In molluscs the external parts are as follows: in the first place,
the so-called feet; secondly, and attached to these, the head;
thirdly, the mantle-sac, containing the internal parts, and
incorrectly designated by some writers the head; and, fourthly, fins
round about the sac. (See diagram.) In all molluscs the head is found
to be between the feet and the belly. All molluscs are furnished with
eight feet, and in all cases these feet are severally furnished with
a double row of suckers, with the exception of one single species of
poulpe or octopus. The sepia, the small calamary and the large
calamary have an exceptional organ in a pair of long arms or
tentacles, having at their extremities a portion rendered rough by
the presence of two rows of suckers; and with these arms or tentacles
they apprehend their food and draw it into their mouths, and in
stormy weather they cling by them to a rock and sway about in the
rough water like ships lying at anchor. They swim by the aid of the
fins that they have about the sac. In all cases their feet are
furnished with suckers.

A third genus is that of the ostracoderms or 'testaceans'. These
are animals that have their hard substance outside and their
flesh-like substance within, and their hard substance can be shattered
but not crushed; and to this genus belong the snail and the oyster.

The fourth genus is that of insects; and this genus comprehends
numerous and dissimilar species. Insects are creatures that, as the
name implies, have nicks either on the belly or on the back, or on
both belly and back, and have no one part distinctly osseous and no
one part distinctly fleshy, but are throughout a something
intermediate between bone and flesh; that is to say, their body is
hard all through, inside and outside. Some insects are wingless,
such as the iulus and the centipede; some are winged, as the bee,
the cockchafer, and the wasp; and the same kind is in some cases
both winged and wingless, as the ant and the glow-worm.

Book IV

We have now treated, in regard to blooded animals of the parts
they have in common and of the parts peculiar to this genus or that,
and of the parts both composite and simple, whether without or within.
We now proceed to treat of animals devoid of blood. These animals
are divided into several genera.

One genus consists of so-called 'molluscs'; and by the term
'mollusc' we mean an animal that, being devoid of blood, has its
flesh-like substance outside, and any hard structure it may happen
to have, inside-in this respect resembling the red-blooded animals,
such as the genus of the cuttle-fish.

Another genus is that of the malacostraca. These are animals
that have their hard structure outside, and their soft or fleshlike
substance inside, and the hard substance belonging to them has to be
crushed rather than shattered; and to this genus belongs the
crawfish and the crab.

All sanguineous animals eject sperm. As to what, and how, it
contributes to generation, these questions will be discussed in
another treatise. Taking the size of his body into account, man
emits more sperm than any other animal. In hairy-coated animals the
sperm is sticky, but in other animals it is not so. It is white in all
cases, and Herodotus is under a misapprehension when he states that
the Aethiopians eject black sperm.

Sperm issues from the body white and consistent, if it be healthy,
and after quitting the body becomes thin and black. In frosty
weather it does not coagulate, but gets exceedingly thin and watery
both in colour and consistency; but it coagulates and thickens under
the influence of heat. If it be long in the womb before issuing out,
it comes more than usually thick; and sometimes it comes out dry and
compact. Sperm capable of impregnating or of fructification sinks in
water; sperm incapable Of producing that result dissolves away. But
there is no truth in what Ctesias has written about the sperm of the
elephant.

Milk remains

for a long time in the female, if she be kept from
the male and be properly fed, and, of quadrupeds, this is especially
true of the ewe; for the ewe can be milked for eight months. As a
general rule, ruminating animals give milk in abundance, and milk
fitted for cheese manufacture. In the neighbourhood of Torone cows run
dry for a few days before calving, and have milk all the rest of the
time. In women, milk of a livid colour is better than white for
nursing purposes; and swarthy women give healthier milk than fair
ones. Milk that is richest in cheese is the most nutritious, but
milk with a scanty supply of cheese is the more wholesome for
children.

Rennet then consists of milk with an admixture of fire, which
comes from the natural heat of the animal, as the milk is concocted.
All ruminating animals produce rennet, and, of ambidentals, the
hare. Rennet improves in quality the longer it is kept; and cow's
rennet, after being kept a good while, and also hare's rennet, is good
for diarrhoea, and the best of all rennet is that of the young deer.

In milk-producing animals the comparative amount of the yield
varies with the size of the animal and the diversities of pasturage.
For instance, there are in Phasis small cattle that in all cases
give a copious supply of milk, and the large cows in Epirus yield each
one daily some nine gallons of milk, and half of this from each pair
of teats, and the milker has to stand erect, stooping forward a
little, as otherwise, if he were seated, he would be unable to reach
up to the teats. But, with the exception of the ass, all the
quadrupeds in Epirus are of large size, and relatively, the cattle and
the dogs are the largest. Now large animals require abundant
pasture, and this country supplies just such pasturage, and also
supplies diverse pasture grounds to suit the diverse seasons of the
year. The cattle are particularly large, and likewise the sheep of the
so-called Pyrrhic breed, the name being given in honour of King
Pyrrhus.

...

In milk there is a fatty element, which in clotted milk gets to
resemble oil. Goat's milk is mixed with sheep's milk in Sicily, and
wherever sheep's milk is abundant. The best milk for clotting is not
only that where the cheese is most abundant, but that also where the
cheese is driest.

Now some animals produce not only enough milk to rear their young,
but a superfluous amount for general use, for cheese-making and for
storage. This is especially the case with the sheep and the goat,
and next in degree with the cow. Mare's milk, by the way, and milk
of the she-ass are mixed in with Phrygian cheese. And there is more
cheese in cow's milk than in goat's milk; for graziers tell us that
from nine gallons of goat's milk they can get nineteen cheeses at an
obol apiece, and from the same amount of cow's milk, thirty. Other
animals give only enough of milk to rear their young withal, and no
superfluous amount and none fitted for cheese-making, as is the case
with all animals that have more than two breasts or dugs; for with
none of such animals is milk produced in superabundance or used for
the manufacture of cheese.

The juice of the fig and rennet are employed to curdle milk. The
fig-juice is first squeezed out into wool; the wool is then washed and
rinsed, and the rinsing put into a little milk, and if this be mixed
with other milk it curdles Rennet is a kind of milk, for it is found
in the stomach of the animal while it is yet suckling.

The people that live on and about Mount Oeta take such she-goats
as decline the male and rub their udders hard with nettles to cause an
irritation amounting to pain; hereupon they milk the animals,
procuring at first a liquid resembling blood, then a liquid mixed with
purulent matter, and eventually milk, as freely as from females
submitting to the male.

As a general rule, milk is not found in the male of man or of
any other animal, though from time to time it has been found in a
male; for instance, once in Lemnos a he-goat was milked by its dugs
(for it has, by the way, two dugs close to the penis), and was
milked to such effect that cheese was made of the produce, and the
same phenomenon was repeated in a male of its own begetting. Such
occurrences, however, are regarded as supernatural and fraught with
omen as to futurity, and in point of fact when the Lemnian owner of
the animal inquired of the oracle, the god informed him that the
portent foreshadowed the acquisition of a fortune. With some men,
after puberty, milk can be produced by squeezing the breasts; cases
have been known where on their being subjected to a prolonged
milking process a considerable quantity of milk has been educed.

All milk is composed of a watery serum called 'whey', and a
consistent substance called curd (or cheese); and the thicker the
milk, the more abundant the curd. The milk, then, of non-ambidentals
coagulates, and that is why cheese is made of the milk of such animals
under domestication; but the milk of ambidentals does not coagulate,
nor their fat either, and the milk is thin and sweet. Now the
camel's milk is the thinnest, and that of the human species next after
it, and that of the ass next again, but cow's milk is the thickest.
Milk does not coagulate under the influence of cold, but rather runs
to whey; but under the influence of heat it coagulates and thickens.
As a general rule milk only comes to animals in pregnancy. When the
animal is pregnant milk is found, but for a while it is unfit for use,
and then after an interval of usefulness it becomes unfit for use
again. In the case of female animals not pregnant a small quantity
of milk has been procured by the employment of special food, and cases
have been actually known where women advanced in years on being
submitted to the process of milking have produced milk, and in some
cases have produced it in sufficient quantities to enable them to
suckle an infant.

These liquids, then, are nearly always congenital in animals,
but milk and sperm come at a later time. Of these latter, that
which, whensoever it is present, is secreted in all cases
ready-made, is the milk; sperm, on the other hand, is not secreted out
in all cases, but in some only, as in the case of what are
designated thori in fishes.

Whatever animals have milk, have it in their breasts. All
animals have breasts that are internally and externally viviparous, as
for instance all animals that have hair, as man and the horse; and the
cetaceans, as the dolphin, the porpoise, and the whale-for these
animals have breasts and are supplied with milk. Animals that are
oviparous or only externally viviparous have neither breasts nor milk,
as the fish and the bird.

We now proceed to discuss the properties of marrow; for this is
one of the liquids found in certain sanguineous animals. All the
natural liquids of the body are contained in vessels: as blood in
veins, marrow in bones other moistures in membranous structures of the
skin

In young animals the marrow is exceedingly sanguineous, but, as
animals grow old, it becomes fatty in animals supplied with fat, and
suet-like in animals with suet. All bones, however, are not supplied
with marrow, but only the hollow ones, and not all of these. For of
the bones in the lion some contain no marrow at all, and some are only
scantily supplied therewith; and that accounts, as was previously
observed, for the statement made by certain writers that the lion is
marrowless. In the bones of pigs it is found in small quantities;
and in the bones of certain animals of this species it is not found at
all.

Women are seldom afflicted with varicose veins, with haemorrhoids,
or with bleeding at the nose, and, if any of these maladies supervene,
the menses are imperfectly discharged.

Blood differs in quantity and appearance according to age; in very
young animals it resembles ichor and is abundant, in the old it is
thick and black and scarce, and in middle-aged animals its qualities
are intermediate. In old animals the blood coagulates rapidly, even
blood at the surface of the body; but this is not the case with
young animals. Ichor is, in fact, nothing else but unconcocted
blood: either blood that has not yet been concocted, or that has
become fluid again.

Blood in the female differs from that in the male, for,
supposing the male and female to be on a par as regards age and
general health, the blood in the female is thicker and blacker than in
the male; and with the female there is a comparative superabundance of
it in the interior. Of all female animals the female in man is the
most richly supplied with blood, and of all female animals the
menstruous discharges are the most copious in woman. The blood of
these discharges under disease turns into flux. Apart from the
menstrual discharges, the female in the human species is less
subject to diseases of the blood than the male.

If blood be
removed or if it escape in any considerable quantity, animals fall
into a faint or swoon; if it be removed or if it escape in an
exceedingly large quantity they die. If the blood get exceedingly
liquid, animals fall sick; for the blood then turns into something
like ichor, or a liquid so thin that it at times has been known to
exude through the pores like sweat. In some cases blood, when
issuing from the veins, does not coagulate at all, or only here and
there. Whilst animals are sleeping the blood is less abundantly
supplied near the exterior surfaces, so that, if the sleeping creature
be pricked with a pin, the blood does not issue as copiously as it
would if the creature were awake. Blood is developed out of ichor by
coction, and fat in like manner out of blood. If the blood get
diseased, haemorrhoids may ensue in the nostril or at the anus, or the
veins may become varicose. Blood, if it corrupt in the body, has a
tendency to turn into pus, and pus may turn into a solid concretion.

A fat substance is incorruptible, but blood and all things
containing it corrupt rapidly, and this property characterizes
especially all parts connected with the bones. Blood is finest and
purest in man; and thickest and blackest in the bull and the ass, of
all vivipara. In the lower and the higher parts of the body blood is
thicker and blacker than in the central parts.

Blood beats or palpitates in the veins of all animals alike all
over their bodies, and blood is the only liquid that permeates the
entire frames of living animals, without exception and at all times,
as long as life lasts. Blood is developed first of all in the heart of
animals before the body is differentiated as a whole.

Animals that are internally and externally viviparous are more
abundantly supplied with blood than the sanguineous ovipara. Animals
that are in good condition, either from natural causes or from their
health having been attended to, have the blood neither too abundant-as
creatures just after drinking have the liquid inside them in
abundance-nor again very scanty, as is the case with animals when
exceedingly fat. For animals in this condition have pure blood, but
very little of it, and the fatter an animal gets the less becomes
its supply of blood; for whatsoever is fat is destitute of blood.

And now to proceed to the consideration of the blood. In
sanguineous animals blood is the most universal and the most
indispensable part; and it is not an acquired or adventitious part,
but it is a consubstantial part of all animals that are not corrupt or
moribund. All blood is contained in a vascular system, to wit, the
veins, and is found nowhere else, excepting in the heart. Blood is not
sensitive to touch in any animal, any more than the excretions of
the stomach; and the case is similar with the brain and the marrow.
When flesh is lacerated, blood exudes, if the animal be alive and
unless the flesh be gangrened. Blood in a healthy condition is
naturally sweet to the taste, and red in colour, blood that
deteriorates from natural decay or from disease more or less black.
Blood at its best, before it undergoes deterioration from either
natural decay or from disease, is neither very thick nor very thin. In
the living animal it is always liquid and warm, but, on issuing from
the body, it coagulates in all cases except in the case of the deer,
the roe, and the like animals; for, as a general rule, blood
coagulates unless the fibres be extracted. Bull's blood is the
quickest to coagulate.