset with Hairs or Bristles ; just
below are two little Parts L L, somewhat of a semicircular Figure, whose Insides are
covered with a Down, and which serve, occasionally, to cover and close the Aperture of
the Anus. At the Extremity of the Tail are a Couple of Bodies M M, resembling the
Rumps of Fowls, from whence issue a Number of sharp Hairs.
Dr. POWER takes notice, that having placed a Louse on its Back, in the Position here
before us, there were two bloody darkish Spots discernable ; the greater in the Midst of the
Body, and the lesser towards the Tail. In the Center of the larger Spot there is (says he)
a white Film or Bladder, which continually contracts and dilates itself upwards and down-
wards ; and always, after every Pulse of this white Particle or Vesicle, there follows a
Pulse of the great dark bloody Spot, in which, or over which this Vesicle seems to swim.
This he observed two or three Hours together, as long as the Louse lived ; for pricking the
white Vesicle with a small Needle, which let out a small Drop of Blood, and then viewing
it again with the Microscope, no Signs of Life or Motion could be perceived.
Lice proceed from Parents of their own Kind, and not (as formerly was supposed)
from certain Juices or Humours of human Bodies ; which may serve indeed to nourish,
but can never breed them. The Females lay Eggs, or Nits, which they fasten to the
Hairs of the Head, or to other hairy or woolly Substances, by a glewy Matter wherewith