ON

TAPE AND CYSTIC WOMS,

WITH AN INTEODUCTION

ON. THE

ORIGIN OF INTESTINAL WOMS.

BY

CARL THEODOR VON SIEBOLD,

PKOFBSSOR IN THE UNIVBRSITT 01? MtTlTICH.

TRANSLATED BY

T. H. HUXLEY, F.R.S.,

WITH TllIRTY-SIX WOODCUTS.

LONDON:
ntlNTED roil THE SYDENHAM SOCIETY.

MDCCCLVU.

PRINTED IIY J. E, ADLARD, HARTHOl.OMEW CLOSE.

VON SIEBOLD

ON

TAPE AND CYSTIC WOUMS.

CONTENTS.

PAGE

Author's Preface • • • • • * ^

3

Introduction . . • • • • • '

CHAPTER 1.

Origin of Intestinal Worms . • - • • .3

CHAPTER II.

On the Tape-worm . . • ■ • . . 31

Encysted Cestoidea . • • • • . 3o

The Scolex state . . • ■ • . . 35

Development of Scolices . . • • • .37

Proglottides . - • • • • . . 41

CHAPTER III.

Cystic Entozoa . . . • • • .47

CHAPTER IV.

On the origin of the Cestoid and Cystic Entozoa . . . 57

1. Experiments on feeding with Cys/icercMsjsisi/brjMM . . .59

2. Experiments on feeding with Cysdcercus tenuicollis . . . 62

3. Experiments on feeding with Cysticercus cellulosce . . .66

4. Experiments on feeding with Ccenurus cerebralis . . . . 69

5. Experiments on feeding with Echinococcus Veterinorum . . .73

6. On diseases produced by Cystic worms and their prevention . . 77
Cysticerci in sausages . . . . .85
Cestoid epidemic of Iceland . . . . . . 87

AUTHOR'S PEEEACE.

Investigations into the natural history of the entozoa^ con-
tinued for many years, have taught me that it is impossible to
obtain a complete view of the different stages of existence through
which these parasites pass, if one's observations are restricted to
but a few of the localities in which they are found. At an early
period of my researches, it became evident that the same entozooh,
in its young state, may have a very different habitation from that
in which it is found in its adult condition; for these animals
undergo the most remarkable metamorphoses, and their habits
varying with their changes in form and age, they are necessitated
repeatedly to change their residence.

These peculiarities in the natural history of the entozoa, often
most difficult of investigation, have rendered the task of the
helminthologist, in seeking to obtain a just conception of their
genera and species, a very difficult one. It has only too fi^equently
happened that the different stages of development of the same
species of entozoa, have been described as so many distinct species
or genera ; and thus the systematic arrangement of the group has
been built upon a faulty foundation. Hence, again, a difficulty
has arisen in the way of attaining correct ideas with regard to the
modes of propagation of the intestinal worms, and this obstacle
could only be removed by determining, in defiance of the authority
of the older helminthologists, to give up many genera and species
established upon what they supposed to be independent forms.

1

2

AUTHOR'S PREFACE.

The investigation of the natural history of the intestinal worms,
at the same time, opened up a channel through which their mode of
origin could be traced ; and indicated a way in which the attacks
of those parasites which are dangerous or troublesome to man
and animals, could be prevented; an object, in certain cases, of
the highest importance, since the morbid changes induced by
many entozoa in the organs which they infest, are not always
removable.

For a long period, I have been at much pains to inquire into
the origin of the entozoa found in man and the domestic animals ;
and in the present essay I lay before physicians, veterinarians,
and breeders, a summary of the results of the observations
and experiments which I have made upon the production and
development of these creatures. My chief attention has been
directed to the destructive cystic-worms, and I believe that the
conclusions at which I have arrived are not merely a gain for
science, but promise to be of useful practical application.

Munich ; March 30M, 1854.

INTRODUCTION.

CHAPTER I.

UPON THE ORIGIN OF INTESTINAL WORMS.

Having been occupied for many years with inquiries into the
natural history of the intestinal worms, a subject involved in
much obscurity, I have gradually arrived at the decided conclusion
that these parasites do not originate, as has been commonly
believed, by "equivocal generation," from substances of a dis-
similar nature. With the usual exaggeration and misuse of
language, the doctrine of equivocal generation has been applied
both to the infusoria and to the intestinal worms. It was diffi-
cult, at first sight, to account for the origin and reproduction of
these animals, and, even upon closer investigation, they presented
many phenomena which could not be recognised in the organiza-
tion and vital manifestations of other, especially of the higher
animals ; but instead of seeking for the cause of these exceptional
peculiarities, people, accommodating themselves to the usually
accepted view as to the natural history of these lower creatures, set
the matter straight in their minds, by supposing that the unusual
phenomena occurred somehow or other in that way ; thus allowing
the imagination to indulge in fancies of the wildest description, and
even in opposition to the most important laws of nature. It was
in this manner that physicians and naturalists thought themselves
justified in assuming, that the parasitic worms in the intestines
of men and animals owed their origin to ill-digested nutriment,
or that they were developed in the most widely different organs
from corrupt juices. They took it for granted, that certain

4

INTRODUCTION.

morbid processes in any organ were competent to give rise to para-
sites, assuming that the elementary constituents of an organ affected
by disease, mechanically separated themselves from their natural
connection, and not perishing, but transforming themselves into
independent organisms, became parasites. Clothed in fine phrases,
this idea was everywhere received with favour, and took such deep
hold of the public mind, that it is now 'a matter of no small
trouble to eradicate what has, with many, become an article of
faith, and to substitute the laws of nature, drawn from experience,
for the creation of their fancy. It was certainly more convenient
and enticing to give free scope to one's thoughts, and to fill up
the frequent gaps left in our knowledge of the origin and multipli-
cation of the lower animals, with pure hypotheses, than as now,
renouncing this faulty method of inquiry into nature, to attain,
by troublesome researches and careful experiments, a secure insight
into her hidden workings.

It was by the latter method that a remarkable and hitherto
unanticipated development of the sexual apparatus was discovered
in many parasites, such as round-worms, thread-worms, tape-
worms, and flukes,^ in which such an immense mass of eggs
and young can be generated, that it seems unnecessary to look
further in order to account for their origin. But the precise
mode in which the countless brood of these parasites make their
way into the interior of the animals they are destined to inhabit,
was long but dimly understood, until by degrees attention was
directed to certain peculiarities in the mode of life of these
creatures, which threw great light upon the subject.

It has been ascertained, in fact, that at particular periods of their
existence, the intestinal worms undertake emigi'ations, and these
often very extensive ones, in order to reach that animal whose
organs are by nature fitted for their habitation. We now know
that the young of the tape-worm, (which inhabits the intestine of
the higher animals only,) leave the place where they were brought

> With respect to the tape-worms, it is well known that a single individual is often com-
posed of many hundred joints. Each joint is capable of laying many hundred ova, so
that tlie number of the progeny of a single tape-worm is enormous. Professor Eschricht
of Copenhagen (see his work ' Das Physische Leben iii populiiren Vortriigen, Berlin,
1852, p. 115) posesses a tape-worm, expelled by a patient of his, which consists of
1000 joints, and some of the joints contain more than 1000 ova. The same miter
(ibid., p. 112) having carefully examined the reproductive organs of a female ^*eam
Ivmbricoides, estimates the number of eggs in a single thread-worm at many millions.

OEIGIN OF INTESTINAL WOEMS.

5

forth/ or laid as eggs (that is to say, they emerge from the intes-
tine of their parent's host), and seek an opportunity to enter into
the intestine of some other creature. It is easy to convince
oneself of this emigration of the young of the tape-worm, by
examining the excrement of animals infested by them, at those
times of the year at which they attain their sexual maturity.
We then observe, that sometimes single joints, or connected
series of joints, full of ova ; sometimes immense masses of the
ova, are passed with the faeces. The same thing holds good
•with regard to the ova of the Distomata that infest the livers of
our ruminating animals ; their eggs, after they have been trans-
ferred from the liver to the gall-ducts, being washed out with the
bile into the intestine, and evacuated with the dung.

These emigrations of the young of the intestinal worms benefit
not only the creatures they infest, but themselves. There are many
kinds of intestinal worms, in whose eggs the embryo is never hatched
if they remain in the place where they have been laid. They
must wander to some other place in order to develop their young,
or to allow of the escape of the young already developed in them.^
These young must then either wait for, or seek, an animal to
lodge in, having entered into which, they are capable of attaining
sexual maturity. By such emigrations the infested animals are at
the same time freed from guests, whose increase would be both
troublesome and prejudicial. For example, what would happen
if the millions of eggs that a single round-worm or tape-worm
can produce, were to develop and generate their young in the
same intestine in which they were laid ? Would not the intes-
tine, after the young had attained their full growth, and brought
forth others in their turn, become at last so choked up as to
disable this part of the digestive apparatus, so that the whole
organism of the unhappy animal must perish, together with his
parasites ? In any case, the emigration and immigration of the
young of the intestinal worms, is a very important though long
Tinregarded part of the history of their propagation; and since

' Hence a tape-worra ^vhich has found its way into the intestine of an appropriate
animal will attain its sexual maturity, but will not, properly speaking, multiply its kind
there. Forthis reason, the tape-worm {Tania solium) infesting the human subject,
which 13 common in Germany, France, [and England,] is commonly called the
solitary worm, (Einsiedler-wurm, ver solitaire,) although the name is not a very fit one
as It depends entirely on accident nhether only a single individual or a whole society of
these worms shall enter the human intestine in the course of their wanderings

& INTRODUCTION.

physicians and naturalists have devoted the requisite attention to
the subject of these wanderings (to which I directed attention
some years back^), a number of facts have been discovered, show-
ing more and more that the origin of the intestinal worms in the
viscera of animals can be readily accounted for according to
natural laws; whereas formerly, hardly anything being really
known of the natural history of these parasites, their mode of
origin and propagation, already difficult enough of comprehension, ^
was rendered more and more mysterious by an hypothesis of
" equivocal generation" entirely devoid of any direct support.

An important circumstance, very favorable to the progeny
of the intestinal worms during their wanderings, is the solidity
of the egg-shell in which they are commonly contained. By
its hardness and resistance, the egg-shell of many kinds of
intestinal worms efficiently protects the enclosed germ and
yelk, or the already developed embryo, against injury from
without, and maintains within the ovum the degree of moisture
requisite for the further development of the young. In this
way the ova preserve their vitality for months together, not-
withstanding the many vicissitudes to which they are exposed
after lea^dng the dwelling of their parents. They pass into
dust-heaps, pri^des, drains, &c., where, surrounded sometimes by
a greater, sometimes by a lesser degree of moisture, they are
subjected to various degrees of temperature, until, deposited
in the diuig-heaps into which corrupt and mouldering organic
'substances are usually converted, they are, as manure, spread
upon the fields and meadows, where, under favorable in-
fluences of the weather, particularly if supplied with adequate
moisture, they become further developed. It will be obvious that
the young of the intestinal worms have not far to seek for an
opportunity of re-entering other animals, when we consider that
they are scattered through the manured soil amongst the seeds
that have been sown there; that these produce plants which
generally serve for the support of men and animals, and that the
young worms adhering to them may thus be easily swallowed.
Again, it may well happen that showers of rain occasionally
wash out the ova of the intestinal worms from the dung-heaps
or manured soil, carrying them off into streams and brooks, and

. See my article " Parasiten" in R. Wagner's ' HandwOrterbucli dor Physiologic,'
Bd. ii, 1844, p. 645.

OEIGIN OF INTESTINAL WOKMS.

7

so affording another mode of entrance into men and animals,
by the water which the latter drink.

Many of the young intestinal worms, more or less developed,
but still enclosed in the egg-shell, remain quite inactive in their
wanderings, and for these passive emigrants it is, of course, a
mere matter of chance whether they reach their goal or not.
The young of others, having previously left their egg-shell, may
take an active share in the process, creeping up out of their holes
and corners in wet weather, or in the damp mornings, upon the
slippery plants, and so entering the animals fitted for their habita-
tion, when they come to seek for food.

According to an old- standing custom which careful shepherds
strictly keep up, sheep are never allowed to be driven out in the
morning till all the dew is off the grass, nor yet to graze in damp
swampy pastures. By this precaution the shepherds unwittingly
protect their charges from the attacks of Strongyli and Distomata.
It is on like grounds that seasons of wet weather are so frequently
fatal to flocks, it being then easier for the young intestinal worms
to enter the sheep and give rise to entozoic pestilence; whilst
in continuously dry and hot seasons a great number of these
young worms must be dried up and destroyed, and thus the sheep
are delivered from their attack and all its evil consequences.

But in thus expressing my opposition to the various hypotheses
of the origin and multiplication of the parasitic worms, it might
appear as if I had fallen into the very error I condemn, and the
objection might be raised that the explanation I have just given
of the singularities observed in the mode of occurrence of the
intestinal worms is, like former hypotheses, merely imaginary,
and that I am unable to support it by demonstrative experimental
evidence.

This I must beg leave to deny. It is true that what I have
said respecting the origin of the Strongylus filaria and of the
flulce {Distomum hepaticum) in sheep, is as yet only an assumption,
and not to be regarded as directly proven. Nevertheless, my
assumption rests upon the analogy of reliable facts, which I have
established by observation in other intestinal worms. The
recognition of definite, though at first isolated truths, has often
done much for science, since by careful application of the laws
of analogy they have furnished the key to phenomena long hidden
in obscurity.

In order to show that emigration and immigration are regular

8

INTRODUCTION

phases in the life of many intestinal worms, I Avill here recaU
certain observations of my own on the natural history of the
following parasites.

For a long time the origin of the thread-worm, known as
Filaria Insectorum, that lives in the cavity of the bodies of adult
and larval insects could not be accounted for. Shut up within
the abdominal cavity of caterpillars, grasshoppers, beetles, and
other insects, these parasites were supposed to originate by
equivocal generation, under the influence of wet weather or from
decayed food. Helminthologists were obliged to content them-
selves with this explanation, since they were unable to find a
better. Those who dissected these thread- worms and submitted
them to a careful inspection, could not deny the probability of the
view that they arose by equivocal generation, since it was
clear that they contained no trace of sexual organs. Eut on
directing my attention to these entozoa, I became aware of the
fact that they were not true Filaria at all, but belonged to a
peculiar family of thread-worms, embracing the genera Gordius
and Mermis. Furthermore, I convinced myself that these parasites
wander away when fdl grown, boring their way from within
through any soft place in the body of their host, and creeping out
through the opening. How many a butterfly-collector, keep-
ing caterpillars for the breeding of fine specimens of butter-
flies, must have seen one or more yellowish white thread- worms
winding their way out of them ! These parasites do not emigrate
because they are uneasy, or because the caterpillar is sickly, but
from that same internal necessity which constrains the horse-fly
to leave the stomach and intestine of the horse where he has been
reared, or which moves the larva of the gad-fly to work its way
out of the boils on the skin of oxen. The larvae of both these
insects creep forth in order to become chrysalises and thence to
proceed to their higher and sexual condition. This desire to
emigrate is implanted in very many parasitic insect larvse, and has
long been a well-known fact in entomology. Now I have demon-
strated, that the perfect, full-grown, but sexless thread-worms of
insects are, in like manner, moved by this desire to wander out of
their previous homes in order to enter upon a new period in their
lives which ends in the development of their sexual organs. It is
true that in the boxes and other receptacles, in which one
is generally accustomed to keep caterpillars, these creatures
perish ; they roll themselves together, and from the absence of

OEIGIN OP INTESTINAL WORMS.

9

the necessary moisture, they in a short time dry up. But their
fate is very different when the infested insects remain under
natural conditions ; the thread- worms, as they leave the bodies of
their hosts, then fall to the ground, and crawl away into the deeper
and moister parts of the soil. Thread-worms found in the damp
earth, in digging up garden-beds and cutting ditches in the fields,
have often been brought to me, which presented no external
distinctions from the thread-worms of insects externally. This
suggested to me that the wandering thread-worms of insects
might be instinctively necessitated to bury themselves in damp
ground, and I therefore instituted a series of experiments with
such entozoa (which I procured in numbers from the caterpillars
of a moth, Yponomeuta evonymella), by placing the newly emigrated
worms in flower-pots filled with damp earth.^ To my delight, I
soon perceived that these worms^ began to bore with their heads
into the earth, and by degrees drew themselves entirely in. For
many months (through the whole winter) I kept the earth in the
flower-pots moderately moist, and on examining the worms from
time to time I found, to my great astonishment, that the sexual
apparatus became gradually developed in them, and that, after a
time, eggs were formed and were eventually deposited by hundreds
in the earth. Towards the conclusion of winter I could succeed
in detecting the commencing development of the embryo in these
eggs. By the end of spring they were fully formed, and many of
them, having by this time left their shells, were to be seen creeping
about the earth in the flower-pots, which I still carefully kept
damp, I now conjectured that these young worms would be
impelled by their instincts to pursue a parasitic existence and to
seek out an animal to inhabit and grow to maturity in, and it
seemed not improbable that the brood I had reared would, like
their parents, thrive best in the caterpillar. In order, therefore,
to induce my young brood to immigrate, I procured a number of
very small caterpillars of Yponomeuta, of half a line in length,
which the first spring sunshine had just called into life. For
the purpose of my experiment I filled a watch-glass with damp
earth, taking it from amongst the flower-pots where the thread-
worms had wintered, and of course satisfying myself that it con-

' These experiments and their results have been already published in the ' Entomo-
logische Zeitung,' 1848, p. 290.

=" I have named this species of thread-worm Mermis albicans.

10

INTRODUCTION.

tained a number of lively young of the Mtrmis albicans. Upon
this I placed several of the young caterpillars of the Yponomeuta in
order that the worms might gratify their immigrative propensities.
I must explicitly remark, that before experimenting with the
caterpillars, I carefully examined each with the microscope, in order
to ascertain whether it was not already inhabited by young thread-
worms. From their softness and transparency^ I could ascertain
this point with certainty, without in the least injuring them.
The event proved that this inspection was necessary, for out of
twenty-five individuals which I at first selected, three contained a
thread- worm embryo, which was excessively like those in the
flower-pots. I published the results of these experiments a year
or two back, in an essay upon the thread-worms of insects^, from
which I quote the following :

" From amongst those caterpillars which microscopic inspection
clearly demonstrated to be free from thread-worms, thirteen were
placed in a watch-glass filled with damp earth containing many
lively Mermis-emhrjo^. After eighteen hours I was able to
discover Mermis-emhrjo^ in five of the caterpillars. On a second
occasion, three-and-thirty of the caterpillars of Yponomeuta
cognatella, likewise carefully examined and found free from
parasites, were in the same way placed in a watch-glass filled
with damp earth containing Memis-embryos. After four-and-
twenty hours, fourteen contained ilfermi^-embryos. Six of these
little caterpillars each contained two small worms, whilst in two
others there were as many as three worms. I also employed
other caterpillars (of three lines in length) of Pontia Crataegi,
Lijmris chrysorrJma, and Gastropacha Neustria, which I took out
of coccobns where they had passed the winter. They were, in
like manner, placed in a watch-glass upon moist earth containing
JMermis-emhxjos. On the next day, among fourteen caterpillars
thus treated, I found ten infested with ikfermw-embryos ; five of
these contained two worms each, and into one even three worms
had wandered.^' It was clear that these young thread-worms
had bored their way through the soft skin into the interior of the
young caterpillars.

Prom the results of the experiments I have just recorded,
one must conclude that it is not necessary to turn to the
mystical doctrine of equivocal generation for an explanation

' See 'Entoraolngische Zeitung,' 1850, p. 239.

OEiaiN 0$" INTESTINAL WOKMS.

11

of the presence of worms in insects, since here the origin of
the parasites is sufficiently obvious. Those who cannot make up
their minds to renounce the easy and convenient doctrine of
equivocal generation, may perhaps object, that the history I
have given of the propagation of the Mermis albicans stands
alone, and only makes an exception from the rule. To this I
answer, in the words of Goethe : " Nature goes her way, and that
which appears to us as the exception, is the rule." That this is
really the case in the present instance, is proved by recent
investigations into the natural history of the intestinal worms.
Since attention has been directed to their wanderings, more and
more facts have been daily brought to light, all tending to
show that the emigration and immigration of these parasites is a
much commoner and more widely extended occurrence than was
at first imagined. Habits, very similar to those which I have
just described in Mermis albicans, are also to be observed in
another thread-worm, the well-known Gordius aquaticus, which
has also been shown to live parasitically in the cavities of the
bodies of various insects, viz. : grasshoppers, terrestrial and
aquatic beetles, and in their larvae ; and to grow from a most
diminutive worm to one of several inches in length, which then
makes its way out, to attain to sexual matui'ity elsewhere, often
in the water. These facts were formerly wholly unknown, though
it must have long appeared surprising that this thread-worm,
which, on account of its form and colour has been compared
to a horse-hair, is, whenever met with in the water, of its full
size. But now that we know that the Gordius aquaticus, like
the Mermis albicans, enters in the embryo state into insects,
growing with them, and only quitting them when it has done
growing, the striking phenomenon I have mentioned is easily
accounted for.

Just as, for the reasons abeady named, some kinds of para-
sites that have emigrated are never met with below a certain
size; so, some kinds of parasites that have abeady made
their way into the interior of animals are not to be found
imder a certain size, however often and carefully they may be
sought for, a circumstance which must certainly have been
noticed by many physicians and natm-alists, without their having
paid further attention to it. It is now known that many para-
sites do not enter into the animals in which they are to pass
through their further stages of growth until they have attained a

12

INTRODUCTION.

certain degree of development elsewhere. This is particularly
the case with such intestinal worms as remain parasitic in the
last stage of their existence^ viz. — that of sexual maturity, whilst
the Gordiaccei [Gordius and Mermis), as soon as they are full-
grown, quit their parasitical life, in order to become sexually
mature, away from the animal they have infested. During these
early wanderings, the worms in question commonly undergo a
change of form — ^a sort of metamorphosis, often accompanied by
other phenomena of so highly remarkable and abnormal a
character, that naturalists could not at first understand the varied
character and import of these phases of existence, nor comprehend
their relation with hitherto known facts. ^ For a long time it
was supposed that these discoveries were isolated facts, and they
were regarded as a sort of curiosity; but here again the saying
was verified, that that which at first appeared to be the exception,
eventually proves to be the rule. By degrees, a mass of obser-
vations upon certain remarkable metamorphoses of the intestinal
worms accumulated, and constituted a complete chaos of seem-
ingly irregular phenomena, which broke down every barrier
hitherto set by the acknowledged laws of animal existence
and propagation, until the penetration of the Danish naturalist,
Steenstrup,^ succeeded in evolving a certain order out of this
confusion, by the discovery therein of a hidden, underlying law
of nature, by which all the phenomena that had seemed so devoid
of plan could be reduced to order. Steenstrup named the newly
discovered law, the " Alternation of Generations,'' a phrase which
describes this phenomenon. " That an animal bears young which

' I may refer to the " king's-yellow" worms discovered by Bojanus in water-snails,
and now become famous. (See Oken's ' Isis,' 1818, p. 729, plate 9, figs, a, t.) Of this
discovery Oken says " Observations of this kind make one dizzy." No less attention
was excited by Von Bar's description of the Bucephalus polymorphus of the fresh-water
mussel. (See ' Verhandlungen der Kaiserl. Akad. d. Naturforscher,' B. xiii, 1826,
p. 570, pi. 30) ; and by the Leucochloridum paradoxum, &r&t discovered by Ahrens, and
afterwards described anew by Carus. (See ' Magazin der Naturforschenden Frennde zu
Berlin, 1810, p. 292, pi. 10, figs. 12— 19, and the < Verhandlungen der Kaiserlicheu
Akademie,' Bd. xvii, 1855, p. 87, pi. 7.)

s See his important essay on the ' Alternation of Generations,' Copenhagen, 1842,
[This essay has been translated by Mr. Busk, and forms one of the publications of the
Kay Society. It must not be forgotten that the first conception of the doctrine of the

Alternation of Generations," and the first use of the term, are due to Chamisso. See his
'De Animalibus quibusdam e classc vermium Linnaana,' 1819, and ' Reise urn die
Erde.'— Ed.]

OEIGIN OF INTESTINAL WOEMS.

13

are, and remain, dissimilar to their parent, but bring forth a new
generation, whose members either themselves, or in their descend-
ants, return to the original form of the parent animal/'

Any one who has not familiarized himself with the fun-
damental idea of this doctrine of the alternation of generations,
may easily imagine it to be nothing but a modification of the
long well-known metamorphosis, exemplified by the tadpoles of
frogs and toads, or by the larvse and chrysalises of most insects.
This is, however, by no means the case. Those reptiles and
insects that are subject to metamorphosis, no doubt bring forth
young that diff'er from the parent, but there are two respects in
which the act of simple metamorphosis widely difi'ers from the
highly complex alternation of generations.

Although Steenstrup has already particularly noticed these
two grounds of difierence in his definition of the alternation of
generations, I deem it not altogether superfluous on my part
once more to draw especial attention to these important diver-
gences, if only for the benefit of those who are unfamiliar with
the phenomena. The first point of difierence between the
alternation of generations, and metamorphosis, is, that the young
of those animals whose mode of development comes under the
former head, are not only unlike their parent at first, but remain
so : the second distinction rests on the important fact that this
yoimg generation, so dissimilar to the parent animal, brings
forth new creatures, which either themselves, or in their descend-
ants, revert to the original form of the first parent. Whereas,
on the other hand, in simple metamorphosis, the dissimilar
young pass by gradual changes into the likeness of the parent
animal, and until this metamorphosis is complete, are incapable of
generation. Steenstrup has given the name of " nurse" to those
young, which, whilst departing from the parent type, remain, and
propagate under their own form.

It thus happens that in the alternation of generations (to use
the words of Steenstrup), the parent animal produces " nurses,"
whose descendants only, take her form. A most important
circumstance which characterises these nurses or " Agamozooids"-^

' I have rendered the word " keim-korper" by " sporula," meaning thereby a free
germ which is capable of development without fecundation, just as is the spore of a
cryptogamous plant. When the sporula; are developed in a special organ I term this
organ (the " keimstock" of Von Siebold) the " sporularium." Any independent form
from which sporulse or their equivalents alone are developed (the " ammen" or " nurses"
of Von Siebold, Steenstrup, &c.) I terra " agamozooids," See concluding note.— [Ed.]

INTRODUCTION.

pliysiologically, is, that they bring forth young, without themselves
possessing any real sexual apparatus. These Agamozooids, in
tact, multiply by division, by external or internal gemmation ;
they develop within their bodies germs which become fresh
creatures. But these germs do not deserve the title of " eggs
nor is the place where they are developed to be called an
"ovarium," since the germs, which I shall for the future
distinguish by the name of " sporulffi," are not only devoid
of the ordinary constituents of an ovum, as vitelline mem-
brane, yolk, germinal vesicle, and so called germinal spot,
but the further development of the germ-body is not pre-
ceded by those conditions, (I mean that "impregnation" by
means of a special seminal matter produced in a testis,) which
is essential to the development of true ova developed within
an ovarium. The organ in which, in certain Agamozooids the
"gemmae" are formed, cannot therefore be properly termed an
■" ovarium," and I shall distinguish it by the name of " sporula-
rium." No " nurses" present any sexual distinctions, and hence
their method of multiplication and propagation, which takes place
by means of sporulse formed within sporularia, or by ordinary
budding, or by division, must be an-anged amidst the modes of
asexual reproduction.

Very many cases of the alternation of generations occur
among the Ti^ematoda. The relations that the various changing
forms of these animals have to one another, remained long un-
suspected, since it was not an easy matter to discover among the
various successively alternating generations of a single fluke-
worm, the clue to their origin from one and the same parent.
The recognition of the connection of these forms, was ren-
dered more difficult of discovery by the fact, that these alternating
generations of animals not only changed their appearance, but
also their dwellings, whereby their parentage was still further
concealed. These multitudinous difficulties in the way of the
observers of the alternation of generations, render it impossible
for me to give a complete account of all the complex series of
changes undergone by any single Trematode in the course of its
development. Up to this time only longer or shorter fragments
of the circle of vital phenomena, broken as they are into many
phases by the alternation of generations, have been made out in a
few Trematoda.

However, these fi-agments do not relate to one and the same
period in the life of these parasites, nor to the same generations

OEIGIN OF INTESTINAL WORMS.

15

c f Agaraozooids, but to the most widely various periods and stages
of their deA^elopment. We can, therefore, by careful selection and
judicious arrangement of these observations, build up a general
view of the complicated process of the alternation of generations
in the Trematoda in general.

The so-called Cercaria offer the best exemplification of the
alternation of generations as it occm's in the Trematoda. These
Cercarioi, which swim about with great activity by means
of a cylindrical tail, have long been known; but until the
discovery of their real origin and signification, were taken, on
account of their diminutiveness, for Infusoria. When, at a
recent period, their parasitic nature was recognised, it became a
matter of much astonishment that the Cercarice were not
derived from parents resembling themselves, but that they
originated in peculiar animated, worm-shaped sacs, which were
found buried amidst the sexual and digestive organs, in various
kinds of fresh- water snails and
mussels. The form of the sacs
that produce the Cercarice is, not-
withstanding the simplicity of their
organization, very various; in ac-
cordance with the form and kind
of Cercaria to be developed within
them. Some kinds of Cercan«-sacs
have an oral aperture, and a simple
blind intestine, but in others this di-
gestive apparatus is entirely want-
ing. One series of Cercaria-sa.cs
whilst others again are stiff and

cular group, the Cercaria-sacs are simple shut receptacles; in
another, the sacs ramify and anastomose to a great extent. The
whole of these multifariously-shaped Cercaria-sacs enclose within
the walls of their bodies a cavity which, besides the intestinal

Fig. 1.

possesses contractile walls,
inflexible. In one parti-

Fig. 1. A cercaria-sac (two lines long) provided with an elongated alimentary canal
—the agamozobid of Cercaria ephemera, a. Oral cavity, b. Alimentary canal, c. A
developed Cercaria ephemera, d. Sporula not yet developed into Cercarim. These
sacs are found in Planorbis corneus. Fig. 2. A cercaria-sac-the agamozobid of Cercaria
ar/«a/a- provided with a very short alimentary canal and remarkable for the two short
lateral abdominal processes, found in Li/mno'us stagnalis. Fig. 3. A perfectly simple
cylindrical cercaria-sac, having no digestive canal. I found it as the agamozobid of
Cercaria sagittifera in Helix pomatia.

16

INTRODUCTION.

c^cum (where such a structure exists,) contains nothing but
yom.g Cercance, These yoTmg are developed, not from ova, but
from gemmffi, which differ essentially from ova. They are
solid, round, and somewhat flattened discs, which, growing and
developing, become little caudate worms, resembling in form and
organization certain Trematoda {Distomum, Monostomum, Diplo-
discus, Gastrostomum) } '

Fig. 4.

Fig. 5.

Fig. 6

Figs. 4 — 10. The various stages of development of Cercaria ephemera, from, the
agamozooid, fig. 1. Fig. 4. Sporula. Fig. 5. Sporula thinned at the hinder end.
Fig. 6. Sporula with this taper posterior extremity elongated into a tail. Fig. 7. The
sporula ia this stage has assumed the form of a Cercaria. The tail is already defined.
Two black pigment-spots appear on the fore part of the dorsal surface. Fig. 8. A still
further developed Cercaria. a. The oral aperture, c, d. The urinary organ, e. The
Tail. /. Two pigment-spots. Fig. 9. A fully formed C. ephemera (one millimetre long).
a. Oral cavity, b. Alimentary canal, c, d. Urinary organ filled with granular iirine.
e. Tail. /. Three Wack spots on the anterior part of the dorsal surface. The median
pigment only begins to be developed in the last stage of development. The whole figure
of the body of Cercaria ephemera corresponds with that of Monostomum. Fig. 10.
Four cercarise, after Filippi, from Planorbis nitidus, whose posterior sucking apparatus
(composed of two suckers, one enclosed within the other) is seen in different stages of
contraction and expansion. When the tail is cast off these Cercarice are altogether
similar to Diplodiscus.

' The Cercarice and the sacs have been so often referred to of late that I may leave

OKIGIN OF INTESTINAL WOEMS.

17

It was a loug while after the origin of the Cercarice Avas
known^ before any explanation offered itself as to how the
parasitic Cere aria-sacs in water-snails and mussels arose^ and
as to what became of the Cercarice, which^ when fully formed,
always seemed to desire to leave the bodies of the dissimilar
parents in which they had been developed ; penetrating the walls
of their sacs, and boring through the substance of the bodies of
the snails and mussels into the water, where they at first creep,
and at length paddle swiftly about by the help of their tails.

With regard to the origin of the Cercaria-s?ics, it cannot be
supposed that they proceed from Cercarice, since, in these last, no
organs of propagation are perceptible. In this perplexity the
doctrine of equivocal generation was again invoked, and it was
assumed that certain glandular caeca of the digestive or sexual
apparatus, in the snails and mussels in which Cercaria-sa.cs are
found, were converted into such sacs, and produced Cercarice by
equivocal generation. This was, of course, a mere assumption
based upon no direct observation.

Now I was so fortunate as to make a discovery by which
much light has been thrown upon the obscure history of these
Cercarice and Cercaria-s&cs.

It was in the year 1833, whilst ^ig. ii. Fig. 12.

fulfilling my duties as district
medical officer (kreisphysicus) at
Heilsberg, in East Prussia/ that
I had occasion to examine a large
number of specimens of those
Trematoda known to Helmintho-
logists by the name of Monos-
tomum mutabile, which were very
commonly found in the geese of
that locality, in the cavities which
He underneath the eyebaUs. I convinced myself that these para-

Fig 11. An infusoroid embryo of Monostomum mutabile which has just left the
egg. (See my essay on this subject in Wiegmann's ' Archiv.,' 1835, i, p. 69 ) a Sucker

La^L'oTtSrr'"'"'; a. The sporule cyst left fr'ee by thJ

death of the ihfusoro.d embryo, b. The same viewed laterally. This body closely
resembles the sporule cysts of Cercaria armata. ^

tb^i^^

gures wluch Von Bar, .„ h.s masterly ' Bcitrage zur Keuntuiss der niederen Thiere'
Nova Acta vol. x.n, pars 2a, 1826,) and Steenstrup, in his • Alternation of Genera-
tions,' have given. "cucra

2

18

INTRODUCTION.

sites^ belonging to the order Trematoda, bring fortb living
young, which assume the form of Infusoria, and SAvim about in
the water by means of the cilia which cover the whole surface
of their bodies. After some time, I observed that these embryos
apparently died, their bodies seeming to break up and gradually
disappearing, but always leaving behind a sharply defined, mobile,
cylindrical body, provided with two short, lateral processes. In
all the embryos, without exception, this body was visible through
their parietes while they still lived. To my great astonish-
ment, upon further observation of these contractile remains of
the Monostomum embryos, I discovered that they agreed precisely
in form, structure, and movement with certain young Cercaria-
sacs. Hence I ventiu'ed to conclude that the Cercaria-sacs pro-
ceed from Trematoda. At the same time, these observations
seemed to indicate hoAv it was possible for the inert, helpless
Cercaria-sacs to make their way into snails and mussels. The
Monostomwn mutabile is known to reside in such cavities of the
body of wading and swimming birds, as possess natural external
apertures ; when, therefore, the embryos of a Monostomum muta-
bile are born, they will issue without much difficulty from the
animal infested by their parents, each carrying its Cercaria-ssiC
within its body : and the habits of the infested animals are
usually such that the embryos will at once pass into water,
in which they can, by means of their cilia, swim swiftly about.

In this element, the infosory Monostomum embryos will, in-
stinctively and immediately, seek out those animals that are fit to
serve as a nidus for the further development of the Cercaria-
sacs enclosed within them. After the Cercaria-sacs have thus
passively entered, by the natural apertures, into their appropriate
animals, their carriers, the ciliated embryos which have hitherto
enclosed them, die oflF. As a sort of animated covering to the
Cercaria-sacs, they have performed their office ; and it is now left
to the young that have just been released, to work themselves
deeper into their new habitation by their own efibrts, and to
seek out those places which will afford them the necessaiy
nourishment for further growth, and for the development of their ,
brood of Cercarice.

I have not yet been able absolutely to witness this process of
immigration of Monostomum embryos containing Cercaria-sacs,
and as I have filled up the gaps in observation with my own
ideas on the subject, what really occurs may be somewhat

OKIGIN OF INTESTINAL WOEMS.

19

different; still, the immigration of the Monostomtcm embryo,
which is the principal point, must take place, since the singular
relations of the infusorial Monostomum embryos and the young
Cercaria-sacs they contain, point distinctly to this conclusion.

Every one will understand, that the knowledge of even such a
small fragment of the history of the development of the
Monostomum mutabile as this, was of the utmost value, since it
afforded the key to the long inexplicable mode of origin of the
Cercaria-sacs. There now only remained the question as to
what became of the Cercarice, and in what relation they stood to
the Trematoda. It was an old idea that there was great similarity
between the bodies of the Cercarice and certain Trematoda, viz.,
Monostomala and Distomata, and the force of the comparison was
strengthened by the fact that the CercuricB cast off their tails
after leaving the sacs, and thus become still less different from
these Trematoda. Many Distomata whose bodies are encircled
with spines at their anterior extremity, for example, Distomum
irigonocephalnm, echinatum, uncinatum, and militare, are so like
certain Cercarice, that when the latter have thrown off their tails,
any unprejudiced person would take them for the young of these
Distomata. In fact, in their whole organization, the Cercarice
are really no other than young Trematoda. The circumstance
that one never finds sexual organs in the Cercarice is strongly
corroborative of the notion that they are young Trematoda not
yet sexually developed. Here again we have to do with parasites
destined to emigrate and immigrate, that in some other situation
they may arrive at sexual maturity. The course which the
Cercarice take in their wanderings is, however, a much longer
and more complicated one, than that followed by the sexless
Gordiacei. These need only leave the insects they have hitherto
infested and withdraw into damp ground, where fully grown as
they are, and provided with the necessary store of fat in their
bodies, they can quietly await the development of their sexual
organs. On the other hand, the emigrating Cercarice are destined
to enter vertebrate animals, since it is only in the intestinal canal
of certain mammals, birds, reptiles, or fishes, that they can grow
and mature their sexual organs.

Many of my readers may be unable to conceive how it
is possible for Cercarice living in water, to enter into the
intestines of such mammals and birds as live far away fi-om
water, or, at any rate, never come into proximity with the

20

INTRODUCTION.

Fig. 13.

Fig. 14.

waters in which the Cercaria live. I can^ however^ offer a
solution of this apparent mystery, having surprised many Cercaria
in the act of migrating. Before I say anything more about
this, I must mention a peculiarity which is to be noticed
in most of the Cercariai after they have left their sacs. This is
their habit of encysting themselves, a process which is effected in
the following manner. After a Cercaria has been for some time
in the water, first creeping and then swimming about with mani-
fest restlessness, it gathers itself up into a ball, and emits from
its whole surface a mucous secretion which soon hardens, and since
inside of this mucous mass the worm, coiled up into a little ball,
turns round without stopping, invests it as it were in an egg-shell.
During this process of encysting the Cercaria invariably casts off
its tail, so that the capsule eventually encloses the body merely,
(fig. 13). For a long time I vainly wondered what could be
the object of this process, and, never understood what its
signification in Cercarian life was, until, in dissecting some

insects, I met with a fact which
suggested how I might gain the
knowledge I sought for. In the
larvse of a great number of various
kinds of aquatic insects, of Libel-
lulidce, EphenieridcB, Perlidce, Phry-
ganidae, I found encysted Cercaria?,
which I again discovered in the
same animals, after they had left
the water, and had been trans-
formed into winged insects. Not one of these encysted Cer-
caridB lodged in an insect, was either full-grown or possessed
sexual organs. I only observed one other slight step towards
their further development ; the sexual apparatus, viz., the testis,
the germarium, and the copulatory organs, were abeady faintly
indicated. As, however, perfectly full-grown and sexually
developed Trematoda are never met with in insects, I decided,
after the discovery of the encysted Cercaria in them, that they
merely sought out the insects as a temporary resting place.

Fig. 13. Encysted Cercaria ephemera, a. Sucker, c, d. Urinary organ.— Fig. 14.
Abdominal extremity of a Cercaria ephemera, in which, by the casting of the tail the
urinary organ has been opened externally, a. Inferior expanded end of the urinary
organ, g. Aperture out of which the granular urine is excreted. Before I pointed
out the true import of this urinary organ these granules were regarded as eggs, and
when the urine was excreted they were tliought to be laid.

OEIGIN OF INTESTINAL WOKMS.

21

Most of the sexually developed Trematoda are parasitic upon the
higher Vertebrata, the Cercarioe being, in fact, nothing else than
young sexless Trematoda, whose instinct it is, to pass out from
the inferior animals where they are produced, into the higher
forms in which they attain the power of sexual reproduction.
Should those CercaricB which are generated in aquatic molluscs,
be able to attain their sexual matm'ity in the intestines of
insectivorous birds or mammals alone, they can only reach the
latter locality by entering the larvae of aquatic insects, and then
becoming encysted in the manner already described. In this
condition they remain, until the new animal in which they have
established themselves, having undergone its metamorphosis, leaves
the water and is swallowed by some insectivorous vertebrate.

In the act of digestion the body of the insect is destroyed, together
with the capsule of the imprisoned Cercaria, which in this manner
finds itself transplanted into those new circumstances which are
alone fitted to permit of its further change into a sexual Trematode.

That this instinctive impulse of the CercaricB to encyst them-
selves after emigration, is accompanied by a desire to pass into
insect larvae, I assured myself by ocular demonstration. I had
procured a large number of specimens
of Cercaria armata which had emigrated
from the common Lymneeus stagnalis,
and put them into a watch-glass filled
\vdth water, in company with several live
Neuropterous larvae (of the families of
the Ephemeridce and Perlidce). I soon
observed, with the microscope, that the
Cercaria, which at first, flapping their
tails, moved freely about in the water, at
last betook themselves to the insect larvae,
and crept restlessly about them. It was
easy to see from their movements that

the little worms had some object in view. The Cercaria armata,
as is well known, is provided with a spine-like weapon, pointing

Fig. 15.

Fig. 15. A. A Cercaria armata viewed from the abdominal surface, a. Oral sucker
with the frontal spine showing through it. b. Ventral sucker, c. Digestive apparatus.
d. Urinary organ, h. Tail whose root plugs up a pit in the hinder end of theliody.in
which the urinary organ opens.— fi. The same Cercaria viewed laterally a, h, d, have the
same signification.— c. The frontal spine. The alimentary canal is left out in this
view.— C. The frontal spine of thisCercaria very much magnified, and viewed from above.

22

INTRODUCTION.

forward from the centre of the animal's head. (Fig. 15 B.) I
could readily perceive, that these Cercarue which I was observing,
fr-equently paused in their inspection of the insects, and inserted
this weapon into their bodies as they crept over them. This
probing experiment, for it was clearly nothing else, was repeated
again and again, until the lai'va had discovered one of the soft
places between the segments of the insect's body; this being
reached, it never moved from the spot, but worked incessantly
with its spine, until a way was bored through the soft place it had
fastened on. Scarcely was the point of the spine fairly through,
ere the supple worm inserted his thin anterior extremity into the
wound, widened the opening a little, and by degrees drew in his
whole body, which became wonderfully slender under the opera-
tion. The tail of the Cercaria was not drawn inside the insect,
but remained hanging outside the puncture, being doubtlessly
seized and nipped off, by the sudden closing of the wound when
the body of the Cercaria had slipped through. Having selected
very young and delicate Neuropterous larvse for my inquiry, the
transparency of their bodies enabled me to continue to observe
the tail-less Cercaria after their entrance ; they forthwith lay
still, drew themselves up into balls, and surrounded themselves
with a cyst. During the process of encysting, the frontal spine
fell off from the body of the Cercaria, and lay apart by its side,
but enclosed within the cyst.^ This weapon.
Fig. 16. therefore, undergoes the same fate as the tail of

these animals, each apparatus being cast aside
after fulfilling its intended end.

The impulse to immigrate and become en-
cysted is so strong in all the Cercaria, that
their efforts appear to be occasionally over hasty,
and perhaps lead them altogether astray.
I have found in Aselli and Gammari, encysted Cercaria, which
in every way resembled those which had passed into insects.

Fig. 16. An encysted Cercaria armata. a. Oral sucker. b. Ventral sucker,
c. Digestive canal which is connected with the oral sucker, d. Urinary organ
filled with granular urine, e. Cast off frontal spine which now lies free in the cavity of
the cyst. /. Aperture of the urinary organ, which hecomes visil)le after the tail is cast
off. g. Cyst in which the tailless Cercaria remains encysted as an asexual Distomiim.

1 The ohservation above detailed (which I have already published in Wagner's
' Ilandworterbuch,' Bd. ii, p. 669,) can be easily repeated, since the sacs of Cercaria
armata are excessively common in our fresh-water snails.

ORIGIN OP INTESTINAL WORMS.

23

Now, if these Cercaria can only attain their sexual maturity
in the warm-blooded vertebrate animals, which devour in-
sects, and therefore seek their food in the air or on land alone,
the Cercarice, that had established themselves in the Aselli and
Gammari, would wait in vain for the time to arrive when they
should be transported into the air, since the animals in which
they were domiciled would never quit the water. Again, many
Cercarice, in their haste, become encysted incautiously at so early
a period, that the purpose of the process is defeated.

I have already shown that the emigrated Cercaria ephemera
attaches itself to water-plants, or any other objects in the water,
by means of the cyst which it elaborates ; other Cercaria even be-
come encysted before they quit the body of the aquatic snail in which
they were generated ; whilst some, again, have even been found
encysted within the Cere aria-sacs} Steenstrup takes this to be
a normal phenomenon ; I should only consider it such, provided
that the encysted Cercaria in the snails are intended to attain
their sexual maturity, in the intestines of fishes or of water-bii'ds
feeding on snails.

Although the various facts I have communicated can only be
regarded as fragments of the natural history of certain Trematoda,
they are yet capable of being connected into a whole, if the
theory of the Alternation of Generations be extended to them.
For instance, from the foregoing statements, we perceive that certain
sexually matured Trematoda {Monostomum, Distomum) generate
young within their sexual organs, which are not developed into
sexual individuals similar to their parents in form and structure ;
but that, on the contrary, each embryo is converted into an
animal of remarkably different form, viz., into a Cercaria-s&c,
which has the import of a sexless nurse, since without possessing
sexual organs, it nevertheless generates young Cercaria. These
Cercaria again differ from their parents, but gradually become
sexually perfect, and in form and structure take the likeness of
their grandparents. The several embryos of these Trematoda,
therefore, do not pass into an equal number of new and separate
sexual Trematoda, but each embryo produces a nurse, which, by
asexual generation, brings forth a greater or less number of
sexual Trematoda.

' Steenstrup (1. c., p. 85, pi. iii [English translation]), has more particularly described
and figured such Co-caria-sacs containing encysted Cercarice.

24

INTRODUCTION.

If we follow those Trematoda which are subject to the
Alternation of Generations, in their wanderings, we shall see
that they are likely to meet with many obstacles to the
completion of their developmental course, which is the entering
into the viscera of an animal in which they can become sexually
developed. It may happen that the various emigrations and
immigrations of the infusorial embryo, or of the tailed Cercarice,
may miscarry ; or it may be, that the exact time for the Cercaria
to become encysted may be missed ; or that after the due occur-
rence of the encysting process, the insect selected for its penulti-
mate habitation may die at an inappropriate time or place, and
so prevent the encysted Cercaria from reaching the last animal,
or that one fitted for its final residence. This destruction of the
various forms of Trematoda by untoward circumstances is com-
pensated by the fact, that they are furnished by the Alternation
of Generations with the means of greatly multiplying the various
developmental stages of their descendants. By these means the
propagation of these animals is secured, since, notwithstanding the
mishaps by which many are arrested or destroyed, a sufficient
number of individuals always remains ou.t of the numerous young
of the nurses and larvae, who, in spite of all obstacles, achieve the
end in view — the propagation of their species.

The history of the Cercarice enables us to comprehend many
phenomena which were necessarily quite erroneously interpreted
by the older helminthologists, who were ignorant of these wan-
derings and unacquainted with the occurrence of the Alternation
of Generations. It is a common thing to find capsules or fcysts,
in the midst of the tissues of the most widely difi"erent organs of
men and animals, containing asexual and only partially developed
intestinal worms. It was difficult to understand how such living
Entozoa could have originated in the viscera of animals (sometimes
in those which are deeply seated and cut off from all external
communication) and could here propagate their kind. Hence it
was taken for granted that they had been produced by equivocal
generation from the surrounding parts, and the mode of origin
thus assumed, conversely furnished the reason why these Entozoa
were unprovided with sexual organs. Frequently too, free,
young, or imperfectly developed intestinal worms were met with
in the substance of organs, and their occurrence was in the same
way attributed to equivocal generation, though in reality these
Entozoa were either in the act of emigrating or of immigrating,

ORiaiN OF INTESTINAL WORMS.

35

or else, having found a resting place in some organ, were tarrying
till tlie creature they infested should be swallowed by some other
animal, when the passive immigration for which they waited

would take place.

Many wandering parasites are unresistingly suffered to bore
their way into and remain in, the organs of animals, whilst
on the other hand, certain kinds are arrested and finally stopped,
by becoming enclosed in a coagulable lymph thrown out by the
organs which they traverse. Hereafter we shall have to dis-
tingiiish two kinds of encysted intestinal worms. In the one
kind the cyst is thrown out by the parasite itself, as I have
already explained in the case of the Cercarice ; in the other, the
organ in which the encysted parasite lies imbedded, furnishes the
walls of the cyst. These last " extrinsic" cysts are easily recognised
in the passively encysted parasites of vertebrate animals, being
immediately and intimately connected with the neighbouring
tissues and traversed by blood-vessels.

In such capsules or cysts are found the most diverse kinds
of intestinal worms, whose further course may be very
various.

Many of the encysted young of the intestinal worms experience
no further change, but only remain for a longer or a shorter period
until such time as they .may, together with their host, pass into the
intestine of some animal of prey suitable for their future develop-
ment. To this kind belong the Cercarice I have already mentioned
(page 20). There is also a small, imperfectly developed, round
worm, hitherto always erroneously described as a perfect intesti-
nal worm, under the name of Trichina spiralis, which remains a
long time in its cyst without either growing or developing sexual
organs. This minute Trichina spiralis is not only met with in
the substance of the muscles of man, but also in the pleura and
peritoneum of the most widely difierent kinds of vertebrate
animals, enclosed in oval capsules about a quarter of a line in
length. Most probably a certain time of imprisonment is allotted
to the little worm, and after this period has elapsed, should its
deliverance not be effected by passive emigration, it dies, and its
body, which has not in the least increased in size, is, without
changing its outward form, transformed into a brittle glassy mass
composed of carbonate of lime. This process of calcareous de-
generation also takes place in other encysted and dead intestinal
worms, in which, however, the form does not always remain

26

INTRODUCTION.

perfect, but is either more or less altered, or else entirely
destroyed.

Other encysted intestinal worms succeed in obtaining nourish-
ment through the walls of their prison, and thus go on growing.
Those, however, amongst the encysted entozoa, which are in-
tended by nature to attain their sexual maturity only in the
digestive organs of certain animals, cannot arrive at this condition
in their cysts, and must, in spite of their further growth, fail in
the attainment of the power of sexual propagation, until the
animal they inhabit is devoured by the predacious creature,
whose intestine is alone fitted to allow of the passage of these
asexual intestinal worms into the last stage of their development.
I may cite here, as examples, various Nematoidea and Cestoidea.
In many marine fishes the liver is covered with capsules, which
often contain a well-grown nematoid worm more than an inch
long. Naturalists have arranged this parasite among the in-
testinal worms as Ascaris capsularis, Filaria piscium, Filaria
cystica. I have never met with one of these round worms con-
taining developed sexual organs. As in their further organization
no less than in their whole form, these ascarids most strikingly
resemble certain sexually-mature nematoid worms, namely,
Ascaris osculata, spiculigera, angulata, aucta, and others, which
infest the alimentary canal of seals, cormorants, divers, gulls, and

predacious fishes, the idea presents
itself that these encysted, not yet
fully developed Nematoidea belong to
either one species or another of the
last-named Ascaridce. More par-
ticular inquiries into the subject will
instruct us what species of these
round worms, which are now con-
sidered to be distinct species, will
hereafter have to be united into a
single group, as younger or older individuals of one and the
same species. The sexless Ascaris incisa, represented in fig. 17,

Fig. 17. A convoluted piece of the intestine of the mole (nat. size), with many flat-
tened, pedunculated cysts, each enclosing a little thread-worm, attached to its peritoneal
investment. * * Such cysts viewed edgewise, b. A single capsule much magnified,
80 as to render the enclosed thread-worm more clearly visil)le. This parasite belongs to
that group of the Ascaridce whose intestine is provided anteriorly with a cajcum directed
upwards.

Fig. 17.

OEIGIN OF INTESTINAL WORMS. 27

/

which occurs encysted in the peritoneum of the Mole, must also
be awaiting its transference to the intestine of some other anial,
where it attains its sexual maturity.

From what has been stated we gather, that those young intestinal
worms which are developed at a distance from the nidus of their
parents, succeed, in the end, in reaching those situations where
they may repeat the part of their progenitors, and reproduce their
kind. Impelled by instinct, the embryo parasites, that have only
just left the egg, disperse in all directions, so that they may
immigrate into other animals, whenever an opportunity offers.
Many thousands of these embryos of necessity never attain their
object, on account of the numerous casualties that beset them in
their wanderings. The point of most importance is, that these
embryos should select, as their temporary residence, such crea-
tures as will be consumed by those animals, whose intestine served
their parents, as a habitation and birth-place for their young.
But many of these young, immigrated, intestinal worms will
have undertaken their journey in vain, and will die without reach-
ing the last stage of their development, in consequence of their
host and involuntary carrier, escaping from his natural enemies.
Again, many embryos will be led astray by the migratory im-
pulse, and pass into animals which never become the prey of those
whose digestive canal is then* goal. This I conclude from the
frequent occurrence of one and the same kind of encysted para-
site amongst the most various kinds of animals. And I shall
regard those embryos which have failed in their object, in the
way I have mentioned, as parasites which have strayed in their
wanderings.

I know that there may be some difficulty in accepting this
theory of strayed parasites ; it will be urged that these, like all
animals, have a sort of instinct implanted in them which never
allows them to enter upon any fruitless undertaking, and which,
without their knowing it, impels them to strike out the right
path in their wanderings. If this were really the case, every
tsenioid embryo must some day become a tape-worm, and we
should be so overrun with nematoid worms that, judging from
the enormous quantity of their eggs, the animals they infest
would perish by wholesale from their countless numbers. Those
who have occupied themselves with the collection of intestinal
worms, must only too frequently have remarked, however, that these
parasites are by no means so numerous as the immense numbers

28

INTEODUCTION.

of their eggs would lead one to suppose. This inclines one
more readily to the belief that nature, seeing how full of diffi-
culties is the way of these parasites to sexual development, has
endowed them with the power of generating millions and
billions of eggs, when once they have overcome these obstacles
and developed the necessary sexual organs. Through the un-
ceasing spread of cultivation, the decrease and extirpation of
certain animals, on the one hand, and the taming and increase of
domestic animals on the other, the conditions of life of many of
the intestinal worms have become so changed, and so widely
diflFerent from their original state, that, with their inherent
tendency to wander, many of these parasites must often go
astray.

The Trichina spiralis, which is found in human beings, and
which, as I have already shown, must be regarded as an encysted
sexless nematoid worm, can hardly have found its way into the
muscular substance of man, except by having gone astray ; so also
the Cysticercus cellulosce, which not unfrequently appears in the
muscles and other organs of man, and which, as I shall hereafter
show, is an asexual tajnioid agamozooid. The Cysticercus cellulosa
changes to a sexual tape-worm in the intestinal canal of certain
mammals ; the Trichina spiralis, after transportation to another
and more favorable situation, will also become sexually de-
veloped. That these two parasites should have been originally
intended to pass into and establish themselves in, human beings,
waiting for the opportunity to emigrate, which could only occur
when the person who harboured the sexless parasite should be
devoured by some appointed beast of prey, is an idea insufferable
to the dignity of man,^ which every reader of these lines must of
necessity reject ; and admit, instead, that the appearance of these
parasites in the interior of man can only be accounted for by
the fact of their having gone astray.

Many of the young of the intestinal worms which only attain
the last stage of their development in the digestive canal of the
Vertebrata, chance, in the course of their wanderings, to pass
into the wrong organs ; for instance, into the muscular substance,
the liver, or the peritoneum; here they remain undeveloped,

' To appeal to the " dignity of man" in a zoological argument appears a little out of
place. Nature seems to have had small respect for our "dignity" when she created Ihe
fleas, lice, and hugs which annoy us ; the Ascaris, which reduces us below the level of
the beast ; the Strongylus, and the Echinococcus, which destroy us outright.— [Ed.]

OEIGIN OF INTESTINAL WORMS.

29

whilst other individuals of the same brood, which have found
their way into the intestine of the same animals, arrive at
matui-ity. Tricenophorus nodulosus, infesting fishes, offers an
example of this, developing into a long, sexually-mature tape-
worm, in the intestines of pikes and perch, whilst at the same
time these fishes often harbour other tape-worms, which are,
however, always sexless, in cysts in their liver. These last must
certainly be also regarded as strayed parasites.

In these wanderings through the bodies of vertebrate animals,
the very small embryos of the intestinal worms, boring their way
through the walls of the blood-vessels, not unfrequently fall into
the current of the circulation, and so become distribvited with the
blood. In fact, embryos of intestinal worms, to which the name
of Hcematozoa has been given, have often been discovered in the
blood of birds, reptiles, and fishes,^ These Hcematozoa neither be-
come further developed in the blood, nor increase in size ; but many
of them, whilst circulating in the vascular system, stick in the narrow
blood-vessels of certain organs which afford a more congenial soil
for their further growth ; such at least is the most natural way
of accounting for the appearance of intestinal worms in the
brain, in the spinal marrow, and in the eyeball of man and
animals. These organs are so completely enclosed, partly by
bones, and partly by dense fibrous membranes, that before the
existence of animals in the blood was known, it was supposed
quite impossible for parasites to penetrate into such well pro-
tected organs ; but that they must have originated then and
there through equivocal generation. The Cysticercus cellulosce,
the Coemrus cerebralis, and the Echinococcus hominis and Veteri-
nomm, have long been known as occasional denizens of the brain
and of the spinal marrow in men and animals, and have, up
to the very latest times, served as a stronghold for the sup-
porters of the doctriue of equivocal generation. Having sub-
jected these very cystic worms to particularly close inves-
tigation, iu order to confute this fabulous hypothesis as to

1 I have collected together the different observations on hajmatozoa in the article
«' Parasiten" in Wagner's ' Hand-worterbuch' already referred to (p. 648) ; subsequently,
new facts of the same kind have been published by Ecker (MliUer's ' Archiv.,' 1845,
p. 501), Wedl (in his ' Beitrage zu Lehre von den Hiimatozoen,' Wien, 1849), and
Leydig (in Miiller's ' Archiv.,' 1851, p. 227).

[See also the remarkable observations of Bilharz, ' Ueber das Distoma haematobium,'
' Zeitschrift flir Wiss. Zoloogie,' 1852. This dioecious bjematode is found in the portal
Oloodofman.] — [Ed.]

30

INTRODUCTION.

their mode of origin^ I will give au account of the results
below.

With the migrations and alternation of generations amongst
the intestinal worms^ two other phenomena are connected^ which
were formerly quite unnoticed, but which now, since attention
has been directed to them, have been very generally observed. In
the neighbourhood of those sexually perfect intestinal worms
which, in their wanderings, are subject to the alternation of
generations, only eggs, or recently hatched embryos are met with ;
but the further stages of development are always wanting,
since they first make their appearance after the emigi'ation of
the young to other places. Further, many of these intestinal
worms, taken whilst in the act of migrating, are never found
below a certain size, since they do not commence their wanderings,
either as nurses or larvse, until they have already reached a certain
stage of their development.

In this chapter I have expressed myself somewhat at large
upon the wanderings and alternation of generations of the intesti-
nal worms, in order that I may be fully understood in the
ensuing ones, when I have occasion to refer to this generation
by agamozooids. The history of the propagation of certain para-
sites, in the foregoing pages, may seem new and astonishing
to many readers, and yet the alternation of generations is not
more wonderful than metamorphosis. We have been so long
acquainted with the way in which metamorphosis takes place in
the higher and lower members of the animal kingdom, that we
no longer wonder at the various transformations of the frog, nor
gaze with surprise when a caterpillar becomes a chrysalis, and
after a certain time flies off in the shape of a butterfly. The
many to whom the metamorphosis of frogs and insects is a
common appearance, forget that there was once a time when it
was unknown, and when the multiplication of grubs and larvae
was ascribed to equivocal generation, their true origin being
unsuspected. It is to be hoped that a time will also arrive
when the complicated alternation of generations wiU not be
known to naturalists alone.

CHAPTER II.

ON THE TAPE-WORM.

The tape-worms [Cestoidea) constitute a peculiar group of
entozoa which only attain their perfect development and sexual
maturity in the intestinal canal of vertebrate animals. Those
that are often met with in other internal organs than the
intestinal canal, in fishes, reptiles, birds, or mammals, or in the
interior of inferior animals, are always sexually undeveloped.
In this sexless state the tape-worms wait for an opportunity to
pass out, which occurs when the creature they lodge in is swal-
lowed by some vertebrate carnivore. It is only when such sexless
tape-worms have thus passively effected their entrance into the in-
testinal canal of the appropriate Vertebrata, that their sexual matu-
rity takes place, and they become capable of laying eggs for further
propagation. In this wandering the remarkable circumstance
occurs, that whilst these undeveloped tape-worms pass into the
stomach of the predacious animal in a more or less uninjured
condition, and establish themselves in its intestine, the soft parts
of their former host yield to the digestive juices. Numerous
examples attest the truth of this assertion, but of these I will
only select the following.

In certain neighbourhoods the sticklebacks are infested by a
kind of tsenioid parasite which lies free in the cavity of the
abdomen, and often distends the body to an unusual size. This
parasite has been before described under the name of Bothrio-
cephalus solidus. In the stickleback its joints and sexual appa-
ratus are undeveloped and always remain so.

In the intestine of many of the water fowl which prey upon
these sticklebacks, a sexually matured tape-worm, known to
naturalists by the name of Bothriocephalus nodosus, has been
found. This is no other than the Bothriocephalus solidus in a
further stage of development ; after its former host, the stickle-
back, has been digested in the bird's stomach, it is released,

32

THE TAPE- WORM.

and entering uninjured into the intestine of its new owner,
arrives at sexual maturity. The extent of development in each
individual will be found to be in proportion to the time it has
passed in the bird's alimentary canal after its passive emigration.
Since the connection between Bothriocephalus solidus and nodosus
has been known, helminthologists have ceased to regard these
two tsenioid worms as different species, but in accordance with
the suggestion of Dr. Creplin, who first drcAv attention to the
relationship between them, they have been considered to be
different stages of the same species, Schistocephalus dimorphus.
A similar instance occurs in the case of the Ligula simplicissima,
infesting the abdominal cavity of various species of carp, whose
sexual organs are, and remain, undeveloped, as long as the worm
remains within the fish, whilst when the latter is eaten by, and the
entozoon thereby conveyed into the intestines of, ducks, divers,
waders, and other water-fowl, it attains perfect sexual develop-
ment. In the older helminthological systems the sexually ma-
tured Ligula simplicissima is described under various specific
names, sometimes as Ligula sparsa, unisei'ialis, sometimes as
Ligula allernans, or interrupt a.

Many Cestoidea, during their youth, lodge in the liver and
peritoneum of fishes. In these organs they excite a morbid
exudation whereby a membranous substance is produced, which
forms a kind of capsule round the worm, and thus, as it were,
excludes it from the organism. This act, by which the organs
seek to free themselves from such unwelcome guests, I shall
designate by the name of " extrinsic"^ encysting process already
given in page 25.

The encysted Cestoidea increase in size, but do not become
sexually mature, from the absence of the conditions necessary
to the attainment of this state; and should then- hosts perish
without having been devoured by an animal of prey, the sexless
Cestoidea will die with them, without leaving any progeny.
Various examples illustrate the truth of this statement.

Mention has already been made (at page 29) of the Triaeno-
phorus nodulosus which infests the intestme of the pike and
the perch, where alone it is to be met with sexually mature.
Helminthologists, however, give other localities of this worm, as

1 I liave added the word " extrinsic" here to distinguish this from the self-encysting
process by exudation from the entozoon itself.— [Ed.]

ENCYSTED CESTOIDEA.

33

certain species of salmon, for instance ; but in these it is met
M-ith encysted in the liver and peritoneum, and is invariably
sexless. The examination of the livers of a great number of
the Salmo salvelinus caught in the Konigs-see, near Berchtesgaden,
recently convinced me that this worm can only attain to sexual
maturity in the alimentary canal of perch and pike. These livers
Avere covered with various sized cysts containing larger or smaller
individuals of Tricenopliorus nodulosus, which were every one
sexless. The Cestoidea were obviously awaiting their sexual de-
velopment, which could only take place when they should have
passed into the intestine of a pike or perch, a migration which
may easily occm-, since the lake is full of such predacious fish,
who are always ready to seize upon the salmon. When the
Tricenophorus nodulosus has come to sexual maturity and has
deposited its eggs in the intestine of the pike and perch, these
eggs will be passively extruded, since the cestoid embryos are
never hatched in the spot where they have been laid ; that is to
say, they will be expelled Avith the faeces through the anus of the
fish. With regard to the ultimate fate of the young of the
Trimnophorus nodulosus, I can state nothing from actual know-
ledge, but from what has been observed in regard to other intes-
tinal parasites, I think one may infer that the young of the
former will be impelled by the same instinct, to wander, and to
seek that situation which can alone develop their powers of repro-
duction. Although I am unacquainted Avith the form in which
the embryos of the Tr'mnophorus nodulosus commence their
wanderings, yet, having found tolerably large individuals of this
species encysted in the livers of various fishes (of salmon,
sticklebacks, millers' thumbs, burbot, blennies, and others), I
conclude that the young Trianophori have merely made these a
temporary resting-place, and are waiting till their host becomes
the prey of the above-nained fishes. Whether the young of the
Tnanophorus always avail themselves of an intermediate host by
whom they may be conveyed into the intestine of their final en-
tertainer, the pike or perch — I cannot say. It is possible that
they may pass, at once, into the pike or perch whenever an
opportunity offers ; but under these circumstances it would be by
no means immaterial into which organ of the fish they first
entered. Since the intestinal canal is the only proper place for
their sexual development, they will, by passing into the liver or

3

34

THE TAPE-WORM.

peritoneum, most assuredly meet with the same fate as if they
had entered the other fishes; they Avill become encysted, and
may grow within the cysts, but will not become sexually matm-e
unless their owner be swallowed by a larger creature of his own
kind.

Similar migrations and strayings from the right path are
exhibited by the Tcenia longicollis and ocellata, Avhich are met
with, not only in the intestine, but also encysted in the livers, of
salmonoid and percoid fishes, in a jointed but sexless state. I
must call attention to the fact that the Tricenophorus nodulosus,
in its sexless condition, is not uncommonly found in the liver and
peritoneum of the sticklebacks ; and as this fish, on account of its
spines, is generally avoided by the pike and perch, the immi-
grated young of the Tricsnophorus in the sticldeback must be
certainly regarded as having gone astray.

The various species of the cestoid genus, Tetrarhynchus, enu-
merated by systematic helminthologists, are nothing more than
imperfectly developed, sexless forms of Cestoidea^ which, in their
fully developed and sexually mature condition, have been regarded
as belonging to an entirely distinct genus. Following E,udolphi,
later helminthologists termed this latter genus, Rhynchobothrium.
The genus Tetrarhynchus must now, however, be set aside,
since the forms of animals hitherto included in it must be
considered as younger stages of development of true Rhyncho-
bothria. The head end of many kinds of Tetrarhynchus, with
its four protractile proboscides, armed with numerous sharp
grappling hooks and provided with four moveable suckers, in
form and organization resembles so exactly the fore part of the
Rhynchobothria, that there is no doubt as to the origin of the
former.

The Rhynchobothria in their full grown and sexually matured
state, are only found in the digestive canal of plagiostome fishes.
In order to secure their migration into other individuals of this
order, the young of the Rhijnchobothria make use of such
marine creatures as serve the former for prey. As the ravenous
shark or ray is not over nice in the choice of its food, it is
not necessary for the young Rhynchobothria to select any par-
ticular marine animal as its temporary host, in order to introduce
itself into their intestine. Indeed one meets with Tetrarhynchi,
(that is to say young Rhynchobothria), in soles, flounders, mullets,

THE SCOLEX-STATE.

35

ill cod-fisli, gurnards, congers, and even in cuttlefishes. From
the encysted condition in which the parasites are found in these
animals, it is easy to see that they have only made them their
temporary abode. That they are by no means at home in these
intermediate hosts seems evinced by their lively and restless
proceedings; their four protractile feelers, with their countless
hooks, being employed most cleverly, to bore through the flesh,
the walls of the stomach, and the tunics of the various organs.

The head end of the young Cestoidea takes, at a very early
period, the form of that of their sexually matured parents, whence
it is easy to distinguish to which species of cestoid worm they
belong. According to Van Beneden's suggestion, helminthologists
have desig-nated such undeveloped sexless Cestoidea whose heads
have already assumed the parental form, as " scolices." From
their physiological signification these cestoid scolices have been
compared with the larvse of insects ; the comparison, however, is
not tenable, since every insect larva leaves the egg in its larva-
form, and is gradually changed into an individual insect capable
of propagation, whilst the scolices of the Cestoidea do not come
forth from the egg in the condition of scolices, nor are converted
into a reproductive tape-worm individual, but by sexless genera-
tion give birth to a great number of sexual individuals. Here,
therefore, we have to do, not with metamorphosis, but with an
alternation of generations in which the scolex-forms play the
part of agamozooids.

In studying the history of the Cestoidea, it must be strictly
borne in mind that all scolices, whatever be their form, are only
different stages of cestoid worms ; and, on the other hand, that
the cestoid embryos leave the egg in a form widely different from
a scolex. The embryos of the genera Tania and Bothriocephalus
are precisely similar, widely different as are the forms of the
so-called " heads " of these worms subsequently. The whole or-
ganization of these embryos seems specially adapted for the pm'pose
of digging and boring, a circumstance most favorable to them in
their wanderings. They possess, in fact, a very small rounded
body, (fig. 18 a), at one end of which six little hooks or claws
project, two in the middle and two on each side. Each pair of
these hooks is differently shaped from the others (fig. 18 b, c, d),
and they are so arranged, that one of each form is placed on each
side of the embryo, so that the two innermost, the two middle.

36

THE TAPE- WORM.

and the two outermost hooks are alike.^ If one of these embryos

is set free (which can be effected by care-
fully crushing the eggshell between two
plates of glass), without destroying the
living tape-worm embryo, its various
movements may be examined under the
microscope. It draws its round body
together, and enlarges and contracts its
transverse diameter, and by this operation protrudes, first in
front and then at the sides, the six little hooks from that end
of its body which, from these hooks being situated there, I shall
call the fore part. The observer can readily understand how, by
such movements, the excessively minute cestoid embryo succeeds
in boring its way into the moist and tender soft parts of other
animals and in traversing their interior in all directions.

When the cestoid embryos have, by immigration and subse-
quent encysting, lodged themselves in an animal by whose
means they will eventually become introduced into the alimentary
canal of one of the Vertebrata, and so reach the last stage
of their development, a remarkable metamorphosis takes place
by which they pass from the condition of embryos into that of
scolices. In the interior of the embryo an organ is developed
which gradually assumes the characters of the head of a cestoid
worm, and always resembles that of the particular species fi'om
which the embryo has been produced. When once the head of
the cestoid is frilly formed it may become extruded from the
interior of the body, and the entire worm then constitutes a scolex.

The whole of this process of scol ex-development may be justly
compared to an internal budding.

According to the view of the earlier helminthologists, the
scolices consist of the head end of a cestoid worm, out of whose
posterior extremity the proper body is subsequently developed.
In regard to the organization of the scolices, it must be par-
ticularly noted that they possess no oral aperture, and are only
nourished by the absorption of fluids through the surface of their

Fig. 18. The embryo of Txnia crater if ormis. The six hoolclets are formed upon
three different types; b, c, d, represent the three kinds more highly magnified, b. One
of the two uppermost, c, one of the two median, and d, one of the two outermost
booklets.

• See my description of these hooks in Burdach's ' Physiologie,' Bd. ii, 1837, p. 204.

DEVELOPMENT OF SCOLICES.

37

integument. In the substance of their bodies, spherical or
cliscoidal bodies of a glassy appearance are often seen: these

Fig. 19.

have frequently been mistalten for eggs, whereby the nature of
these creatures has been wholly misconceived. The particles are,
in fact, nothing more than organized deposits of carbonate of
lime. Integumentary concretions of the same kind are found in
many other of the lower animals. The scolices have also been
described as young cestoid worms : we shall, however, more
readily comprehend the various stages through which the Ce*-

Fig. 19. Series of developmental stages of a TefrarJiynchus, or rather of a scolex of
Rhynchobothrium, represented diagrammatically, and partly after Van Beneden. The
cestoid embryo becomes a receptaculum scolicis by the development of a scolex in its
interior. With the progressive development of the scolex the body of the embryo
[receptaculum scolicis) and the cyst containing it, increase in dimensions. 1. The
encysted embryo. 2. The encysted embryo developes a bud internally, and so becomes
the receptacle of a scolex. 3. The internal bud out of which a scolex is being developed
has increased in size. 4. In the interior of the bud the head of the future Tetrarhynchus
appears, and the suckers become perceptible. 5. The head of the Tetrarhynchus
becomes more clearly defined ; and, 6, acquires a neck. 7. The neck elongates, the four
hooked proboscides make their appearance. 8. The more elongated neck is forced to
become curved in order to accommodate itself to the narrow space in which the scolex
is undergoing its development. 9. The adult scolex out of its cyst, and beginning to be
extruded from its receptacle. 10. The extruded scolex; which, in 11, has separated
itself from its receptaculum. In this condition, the scolices of the Rhynchobothria
have hitherto been described as species of Tetrarhynchus. * Scolex. ** Receptaculum
scolicis. *** Cyst. For the further development of the Tetrarhynchus into ti Rhyncho-
bothrium, see fig. 23.

38

THE TAPE-WORM.

toidea pass, and be better able to bring them into unison with
the phenomena presented by the other entozoa, if, as has been
suggested above, we regard the scolices as agamozooids.

In taking this view of the nature of the scolices of the
Cestoidea, Ave assume that they are in that condition in which
they may, by asexual reproduction, bring forth a series of
sexual individuals. This in reality takes place, but only in the
intestinal canal of vertebrate animals. Before entering more
fully into the description of this process, however, it is advisable
that I should refer to certain facts, known to helminthologists,
which prove that the scolices really originate in the cestoid
embryos furnished Avith six booklets. In this matter I avail
myself of the CAddence of Stein of Tharand, who made the fol-
lowing important observations.

Stein discovered,^ on the exterior of the stomach of the meal-
worm (the larva of the coleopterous Tenebrio molitor), small cysts
about the size of a pin^s head, containing a cestoid embryo in whose
body a more or less fully developed scolex was included. In
those that Avere fully developed Stein recognised a perfect Taenia
head. Stein distinctly convinced himself that the Tania embryo did
not become a scolex by simple growth, but that the latter was
produced by budding in the body of the embryo, having, amongst
the numerous cysts that he examined, the most various transi-
tional forms, ^'om the simple unaltered embryos to those con-
taining" a fully developed scolex. During this development of
a scoliciform agamozooid the embryo changes its form, growing
rather longer on the one side than the other, in consequence of
which its six hooks become irregularly scattered over the upper
surface of the body and lose their import (fig. 26) ; a clear
proof that they do not enter into the formation of the circlet of
hooks of the tsenioid scolex. It is clear that these tsenioid
embryos arrive by immigration into the abdominal cavity of the
meal-worms, and in fact, as Stein suspected, through the walls
of the stomach; for this observer more than once found tfenioid
embryos in the stomach of meal-worms, which, judging fi-om their
form, could only just have been hatched. Most likely these
minute embryos had been taken in with their food by the meal-

1 See his ' Beitrage zur Entwickelungsgeschichte der Eingeweidewiirmer,' in the
' Zeitschrift fiir Wissenscbaftliche Zoologie,' edited by Kolliker and myself. Bd. iv»
1853, p. 207.

DEVELOPMENT OF SCOLICES.

39

worms, and so conveyed into tlie stomach. By the help of their
six booklets they pierce its walls and pass into the perivisceral
cavity. Having got thus far, the immigrated tajnioid embryos
find in the meal-worms a fitting intermediate residence, and the
scoliciform agamozooid begins to be developed in them. The
embryos having thus completed their wanderings, and arrived at
their appointed end, throw ofi" their boring apparatus, and play a
more subordinate part, the scoliciform agamozooid developed
within them, henceforward taking the chief place. The scolex is
itself sexless, but by asexual generation will bring forth sexual
individuals ; this, however, can only take place in the intestine of
some vertebrate animal, and it is now the turn of the scolices to
wander, in order that they may pass from their intermediate host
into their final one.

In doing this the nurse is entirely passive, waiting until
its intermediate host shall be devoured by that particular verte-
brate animal which is fitted to serve as the nidiis for its sexual
stage. What vertebrate animal this is, is at present unknown,
so that I can only speak conjecturally, and indicate that these meal-
worms are the favorite food of various small mammals, such as
rats and mice, and of numerous birds, the red-start^ for instance ;
and that the Tenebrio molitor, which flies about, and is produced
from the chrysalis of the meal-worm, is often caught and eaten
by bats, swallows and other insectivorous animals. A minute
comparison of the scolices of the meal-worms with the heads
of tape-worms from the intestines of the animals I have named,
may perhaps assist in filling up the gaps in these observations.

Another observation made long ago by myself, and which has
since been more fully worked out by Dr. Meissner, serves to
confirm the observations of Stein. In the substance of the pul-
monary sac of Ai'ion empiricorum, (a slug), I discovered many
encysted scolices,^ from the shape of whose heads I judged that
they formed part of the developmental series of a Tania. The form
of these scolices, is, however, very different from that of those
which are found in the meal-worms. Their head end is always
involuted in the short, and only partially developed, hinder
part of the body (fig. 20, 21).

One sees in the whole arrangement of the various parts of the

' See my essay ' Ueber den Generationswechsel der Cestoden,' in the ' Zeitschrift fur
Wissenscliaftliche Zoologie,' 1850, p. 202.

40

THE TAPE-WOEM.

Fig. 20.

Fig. 21.

encysted scolex with the retracted head, that the latter is pro-
duced m exactly the same manner as that of the meal-worm

scolex described by Stein, viz., by in-
ternal budding, although I have never
chanced to meet with such earlier stages
of development of the scolex in the slug.
However, that they do directly emanate
from T(pnia embryos, is e^ddenced by the
three pair of hooks or claws, which are
firmly fixed in the substance of the sur-
face of the posterior extremity of the
body of these retracted scolices. We are
indebted to Dr. Meissner for the discovery that these six claws are
the remains of the embryonic condition of these cestoid agamozooids.^
The encysted scolices in the slug, therefore, are perfectly analo-
gous in form and signification to the cestoid agamozooids in the
meal-worm, with this diSerence, that the first are not elongated
into a tail at the posterior extremity. The encysted cestoid
agamozooids in the slug are evidently the result of the immigra-
tion of cestoid embryos, and yet in spite of the fact that
these parasites are very frequently met with in slugs,^ I have
not been able to determine which species of Tfewm- embryo passes
into this form of scolex, nor into the intestine of what particular
vertebrate animal the scolex of the slug must emigrate, to give
rise to sexual individuals.

The sexually matured individuals of the Cestoidea are no other
than their full-grown joints; in which are developed the male
and female genitalia, by whose co-operation eggs capable of re-
production are generated, and the continuation of the species is
secured. Such a sexually-mature, hermaphrodite joint of a
cestoid worm, which, in certain genera of Cestoidea, when fully
formed, separates from the body of the scolex with great
readiness, is denominated a Proglottis. The formation of these

Fig. 20. A scolex of Tcetiia from Avion empiricorum included within its receptacle.
Fig. 21. The same extruded, a. Head of the scolex. b. Receptaculum scolicis. c. The
remains of the six embryonic hooklets.

1 See the ' Zeitschrift fur Wiss. Zool.,' B. v, 1854, p. 383.

' I have found, not only in Breisgau, but also in Schleswig, and here in Bavaria, the
lung of the red slug {jJrion empiricorum) very frequently infested by the encysted
scolices referred to above; and I learn from Dr. Meissner that the same is the case with
ilie slugs found in the neighbourhood of Hanover.

FEEE JOINTS, OE PEOGLOTTIDES.

41

Proglottides takes place at the posterior end of the scolex by-
asexual reproduction; viz., by a simple process of growth and
division. If we compare this process with the phenomena of
the Alternation of Generations, we shall discover in it all the
essential characters of the latter. The matured joints, or the
sexual individuals, of the Cestoidea in their proglottis form, pro-
duce a brood of embryos armed with six booklets, which are
quite dissimilar in shape from their parents, the Proglottides, and
remain so, since at a later period they assume the scolex form,
and take on the functions of an agamozooid. From the posterior
end of the body of such a scoliciform agamozooid a series of joints
are developed; that is to say, a generation of sexual individuals,
which again present the original proglottis form. In their
organization, the Proglottides, apart from their sexual apparatus,
so far resemble the scolices, from which they have been pro-
duced, that they possess no oral aperture, and moreover are
subject to a deposit under their integument, of those glassy cal-
careous particles which I have already mentioned.

It seems, at first, paradoxical to say that the joints of a tape-
worm, which have hitherto been believed to be mere parts of one
animal, should be considered as individuals ; but whoever will
observe, with an unprejudiced eye, a fully developed Taenia with
its sexually matured joints, must be convinced that it is no
simple animal, but one composed of many individuals. The
joints of a Tcenia, when quite mature, become detached from one
another with the greatest ease ; the separated joints for a long
while preserve their form and remain quite fresh and lively,
being even capable of locomotion, and always seeking to dis-
burden themselves of their eggs before dying. Even the older
naturalists had regarded the single, separate joints of a Tcenia as
separate individuals, whilst others again, described the joints of
the common tape-M^orm of Man, [Taenia solium), as " Vermes
cucurbitini." Later helminthologists, however, rejected the idea
that a Tania was composed of ''Vermes cucurbitini," and especially
objected 1 to the view of Vallisnieri and Coulet,^ who maintained
that the TcenicB were produced by the mutual adherence of a
number of the cucurbitine worms into a complex, jointed whole.

' See his ' Considerazioni ert Esperienze intorno alia Generazione do' Vermi del Corpo
umano.' Padooa, 1710, p. 63.

' ' Tractatus de Ascaridibus et Lunibrico lato.' Lugduni Batavonim, 1729, pp 37
56, &c.

43

THE TAPE-WOEM.

Blumenbach stood almost alone among tlie later naturalists,
when, to the astonishment of his contemporaries, he defended
the incorrect vieAvs of Vallisnieri.^ The older inquirers were
quite right in regarding the various isolated Tcenia-joints as sepa-
rate individuals, though they certainly fell into a gross error in
imagining that the long, many-jointed Tania was composed of
coalesced Vermes cucurbitini • in point of fact it is exactly the
reverse, the Vermes cucurbitini owing their origin, to the break-
ing up of the Tania into separate joints. That the first impres-
sion of these old naturalists was a just one is evident, from the
circumstance that even modern helminthologists, meeting now
and then with solitary T(Enia-]omi^, with whose origin they were
unacquainted, have regarded them as peculiar individual worms,
and described them accordingly. A remarkable intestinal worm
described many years ago by Diesing, under the name of Thy-
sanosoma actinoides, which was foimd in the intestine of a species
of deer from Brazil, created much sensation amongst helmin-
thologists, until Diesing himself, not long ago, acknowledged
it to be an isolated joint or Proglottis of Tcsnia fimbriata?
Dujardin described the isolated joints of various Cestoidea as
forms of a peculiar genus of worms, to which he gave the name
of Proglottis.^ Although he believed them to be originally
derived from T(Sni(B, he was, notwithstanding, so firmly convinced
of their independent existence, that he made them into a sepa-
rate genus in his systematic arrangement of the Cestoidea.^
However, since more has been known of the alternation of gene-
rations, whereby the origin of one animal from another of quite
dissimilar form, and their mutual relations to each other have
been explained and familiarized, helminthologists generally admit
that a cestoid worm is really a colony of animals. How dif-
ficult naturalists formerly found it, to accede to a view that
since the time of Blumenbach had been a subject of ridicule,

' ' Gottingisclien Anzeigen von gelehrten Sacheii,' 1774, No. 154. Blumenbach
regards the anterior, smallest, joints of a tape-worm as the oldest, and he accounts for
their being smaller than tlie posterior joints by supposing that they have to give up the
nutriment which they take in, to their successors which have fastened on to them behind.
He compares these worms to the mass of authors, the more modern of whom merely
suck out of tlieir immediate predecessors, that which these had extracted in the sanie
way from still older writers.

- See his ' Systema Helrainthum,' i, 1850, p. 501.
' Annales des Sciences Naturelles,' t. xx, 1843, p. 341.

* ' Histoire Naturclle des Ilelminthes,' 1845, p. 630, ])]. 10. li^-s. a, n, c.

FREE JOINTS, OE PROGLOTTIDES.

is sho^yn by F. S. Leuckart, who, rightly appreciating the
true meaning of these jointed Cestodea, and yet apparently
not liking to oppose his contemporaries too strongly, merely
expressed himself thus upon the matter.^ " I was almost inclined
to consider the jointed tape-worms as organisms, in which each
joint is a separate animal, and the whole a compound animal, as
has been before supposed by many distinguished zoologists."
Steenstrup returned to the idea (loc. cit., p. 103) that the tape-
worms are compound animals, and subsequently, Van Beneden
in his admirable monograph, has pointed out and illustrated with
excellent figures many striking and conclusive examples of the
truth of the same view. In

looking at Coulet^s (1. c, figs. r~\^'^ -n

conception that these animal
bodies are independent exist-
ences. The separate joints (that is, the Proglottides,) of the
other species of Taenia are perfectly similar to these ; and the
Proglottides described by Van Beneden in the cestoid genera
Echeneibothrium, Phyllobothrium, Anthohothrium, Acanthobothriuni,
Onchobothrium, Calliobothrium,, and Tetrarhynchus, (all charac-
terised by clearly marked articulations), closely resemble them.

Since we must henceforward regard these Cestoidea as com-
pound animals, we may compare the many-jointed tape-worm
with a polypidom, although Ave must not forget that there are
some points of difference between the two. In the compound
polypes, the individuals bud out in various directions and relative
positions from their parent stock, whereby the polypidom, accord-
Fig. 22. Single and separated sexually mature joints of Tcenia solium (of the natural
size) with lateral sexual apertures, (*) and in different states of expansion and contrac-
tion (after Coulet). Each of these separate joints must be regarded as a sexual indi-
vidual of the Tcunia solium, and is the proglottis of this Cestoid worm.

' ' Versuch einer naturgeraassen Eiutheilung der Helminthen,' 1827, p. 21.

* ' Les Vers Cestoides,' 1850. It is to be regretted that Van Beneden has confined his
investigations to the scolices and proglottides, and has not examined the development of
the embryos.

3 — 16,) illustrations of the
separate joints {Proglottides)
of a Tania solitim in their
various states of contraction
and expansion, (fig. 22,) it is
impossible not to admit the

44

THE TAPE- WORM.

mg to its genus and species, receives a specific, ramified, folia-
ceous, or encrusting form, whilst in the compound tape-worms,
the individuals only grow out of the common stock in one
direction, and in a single series.

In the Cestoidea the stock is the posterior end of the scoliciform
agamozooid. In the alternation of generations amongst the
Cestoidea, there is this peculiarity, that the agamozooid preserves
its efficacy and independence, whilst the agamozooids of other
animals which undergo alternation either die after producing
their brood or pass into it.-^

We must consider the head of every cestoid worm as the
agamozooid still remaining and capable of reproduction, and its
neck as the equivalent of the posterior extremity of the scolex.
In all cestoids we see that fresh joints are continually being
developed at the posterior part of the neck, which lengthens
and becomes covered with transverse folds. These folds are at
first very close together, but as the process of growth throws
them backwards, fm-ther and further from their place of origin,
they gradually change from indistinct wrinkles into sharp trans-
verse lines of demarcation, between Avhich the substance of the
body dilates into a joint (individual), and assumes its specific
shape. At a later period, the rudiments of the hermaphrodite
sexual apparatus make their appearance in the interior of the
joints : and in proportion as the latter move backwards from their
parent stock (the neck), so much the nearer do they approach
to maturity, through progressive development of their sexual ap-
paratus ; and finally they separate themselves from their younger
fellows as independent individuals. I must not leave the fact
unmentioned that the formation of marked proglottidiform joints
does not take place in all Cestoidea. In the genera Tarda,
Tetrarhynchus and several others furnished with cephalic hooks
and suckers, the development and individualising of the pro-
glottides occurs in perfection. In the genus Bothriocephalus ,
although the joints exhibit a distinct demarcation, they show
little inclination to become separate. In Tricenophorus the
articulation is still less marked; whilst in Ligula it is obso-

' The correctness of this statement appears to be doubtful. Tlie stock of the
" Hydra tuba" remains after giving rise to a l)rood of Medmce, and neitlier dies nor
can be said to pass into the brood. The like is true of those Sertularida, Diphyd(S, and
PhysophoridcE which give rise to medusiform Zoiiids; nor does it seem to he otherwise in
the remarkable Trematode Gyrodactylus described by Von Siebold himself. — [Ed-]

OEiaiN OF THE PKOGLOTTIDES,

45

lescent, being only denoted by imperfect transverse folds on the
sides of the body. Here, in fact, many groups of hermaphrodite

Fig. 23.

sexual apparatus become developed close together, in the ribbon-
like body of the full-grown agamozooid, but the parts which
surround them do not break up into joints. In this respect
we may compare a Ligula, as a compound animal, with certain
polypidoms in which the individuals become, in a similar manner,
less distinctly separate from the parent stock.

For how long a time the head end of the cestoid worm can
play the part of an agamozooid, and how many sexual individuals
such a tape-worm can produce, has not yet been certainly proved.
The number of proglottides which a single scolex can bring forth.

Fig. 23. Kepresents, diagrammatically the metamorphosis of a Tetrarhynchiis into a
Rhynchobothrium (after Van Beneden, see also supra, fig. 19). a. A Tetrarhynchus
scolex, whose posterior extremity is growing and elongating, b. The elongated hinder
extremity exhibits transverse wrinkles which indicate the boundaries of the future
joints, c. The posterior end of the same scolex appears clearly jointed, i. e. provided
with proglottides. The Tetrarhynchus has thus become a Rhynchobothrium. a. One of
the four sucking disks, b. Protruded part of the four proboscides provided with
recurved hooks, c. Middle portion of the four proboscidean tubes, e. Unarticulated
portion of the body, e* Transversely wrinkled portion of the body, c** Articulated
part of the body giving rise to proglottides.

46

THE TAPE WOKM.

mustj in many species, be enormous, since many hundred articu-
lations may still be counted, in cestoid worms which have, for
months, been giving off numerous joints every day. Whether a
cestoid worm, after giving off a series of sexless individuals as
joints, can, after a certain interval of rest, repeat this process,
would be a difficult fact to determine either in man or in animals,
since it is impossible to be sure if the renewed production of
joints springs from one and the same agamozooid, or whether it
may not be the product of a more lately immigrated one.

THE CYSTIC ENTOZOA.

47

CHAPTEE III.

ON THE CYSTIC ENTOZOA.

Zoologists have hitherto founded the genera and species of
Cestoidea on the characters presented by the head and by the
fully developed joints only ; and even these characters have been
but superficially and imperfectly employed, so that a close
revision of this order of Entozoa has long been necessary. This
task has been recently undertaken by Diesing and by Van
Beneden, but the labours of these two helminthologists have led
them to very different results. The great point in revising the
old genera and species of the Cestoidea is, to discover what forms
of proglottis belong to certain scolices which are commonly found
without proglottides (and which, therefore, have long been
regarded as distinct genera of Cestoidea), and to unite these
together, Diesing has not attempted to do this, having appa-
rently no conception of the bearing of the alternation of gene-
rations upon the systematic arrangement of the lower animals.

On the other hand, Van Beneden, guided by the light of the
alternation theory, has justly recognised and given due promi-
nence to, the affinities of certain Cestoidea. To this end the
different kinds of scolex require to be more carefully defined
than they have hitherto been, and the use of the microscope
becomes indispensable. The forms of the apparatus of attachment
must be determined and compared with the utmost care, and
those hooks and protractile proboscides, armed with more or less
moveable booklets, which are attached to the head of the scolices,
are especially adapted, from their varying and well marked figure
and disposition, to afford good generic and specific characters.
If the form and arrangement of that apparatus of attachment of
the TcBniadoi which is known as the circlet of hooks, of the
proboscis which carries it, and of the sac which conceals it, had
been carefully observed, the identity of many so-called species of
Taniadce would long since have been recognised, and the close

48

THE CYSTIC ENTOZOA.

relation of tlie Cystica with the Cestoidea would not have been a
recent discovery. It must not be forgotten, however, that in
very many Tceniadce, the scolices lose their circlet of hooks with
advancing age, and that in many Cestoidea, the suckers of the
scolices undergo great changes of form when the development
of proglottides commences ; in consequence of M'hich it is often
very difficult to demonstrate the connection of the older and
younger individuals of one and the same species of cestoid.
The proglottides of the Cestoidea, again, considered as individuals
whoUy separate from the parental organism, present distinct
specific characters, though they are not, perhaps, very obvious
at first sight. In these it is the sexual apparatus more par-
ticularly which, forming as it does the principal mass of the
proglottis, presents excellent specific characters, in the form,
dimensions, number, and arrangement of its parts. Van Beneden
has the merit of having paid particular attention to these par-
ticulars in distinguishing the different species of proglottis.

As I have already hinted, the cystic worms, which were made
by Rudolphi into a distinct order of Entozoa, are so closely
allied to the Cestoidea that they have no claim whatever to be
regarded as an independent group. Since, in addition, various
kinds of scolices have been regarded as distinct genera of
Cestoidea, it is high time that zoologists should resolve to erase
from their systematic arrangements all these groups, which are
in reality, based only on our ignorance of the natural history of
the Entozoa. How great a number of these improper genera
have been introduced may be judged by the fact that out of the
order Entozoa cephalocotylea, alone, established by Diesing/ and
containing thirty-two genera, ten genera must be eliminated,
namely, Echino coccus, Cosnurus, Cysticercus, Piestocystis, Antho-
cephalus, Acanthorhynchus, Pterobothrium, TetrabothriorMjnchus,
Stenobothrium, Scolex. Many of the Entozoa arranged under
these genera are merely the scoliciform agamozooids of other
Cestoidea ; a fact which is demonstrated not merely by their
undeveloped and sexless body, but by their habitation, since they
are almost all found, not in the alimentary canal of a vertebrate
animal, but in its other viscera. Another portion of these genera
consists of the cystic worms, which arc also nothing but the
scolices of certain Cestoidea, with this difference, however, that a
portion of their body is enlarged into a vesicle.

' Diesiiig, ' Systeina Heliuinthum,' i, p. 478.

THE CYSTIC ENTOZOA.

49

To prove tliat the cystic Entozoa are the sexless and va-
riously degenerated nurses of the Cestoidea, I must once again
return to the already mentioned (page 36) development of the
cestoid agamozooids. When the cestoid embryo has immigrated
and established itself in any organ of an animal, it begins to
develop a scolex by internal budding, which takes the form of a
7<ewia-head or of a Teirarhynchus-head, &c., according to the
origin of the embryo. The embryo then increases and becomes
enlarged by the growth of the scolex, which it holds enclosed
within the distended walls of its body. These walls pass inter-
nally into the neck of the scolex, directly over the spot whence
the scolex sprung. On the external surface a funnel-shaped but
narrow depression is developed opposite the scolex, from which
a canal stretches through the neck of the scolex to its head.
This canal, after the full development of the scolex, permits its
evolution, by which means the hinder end of the scolex passes
immediately into the body of the embryo. The fully developed
scolex in the interior of the embryo appears as if it had drawn
itself inwards by a process of involution ; but observatioia teaches
us that the scolex is originally developed in this involuted con-
dition, instead of becoming retracted when it has attained its full
development. The material required for the development of
the scolex and of the embryo which invests it, is taken up by
the latter by absorption through its integument. This absorptive
power of the integument may vary in amount, and produce
different results, which are, of course, dependent upon the
quantity and quality of the fluids, and upon the special pecu-
liarities of the organs of the animal in which the embryo has
taken up its residence. Under particular circumstances it may
easily happen that an embryo should absorb, through the surface
of its integuments, more nutritive fluid than is necessary for the
growth and development of the scolex. The surplus nourish-
ment then gives rise to exuberance of growth and to degenera-
tion of the body of the embryo. The immediate consequence of
the accumulation of absorbed and unemployed nourishing juices
will be a vesicular enlargement of the embryonic body ; and the
cestoid embryo in this condition has received the name of a
cystic worm. The development of the scolices in such cystic
entozoa is sometimes more, sometimes less, advanced. .

I have already shown that the cestoid embryos, after leaving
their eggs, must wander, in order to establish themselves in

4

50

HYDliOPIC DEGENERATJON.

fitting animals and become developed into agamozooids. If any-
thing is to come of these wanderings, however — that is to say, if
the cestoid embryos are to propagate, two main conditions must
be fulfilled. In the first place, the localities chosen for lodge-
ment must afford suitable nourishment; in the second place,
the animal selected by the embryo as its home must afford an
opportunity to the scolex developed within it, to reach the
appointed intestinal canal of a vertebrate animal, either by active
or passive emigration, in order to accomplish its sexual development
and propagation. That the cestoid embryos should often go far
astray in their wanderings, whereby these conditions are left unful-
filled, is easily conceivable ; however, these strayed cestoid embryos
do not perish, but notwithstanding the degeneration which they un-
dergo retain sufficient tenacity of life to be capable of further
development and propagation. Objections have been raised by
some to the opinion I have just expressed, that strayed cestoid
agamozooids may undergo dropsical degeneration ; and it is urged,
on the contrary, that the vesicles of these hydropic scolices are a
necessary organ, a sort of reservoir of nutriment. In answer to
this, I can only repeat what I have already said in another place,^
in vindication of my views, viz., that I cannot see why one should
deny the possibility of a degeneration in form among worms,
since it is observed in the higher animals, where the modifi-
cations produced by climatic influences and change of food are at
once admitted as " Races.^^ If, in many of these races, an extra-
ordinarily luxuriant growth of hair shoots out over the whole
body, or on various parts of it; if the horns of certain races of
ruminants have the property of lengthening, or even of doubling ;
if the ears of certain kinds of our domesticated animals become
disproportionately long and drooping; if, in some races, local
fatty degeneration takes place in the shape of a fatty tail or
hump, why should not an accumulation of serous fluid in certain
parts of the body, giving rise to a local dropsy, take place
amongst the lower orders of animals, when these are exposed to
the influences of an unusual mode of life ?

The processes of degeneration to which the cestoid embryos
are liable in their wanderings are of two different kinds ; either
the body of an embryo lengthens posteriorly into a solid caudal
appendage, or else it becomes distended into a watery vesicle by

' ' Zeitschrift fiir Wiss. Zoologie,' Bd. iv, 1853, p. 407.

THE CYSTIC ENTOZOA.

51

the accumulation of serous fluid. It may even happen that both
these forms of degeneration attack the same embryo. For the
better comprehension of these occurrences of excessive growth
and of degeneration in the coiu-se of the development of the
cestoid embryo, I ^vill distinguish the part of the body of the
embryo which becomes distended by the formation of the scolex,
by the name of the receptaculum scolicis. Strictly speaking, this
receptacle is no other than the embryo itself (see page 37, fig. 19**).

Whilst the scolex is becoming developed within the receptacle
of a cestoid embryo, many and various changes of form may
be going on in the embryo itself, pari passu with the vesicular
change, and these have given occasion to the erection of the
various genera of cystic Entozoa.

Those Tsenioid embryos whose receptacle has become dis-
tended to sometimes a larger, sometimes a smaller vesicle, have
been hitherto included in the cystic genus Cysticercus. If such
a Tcenia scolex extrudes itself from its vesicular receptacle^ it is
obvious that the posterior part of the scolex passes immediately
into the vesicle, and the presence of such a caudal vesicle in the
scolex of a Tcenia has been raised into the generic character of
the Cysticerci (figs. 24, 25). Exposed to certain external in-
fluences, the receptacle of a Tcenia

scolex becomes distended into a very Fig. 24. Fig. 25.

large and spacious vesicle, from the
inner surface of which, a number of
Tamia scolices develop by budding; I
this form of cystic worm has been /
elevated into a genus, Coenurus. An-
other kind of Taenioid embryo becomes
metamorphosed into a vesicle of larger
or smaller dimensions, from whose inner siirface countless scolices
pullulate ; these, however, become detached, and lie freely within
the cavity of the closed parental vesicle. Upon this form the
genus Echinococcus has been founded.

Fig. 24. Ci/sHcercics cellulosep. from the human brain, of its natural size, and with
a retracted anterior extremity. Fig. 25. The same Cysticercus extruded, a. The caudal
vesicle of the Cysticercus, which is nothing hut the receptaculum scolicis (or hinder end
of a Taenioid emhryo), distended into a vesicle by the accumulation of water, d. The
retracted anterior end of the body of the Cysticercus contains the taenioid scolex dove-
loped by budding within the embryo, c. The transversely wrinkled anterior extremity
of the Cysticercus. d. Its head and neck, which conjointly form the Tajnioid scolex.

CAUDAL APPENDAGES.

The changes of those cestoid embiyos in which the receptacle
grows out behind into a long, solid, caudal appendage, are very
remarkable. The receptacle of the Tania scolex which Stein
observed in the meal-worms, developes such an appendage (page
38). I must remark here, that Stein considers the scolex recep-
tacle as a cyst, and the caudal appendage as a part of it, Avhich
is certainly not correct, for if the tail does not appertain to the
embryo, how could the six hooks have come to lie upon the
upper surface of the tail, where, according to Stein's express
assertion, he invariably saw them ?

The Piestocystis crispa, which attains a length
Fig. 26. of from one to three inches, is nothing more than
a Tcenia scolex evolved from its receptacle, with a
very long, ribbon-like, solid, caudal appendage.^ In
certain Tetrarhynclii the receptacle also becomes dis-
tended into a vesicle, and such forms of Tetrarhynchi
were united by the older helminthologists into the
genus Anthocephalus. From this genus Diesing
separated, under the names of Acanthorhynchus and
PternboUiium, ila.o^e,Tetrarhynchus scolices, the pos-
terior end of whose receptacle is produced into a
very long, unjointed, caudal appendage. As in
these degenerations, the form and size of the vesi-
cular dilatations of the receptacle, as well as the
shape and length of its caudal appendage, are often
dependent upon accidental external influences, the
dissimilarity which the parts present in different individuals of
one and the same species of scolex become readily intelligible.
For this reason, such diagnostic characters of genera and species
as are derived from the conformation of the vesicular enlarge-
ments and of the caudal appendages of the receptacle must be dis-
carded on account of their uncertainty. Only on the form of
the scolex (the so-called head of the sexually matured cestoids) is
it possible to base constant generic and specific characters. A

Fig. 26. A Tcenia scolex from the meal-worm retracted within its receptacle ;
partly after Stein, a. Head of the scolex. b. Receptaculum scolicis. c. Caudal
appendage of this receptacle, on which lie scattered the six embryonic hooks.

' This animal was formerly described by Riidolphi as Cysticercm crispus. I have
demonstrated, however, in the ' Zeitschrift fiir Wissenchaftliche Zoologie,' (Bd. ii, 1850,
p 223), that this worm possesses no caudal vesicle.

THE CYSTIC ENTOZOA.

53

striking proof of this is offered by the Cysiicercus cellulosoi, of
which the diagnosis invariably states, that it possesses a " vesica
caudalis, elliptica, transversa." This form of caudal vesicle is,

however, only found in. such Cys-
Fig. 27. Fig. 28. ticerci as are imbedded in the mus-

cles of men and pigs ; in individuals
of the same species residing within
the human brain, the caudal vesicle
assumes the most various and irre-
gular forms (figs. 24, 27, 28). Even
in the Taenia- scolex observed by Stein,^ the caudal appendage
of the receptacle assumed the greatest variety of shapes.

If attention had been earlier directed to these circumstances,
the cystic Entozoa would not have been made into a separate
order from the Cestoidea. The older naturalists and helmin-
thologists took a far more just and unprejudiced view of the
matter, when, from the similarity of the degenerated cystic
scolices with the heads of certain Cestoidea, they divined the
close connection of the two orders, and described the Cystica as
Tcenia vesicularis, Taenia hydatigena, Taenia cellulosce. Even the
dropsical condition of these cystic worms did not escape the eyes
of the older naturalists, since already, in 1691, Tyson^ described
the Cysticercus tenuicollis as Lumbricus hydropicus.

But after Linneeus had animated naturalists with his spirit of
arrangement, they worked with such good will and so exclusively,
at the perfection and completion of his system, that for a long
time it seemed to be thought enough if generic and specific
names were given to newly discovered animals, and their due
systematic place assigned. The inquiry into the natural history
of these animals hence became quite a secondary consideration,
and with such a one-sided study of animal forms, it could hardly
fail to happen that not merely varieties, but also young states,
larvjE, and even fragments of animals already known, should be
described and systematically arranged as peculiar animals.*''

Figs. 27, 28. Two Cysticcrci rendered quite irregular by constriction of their
vesicles ; from the human brain, natural size. b. The retracted anterior edge of the
scolex. In fig. 28 the constricted parts are produced into tubes.

' See ' Zeitschrift fur Wiss. Zoologie,' Bd. iv, 1853, p. 207, and pi. x, figs. 12—14.

' ' Philosophical Transactions,' 1691, No. 193, p. 506, figs. 1 4.

' Ehrenberg's and Diesing's systematic works on Infusoria and Entozoa, testify that
this faulty and one-sided method finds followers even now.

54

CYSTICERCUS FASCIOLAEIS.

It is to the peculiarity in the form of the Cysiicercus fascio-
laris that we owe the recent recognition of the connection
between the cystic and the cestoid worms. The similarity of the
head of this Cysiicercus with that of the Tcenia crassicollis is so
great and striking, that I can scarcely claim much merit for
having been the first to entertain the idea which I thus ex-
pressed ■} the Cysiicercus fasciolaris is nothing more than a
strayed or degenerated Taenia, which may, however, attain the
normal form of a tape-worm if transported to the intestinal
canal of a suitable animal. Both forms are so intimately related
to each other in form and organization, that I am not surprised
at Allen Thomson, of Glasgow, having recognised the agreement
of the Cysiicercus fasciolaris with the Tcenia crassicollis without,
as it seems, being aware of my researches and publications upon
the subject.^ The mutual affinities and relations of these two
Eniozoa are the more perceptible, because during the growth of
the Cysiicercus fasciolaris the joints of the future tape-worm are
developed between the caudal vesicle and the head. These joints
certainly remain narrow, and develop no sexual apparatus, but
they give to the scolex, which in this stage of development
always has the head extruded, such a characteristic appearance,
that its identity Avith the Tcenia crassicollis can only be denied by
those who regard the caudal vesicle as the sole test of sys-
tematic position. If we examine the Cysiicercus fasciolaris or
altered Tcenia crassicollis, more narrowly, we shall perceive in this
tape- worm the same peculiarity which occurs in the various other
cestoids, for instance, in Tricenopliorus nodulosus, Tcenia longicollis
and ocellata, viz., that the body of the tape-worm grows from
the back part of the head and neck of the scolex, even before
this has reached the intestine of the vertebrate animal adapted to
its sexual development (see page 32). There is, however, an
additional departure from the ordinary course in the Tcenia cras-
sicollis, that during the development of its scolex its receptacle
undergoes a dropsical degeneration.

As the Cysiicercus fasciolaris, which is found always encysted,
in the livers of various rodents — most commonly those of rats
and mice — is often met with several inches long, the caudal
vesicle terminating the elongated body of such individuals, which

' Compare my article " Parasiten," 1. c, pp. 650, 676.
< Zeitschrift fiir Wiss. Zoologie,' Bd. iii, 1851, p. 97.

THE CYSTIC ENTOZOA.

55

never grows in the same proportion, is very minute, which seems
to render probable the notion that the candal vesicle of these
cestoids has not originally been a scolex receptacle, but is rather
the hinder end of the tape- worm in a diseased and dropsical
state. Such dropsical enlargements are undoubtedly found occa-
sionally in single joints of the Cestoidea ; but if attention is paid
to the gradual development of the tsenioid Cysticercus fasciolaris
it will be seen that its caudal vesicle is at an early period a true
recepiacuhim scolicis. I have before me many examples of the
Cysticercus fasciolaris which present the most various stages of
development, the oldest being from five to seven inches long,
whilst the youngest were no more than from one to four lines.
Amongst the older individuals the long body is distinctly jointed ;
in the younger the short body merely presents very close trans-
verse wrinkles as indications of the future joints. At all these
difierent ages, the caudal vesicle appears to have about the same
size, and indeed in the older individuals is even somewhat smaller.
The youngest individuals, of one and one and a half lines long,
have no body at all ; in these the head and neck of the scolex
only project, in the slightest degree, from the vesicular recep-
tacle, whilst these parts, in the smallest individuals, which possess
a perfectly rounded vesicle, are still, as I have most distinctly
convinced myself, concealed in the receptacle. If one were care-
fully to inspect the livers of many difierent species of murine
rodents, one would certainly come upon still younger forms of
development of the scolex of Tcenia crassicollis ; one might even
be so fortunate as to discover the embryo hooks on the external
surface of the receptacle of the developing scolex, although the
discovery of these six hooks of the cestoid embryo, on account of
their excessively small size, is a very difficult task. In the Cys-
ticercus pisiformis, which, always encysted, infests the livers of
hares and rabbits, I have succeeded in meeting with the scolex
receptacle, in a very early period of development, with a diameter
of half a line. The internal gemmation had just begun, the four
suckers of the future scolex were scarcely sketched out, and the
still soft apices of the circlet of hooks were only just in process
of formation (see fig. 33, d, e), but I sought in vain for the six
embryo-hooks on the external surface of the receptacle. In
pursuing these inquiries, however, a very interesting phenomenon
was presented by the livers of some wild rabbits of this neighbour-

56

CYSTICEECUS PISIFOEMTS.

hood. Besides containing many very small scolices of Cysti-
cercus pisiformis just developing, there were a number of short,
pale-yellow lines crossing each other in all directions, which, upon
microscopical inspection, did not seem to be sharply defined, and
appeared to consist of a granular substance. I suspect that this
substance was the product of an exudative process, occasioned
by the creeping about of the immigrated T^ema-embryos in the
substance of the liver ; probably it would be gradually reabsorbed
when, in course of their development and metamorphosis, these
embryos had become converted into the dropsical receptacles of
Cysticercus pisiformis.

CHAPTER IV.

ON THE ORIGIN OF THE CESTOID AND CYSTIC ENTOZOA.

The extraordinary likeness of tlie Cysticercus fasciolaris of
rats and mice with the Tania crassicollis of cats^ and the fact
that the above rodents are the principal food of cats, and that,
moreover, the joints of the Cysticercus fasciolaris enclosed in the
cysts in the livers of rats and mice are never sexually developed,
inclined me to believe that this sexless Cysticercus fasciolaris
would be changed into a sexually matured Tania crassicollis, as
soon as the animal it lodged in should be devoured by a cat.
For, under these circumstances, the liver of the devoured rodent
would be digested in the cat^s stomach, and the cystic worm,
freed from its cyst, would be transplanted to a place where, after
casting off its caudal vesicle, it might, as a Tania crassicollis,
attain to sexual maturity in the intestine of the cat. Fully as I
was persuaded of the possibility of such a transformation of the
Cysticercus fasciolaris into Tania crassicollis, yet I could hardly
conceive that the other species of Cysticercus, in which no jointed
body was developed between the head and caudal vesicle of the
scolex, could become Tania ; and this appeared the more un-
likely, as I had often found cysts that had perished, in which the
Cysticerci they contained were dead, and lay shrunk and buried
amidst inorganic calcareous deposits. Such a calcareous de-
generation of the cysts-^ must assuredly render the cestoid scolices
incapable of propagation ; still all do not meet with this fate, for
under favorable circumstances they can, even in spite of their
dropsical receptacle, subserve the multiplication of sexual cestoids ;
that is to say, when they are transported into the intestinal canal
of animals fitted for the development of Proglottides.

That the cystic Entozoa can thus become changed into sexual

' I have more particularly described this process in the ' Zeitscrift fur Wissenschaft-
liche Zoologle,' Bd. ii, 1850, p. 225.

58

FEEDING EXPERIMENTS.

cestoids, has been proved by Kiichenmeister, of Zittau, by experi-
ments first made by him, and published in various medical and
natural history periodicals.^ It was a very happy thought of his
to mstitute experiments of feeding animals with Cysiicerci. I
have repeated and extended these feeding experiments, and can
substantiate what Kiichenmeister was the first to make known,
viz., that certain cystic Entozoa become TcBnice in the intestinal
canal of dogs.

The chief condition for the success of these experiments is, that
the cystic worms should be lively, or at least capable of being
revived when administered ; to which end they must be made use
of directly, or at the most a few hours after, the death of those
animals which yield them. As long as the organs of the mam-
mals in which these parasites abound remain warm, one may be
sure that the worms are still living ; with the cooHng of the
infested organism, they become gradually languid, and at last
seem quite dead, but from this state they can be restored to
life, even after the lapse of several hours, by the application of
warmth. When I was not certain whether the cystic worms
I was using for my feeding experiments were still living or not,
I threw them into luke-warm water, and then only made use of
those individuals which had by this means been re-animated.

To produce tsenioid worms out of cystic worms, I caused the
latter to migrate passively into the intestinal canal of puppies by
feeding these with them. Puppies of about a week or two old
were most suitable. They lapped up the milk in which the
cystic worms were mixed very readily ; those which exhibited no
particular appetite at the moment had their jaws held open and
the milk poui'ed down their throats, so that the swallowing of the
worms was secured. At first I made use of cats, rabbits, and
Guinea-pigs, also, for these experiments ; but they afibrded me no
satisfactory results.^ But the dog, as I shall presently show, is
by his mode of life naturally obnoxious to those cystic worms
with which I experimented, and hence the experiments with
puppies necessarily succeeded.

' The first notice is given in Giinsburg's ' Zeitsclirift fiir Klinisclie Vortriige,' 1851,
p. 240.

* All the feeding experiments cited in the following pages were carried on in the year
1852.

OEIGIN OF CYSTICA AND CESTOIDEA.

59

1. EXPERIMENTS OP FEEDING WITH CYSTICERCUS PISIFORMIS.

The cystic entozoon, known by the name of Cysticercus
pisifo/ mis, is a very common inhabitant of the liver and peritoneum
of hares and rabbits. Cysts as large as a hazel-nut are frequently
disseminated completely through the substance of the liver of
haresj and these cysts are not unfrequently found hanging down
like bunches of grapes from the external surface of the liver ; in
rabbits the great omentum and the mesentery are generally full
of these cysts. Commonly such a cyst only contains a single
Cysticercus pisiformis ; but two are also sometimes enclosed in a
common cyst. In Breslau^ the rabbits which were sold in the
markets in the spring months of 1852 were almost invariably
infested by this Cysticercus, whence I made use of them at the
Physiological Institution in that place for my feeding experiments.
The results of these experiments were published in the inaugural
dissertation^ of my pupil^ Dr, Lewald, who took a yery active share
in them ; subsequently I gave some account of them myself in the
' Zeitschift fiir Wissenschaftliche Zoologie/ Bd. iv, 1853. The
number of Cysticerci which I administered at once in these experi-
ments was various, seven, twenty, forty, and sixty. In all cases,
the Cysticerci were left enclosed within their cysts, and in these
experiments, as in all subsequent ones, I wrote down in my
journal, the precise time of feeding, the number of the cystic
worms made use of, and the dogs fed with them, subjecting these
last, after feeding, to strict watching and careful attention.

.Of experiments tried with Cysticercus pisiformis upon ten
dogs, the following are the results, which I repeat from the report
I made in my essay in the Zeitschift cited above. When the
encysted Cysticerci are devoured, it is the cysts which are first
attacked by the gastric juice in the dog's stomach, and then the
caudal vesicle is consumed ; but not, however, the remaining part
of the Cysticercus, so that of the whole Cysticercus pisiformis
nothing more is left than the whitish round body which was
enclosed in the caudal vesicle, and which consists of the head and
neck of the animal involuted within its body, or, in other words,

' This dissertation appeared at Berlin in 1852, under the title 'De Cysticercorum in
Taenias metamorpliosi pascendi expcrimentis in institute physiologico Vratislavensi
administratis illustrata.'

60 FEEDING WITH CYSTICERCUS PISIFOEMIS.

is the scolex. Even before the caudal vesicle is digested, it fre-
quently shrinks and collapses, its thin contents being discharged,
probably by exosmosis, into the thicker fluid of the stomach!
Accompanying the latter, the remaining portions of the Cysticerci,
VIZ., the tailless bodies with their involuted neck and head, pass
into the duodenum through the pylorus. Having reached the
duodenum, the heads and necks of the Cysticerci are extruded,
in order that they may find places of attachment by means of
their suckers and hooks, between the villi of the intestine, where
they may await the growth and further development of the
other parts of their body.

During the first hours of their sojourn in the small intestine,
these outstretched tailless Cysticerci (scolices) often present a
bloated oedematous appearance ; but by degrees the body becomes
thinner, probably parting by exosmosis with its superabundance
of fiuid, and in this manner establishing an equilibrium with
the more or less viscous chyle. In all these Cysticerci the
posterior end is clearly the place where, at an earlier period,
the caudal vesicle was attached, as is evinced by a sort of scar,
like a notch or incision, from which at first very delicate
flakes of membrane depend, the remains of the digested caudal
vesicle. Already, after a day or two, the worms begin to exhibit
a growth, in which only the body takes part, the neck and head
being already fully developed, whilst the worms were still within the
peritoneum of the rabbits. Whilst the bodies of the worms, as yet
unjointed, and only provided with very close transverse wrinkles,
increase in length, the transverse wrinkles also multiply ; and if
the growth of the body goes on uninterruptedly, the transverse
wrinkles, after a day or two, change by degrees into distinctly
marked articulations ; the joints, which are at first very short,
lengthen, and there appears either on the one lateral border or on
the other a kind of papillose elevation, which afterwards becomes the
aperture of the sexual organs. In this condition the ingested
worms have exactly the appearance of a Tcenia, and only betray
their origin by that scar on the terminal joint of their body, of
which I have already spoken. After remaining tAventy-five days
in the dog's intestine they have become TcenicB, of from ten to
twelve inches long. The growth of these Tanice goes on without
intermission, the posterior joints increasing in size, and the re-
productive organs in the interior developing more and more,
whilst at the hinder limit of the neck fresh joints are continually

OETGIN OF CYSTICA AND CESTOIDEA.

61

produced from the transversely wrinkled anterior part of the body.
In tkree months these Tcenia attain the length of from twenty
to thirty inches and more.^ In such Tcenice the posterior joints
seem to have reached their full sexual development. In some of
these tape-worms the last joints become cast off, a proof of their
having attained their sexual maturity. The eggs contained in
the fully formed joints, are perfectly developed^ and contain an
embryo, furnished, in the usual manner, with six moveable hooks.

After having thus obtained sexually developed Tania, that is
to say scolices with sexually matured jn'oglottides, from the
Cysticercus pisiformis, I was enabled to decide to which species
of tape-worm these scolices, as the head end, and the proglottides,
as joints, belonged, and I recognised in them the Tania serrata,
which had long been known to infest the intestine of dogs. The
form of the head, the number, shape, and arrangement of the
hooks encircling the head, the construction of the joints, and of
the sexual organs within them, the form of the developed eggs,
all persuaded me that I had educed the Taenia serraia out of the
Cysticercus pisiformis.

Perhaps some of my readers may doubt the conclusion I drew
from the above-mentioned experiments, and may object — How
could I be sure that the dogs which I fed with the Cysticerci
might not have come by the tape-worms known as Tcenia serrata
in some other manner ? This objection occurred to myself, and
all the more strongly since in searching the intestinal canal
of dogs fed with Cysticercus pisiformis I often met with
thread-worms and tape-worms of another kind [Tcenia cucume-
rina), among individuals of T<£nia serrata. So that the question
naturally arose whether, in the same way as individuals of the
dog's thread-worm [Ascaris marginata), and the ordinary dog's
tape-worm {Tcenia cucumerina), had found their way into the
mtestine of the dogs experimented upon, so these individuals
of the other rarer tape-worm [Tcenia serrata) might not also have
arrived there without any assistance of mine. I can, however,
brmg forward the following demonstrative evidence to substantiate
my assertion, that the individuals of Tcenia serrata which I dis-
covered in the course of these experiments were really produced
from Cysticercus pisiformis. I have repeatedly searched the

' With regard to these different stages of development, see the figures in Lcwald's
' Dissertation,' cited above.

62 FEEDING WITH CYSTICERCUS TENUICOLLIS.

intestines of puppies of the same litter as those I had used in
my other experiments, and have never found Tcenia serrata in
them ; but, on the other hand, I have very commonly met with
Ascaris marginata and Taenia cucumerina. I must here remark
that I only made use of parlour and house dogs for my purpose,
and it is in these that both the above-named parasites ordinarily
appear, the Tania serrata more commonly infesting hunting dogs.
Still further confirmation of my view is afforded by the impor-
tant circumstance that after feeding the dogs with Cysiicercus
pisiformis, the number of tape-worms of the species Tania
serrata, which were found more or less developed in their digestive
canal, agreed exactly with the number of Cysticerci I had given.
Another circumstance worthy of observation, and strongly con-
firmatory of my view, is, that the size and the condition of
development of the Ttsnia serrata in the intestine of the dogs
that had been fed with Cysticerci, exactly corresponded with the
time that had elapsed since the period of feeding.

2. EXPERIMENTS OF FEEDING WITH CYSTICERCUS TENUICOLLIS.

The slender-necked Cysticercus is very commonly met with in
the viscera of our fat cattle ; as regards its caudal vesicle it is the
largest of all the Cysticerci, for this often attains to the size of a
fist, whilst its head never exceeds that of an ordinary Cysticercus
in circumference. As these Cysticerci were generally brought
to me enclosed in their cysts, and as the walls of the cysts were
penetrated by a great deal of fat, I ahvays disengaged the tape-
worms from their investments before I fed the dogs with them.

First experiment. — In the beginning of May, 1852, I made my
first preliminary experiment of feeding with iheCysticet'cus tenuicollis
upon a young hound ten weeks old, to whom I gave six Cysticei'ci
within four days. A few days afterwards I found, in this dog's
intestine, only the head ends of the ingested worms. They were
from one to one and a quarter line in length, and consisted of
the head and solid neck of the former cystic worm, of which the
scolex had alone escaped digestion. In order to ensure the
greater success of my experiments, I each time cut off before-
hand the voluminous caudal vesicle of the selected tape-worms,
and only fed the dog with those which had the neck and head
involuted in the cylindrical and hollow body.

Second experiment. — On the 11th May, a second young hound

OEIGIN OF CYSTICA AND CESTOIDEA.

63

was fed with twenty-one cystic worms. On the 12th May, he
had five, and on the 14th, three more, so that this dog altogether
swallowed twenty-nine Cysticerci without their caudal vesicles.
On examining the dog on the 17th May, seventeen scolices were
found in his small intestine, of which the smallest was from three
quarters to one line in length, and the largest two lines.

Third experiment. — A young poodle swallowed, on the 18th
June, twelve Cysticerci, of which, on the 23d of June, eleven
were found as scolices, from one to two and a half lines in length,
in the small intestine of the dead animal.

It was then the body of the Cijsiicercus that had perished by
digestion, for the short thick body of these scolices was no other
than the neck of the Cysticercus. It showed no trace of trans-
verse wrinkles, and at its posterior end appeared to be cut off
transversely or obliquely, with a sort of hollow scar in the
middle, denoting the place where the hollow cylindrical body of
the Cysticercus had been detached in the dog^s stomach.

In uninjm^ed individuals of Cysticercus tenuicollis one can
easily recognise that portion of the body which, in the small
intestine of the dog, becomes the scolex, by putting the uninjured
worms into lukewarm water. The worms seem to like the
warmth, which corresponds with that of the mammals they infest,
moving about in the most lively manner, and stretching out their
tubular body (previously contracted into a short, transversely
wrinkled, milk-white knot), with the head seated at its extremity
on a short, slender, and solid neck, for a long distance. This thin
neck appears to be sharply separated from the body of the worm,
and easily permits the line of demarcation to be seen, where, at
a later period, the head and neck become detached as the scolex.^

Fourth experiment. — A young mongrel pug-dog received, at
various intervals, two- and-twenty cystic worms; namely, on the
11th July, six; on the 14th July, fourteen; and on the 17th,
two. The examination of this dog when killed, on the 5th
August, proved that out of these two-and-twenty worms nineteen
individuals had passed as scolices out of the stomach into the
small intestine, and that their seventeen to three-and- twenty
days' sojourn had caused a remarkable growth in their abdominal

' Amongst the various figures of the Cysticercus tenuicollis, that given by Pallas,
(see his 'Miscellanea Zoologica,' 1766, p. 167, Tab. xii, fig. 10; or ' Stralsundisches
Magazin,' Bd. i, 1767, p. 69, Taf. ii, fig. 10), exhibits the head and neck marked off
from the body of the worm as the future scolex, very distinctly.

64 FEEDING WITH CYSTICEECUS TENUICOLLIS.

end which gave them the appearance of tape-worms. The length
of these tape-worms varied with the difference of age from four
lines to an inch and three quarters. The shortest individuals
evidently proceeded from those scolices which had been only
seventeen days in the small intestine of the dog.

In the individuals of four lines long one could trace very close
transverse wrinkles gradually appearing behind the neck, always
more closely defined towards the posterior part, and denoting,
where they became wider apart, the future joints of this portion
of the body. The individuals of eight lines long, already
possessed a clearly jointed hinder end, the joints increasing
in number with the length of the individual. In all the indi-
viduals the scar I have mentioned was to be seen on the hinder
extremity of the body, or on its last joint. This last joint with
the scar, moreover, always appeared smaller and more slender
than the preceding ones, from which it follows that it is in that
part of the scolex which is situated between the posterior end
and the neck that the growth and articulation of the tape- worm
takes place. The sexual apparatus was not perceptible either in
the interior or on the exterior of the joints of these tape-worms
of from seventeen to twenty-tliree days old.

Fifih experiment. — On the 19th July, eight Cysticerci were
given to a sporting dog, and on the following day six-and-twenty,
to which were added four more on the 22d ; so that within four
days this dog had devoured altogether eight-and-thirty Cysticerci
tenuicolles. The small intestine of this dog, which was inspected
on the 20th August, afforded tliirty-t^A'o Tanice in very different
stages of development. In regard to their length, a great differ-
ence already prevailed ; in the smallest individuals the diameter
varied from four lines and a half to one inch and a half, whilst
the longest extended from five to ten and a half inches. The
consequence of this was that although from nine-and-twenty to
two-and- thirty days had elapsed since the Cysticerci had been
administered, their scolices had most unequally developed, some
of them being greatly behindhand in point of growth. I ob-
served the same thing in several other experiments. The reason
of this unequal development of the tape-worms may lie partly
in the different individuality of the Cysticerci, partly in that
of the dogs fed with them. In the longest individuals that I
obtained from this experiment the development of the joints was,
moreover, most advanced; although these joints were always

OEIGIN OF CYSTICA AND CESTOIDEA.

65

wider than they were long, still the development of the sexual
apparatus, manifested externally by the presence of irregularly
alternating sexual apertures on one side or the other, had already
commenced within them. In a few of the most developed pos-
terior joints of one individual, I could perceive roundish hard-
shelled eggs, which contained the characteristic embryo with six
hooks, and in regard to shape, size, number, and arrangement
of the investments of the egg, exactly resembled the eggs of
the Tarda strrata. I must also remark, that in the larger indi-
viduals the developed joints were marked, on the upper surface,
with transverse wrinkles, which gave their lateral edges a wavy
appearance, and that the slightly prominent posterior edge of many
of these joints seemed to be faintly and irregularly puckered.
Some of the largest individuals had already cast off their hinder-
most joints ; in others, the last " scarred^^ joint was peculiarly
altered ; it was much enlarged, but had at the same time taken
quite an irregular shape, with blunt projecting angles at the sides ;
the sexual aperture at the side, and the small scar on the
posterior edge, alone betokening its true natui^e.

Sixth experiment. — A mongrel of poodle and spaniel, which
had devoured five Cysticerci on the 7th June, and twelve on the
29th J une, was killed on the 25th July, that is eight-and-forty
days after the first meal, and six-and-twenty after the second.
Out of the seventeen Cysticerci administered, fifteen were again
discovered as sexually matured tape-worms ; the smallest were
from four to nine inches long, the largest from fourteen to twenty-
six inches. In these last the posterior joints appeared already to
be longer than they were broad. In other individuals the less
elongated posterior joints had a squarish or transversely elongated
shape, and upon their exterior surface showed the above-mentioned
transverse wrinkles. The hindmost joints were cast off in
some of the larger individuals, whilst the rest still possessed
the original posterior joint, which was remarkably grown, not
being in the least degree inferior in size to the other posterior
jomts, from which, however, it was essentially distinguished by
the small scar on its posterior rounded edge.

Seventh experiment. —From the 21st May to the 5th June an
mterval of sixteen days, thirty-one thin-necked Cysticerci were
administered to a young fox. On the 13th June he was killed
and examined ; but there was not a trace in his intestines of the
Cysticerci he had eaten, either in the shape of scolices or of tape-

FEEDING WITH CYSTICEECUS CELLULOSiE.

worms, from which we may venture to conclude that the stomach
of the fox had perfectly digested the Cysticerci with which he
was fed.

I now took much pains to determine the species of these tape-
worms obtained from Cysticercus tenuicollis, and was astonished
to discover that they had all the characteristic features of
Tania serrata. The form of the eggs of the tape- worms obtained
from Cysticercus tenuicollis had first drawn my attention to the
Tania serrata, whose eggs, in form and in the number of their
investments, completely coincided with the eggs of the tape-worms
I had obtained. Comparing the head end of the latter with that
of the Tania serrata, I could neither in the outline, nor in the
suckers, nor in the hooks of the double circlet, perceive any
difference between these Tanice ; even the fully developed, as well
as the less developed joints of these tape- worms, with their trans-
verse -wrinkles, reminding one of Tania serrata.

In respect to the negative result of the seventh experiment, I
must leave the question open, whether it is not possible that the
intestine of the fox is unfit to afford a favorable nidus for the
development of the scolex of the Cysticercus tenuicollis.

3. EXPERIMENTS OF FEEDING WITH CYSTICERCUS CELLULOSE.

The Cysticercus celluloses occurs, as is well known, in such
numbers in the flesh of our domestic pigs, that from a single
muscle of one of these animals hundreds of these cystic worms
may sometimes be collected ; and even in the flesh and intestines
of man, its occurrence is not an unusual phenomenon. For the
last reason I was exceedingly anxious to try the result of feeding
with Cysticercus cellulosce, in order that I might discover from
which kind of tape-worm these Cysticerci are produced.

First experiment. — A young dog was fed, on the 22d May, with
forty-four Cysticerci ; on the 24th May, fourteen more were given
him, and on the following day, five-and-thirty. Before the Avorms
were given, they were taken out of their cysts. The dog was
killed on the 3d July, which was thirty-nine days after the last
feeding, and forty- two days after the first. Only four tape-Avorms
of two inches in length Avere found in this dog's small intestine.
From their appearance, they were evidently the product of the
Cysticerci which the dog had swallowed.

Second experiment. — Having procured two Cysticerci from a

OEIGIN OF CYSTICA AND CESTOIDEA.

67

human brain^ wliiclij when put into luke-warm water thirty-six
hours after the death of the subject, still moved, I would not, few
as they were, allow the opportunity to pass of making an experi-
ment of feeding with them ; nevertheless the young dog to whom
I administered them on the 22d May, and who Avas killed on the
14th June, that is twenty-three days after receiving them, showed
not the slightest trace of a tape-worm or scolex.

Third experiment. — On the 18th June, a young poodle
swallowed two-and-forty Cysticerci from the pig, deprived of their
cysts. The examination of this dog, on the 4th August, fifty-one
days after feeding, showed eight tape- worms of diflFerent lengths.
The smallest individual measured one inch and a quarter^ a few
others measured five and a half to seventeen and a quarter inches,
a larger individual was twenty-five and a quarter inches long,
whilst the three largest individuals had attained the length of
fifty-one inches. Notwithstanding the length which the worms
had attained, and the great number of their joints, I could
discover no perfectly developed eggs in any of the latter.

Fourth experiment. — To a young pug-dog two and thirty
Cysterci, without cysts, were administered on the 11th July, and
five-and-forty on the 17th. On the 21st July the dog was killed.
On inspecting the small intestine forty-six scolices were found, of
which the shortest measured one line, the longest six. All bore
the characteristic scar on their posterior extremities. The smallest
individuals consisted of nothing else than the head and neck of
the Cysticercus cellulosce. The remaining and somewhat longer
individuals had a transversely wrinkled body, which as yet bore
no traces of joints.

Fifth experiment. — On the 8th August, a young setter was fed
with five-and-forty Cysticerci, which were still in their cysts and
enclosed in flesh. On the 21st August, this dog was likewise
killed. In his small intestine only a few tape-worms in
course of development, of three fourths of an inch in length
were found. '

I must here remark that the dogs I made use of for the second,
fourth, and fifth experiments were troubled with the distemper a
thmg of common occurrence amongst young dogs, and that the
disease had probably had an injurious efi'ect upon the development
of the tape-worms. Notwithstanding that these experiments of
feeding the dogs with Cysticercus celluloses afforded no such com-
pletely favorable results as the foregoing series, they nevertheless

FEEDING WITH CYSTICEIICUS CELLULOSVE.

■went far enough to prove that the Cysticercus celluloses may also^ in
the intestine of the dog, become developed into a Tania.

The few Tanice which were obtained from these Cysticerci
were, moreover, a source of great perplexity to me, for when I
attempted to define the species to which they belonged, I was
doubtful whether to consider them as appertaining to the Tcenia
serrata or to the Tcenia solium. The head and perfectly developed
joints accorded with either species, only the neck was longer and
more slender than that of Tcenia serrata, so that I was inclined
to regard them as Tcenia solium. Owing to the resemblance of
these tape- worms, Tcenia serrata and solium, to one another, I
was induced to submit the specimens of Tcenia solium in my
collection to a more searching examination, and to compare them
with the examples of the Tcenia serrata taken out of the dogs.
To my no small astonishment I found individuals amongst Tcenice
which had been taken from the human subject that were not to be
distinguished from Tcenia serrata. They had the short broad
joints with transversely wrinkled integument and undulating
posterior edge, just like Tcenia serrata ; the head, too, was formed
exactly like that of the latter, though the neck was more elon-
gated. Besides these, there were a few feeble individuals
amongst them, which fully corresponded with some of the tape-
worms produced from Cysticercus pisiformis ; and the eggs of the
Tcenia solium were not distinguishable from those of the Tcenia
serrata, so that I was forced to conclude that Tcenia solium and
Tcenia serrata were identical. In order to obtain a still clearer
insight into the matter, I further compared the heads with their
apparatus of hooks of Cysticercus pisiformis, longicollis, and
cellulosce with one another, and in these also I could find no
difierence.

With regard to the length of the neck, and the circumference
and contour of the joints, though there are, as I have already
partly shown, discoverable difi"erences, they are not sufficiently
marked to rank as distinctive characters of two species of tape-
worms, and I must therefore maintain that Tania solium and
Tcenia serrata belong to one and the same species ; that they are
the extreme forms of a single species, connected by a series of
transitional forms.

OEiaiN OF CYSTICA AND CESTOIDEA. 69

4. EXPERIMENTS ON FEEDING WITH CCENURUS CEREBRALIS,

In order to make as sure as possible with these experiments, I
took clogs, which I had selected for feeding, into the country
with me, to the very place

where there were sheep affected ^^S- 29- F'g- 30.

by the staggers, and let them
swallow the cystic worms
fresh from the sheep affected
with the disease, that had just
been killed. If the parental ^
vesicle were small, and only
covered by a few clusters of

scolices, they were left in connection with it ; but if the parental
vesicle had attained a considerable size, it was divided and given
in portions to several dogs. (l^ig. 29.)

Fig. 31.

Fig. 32.

Fig. 33.

TJ

a h

Fig. 29. A portion of the parental vesicle with an attached colony of involuted scolices
of Cmnurus cerehralis from the brain of a calf, seen from the external surface, of the
natural size. Each of the separate rounded corpuscles corresponds with a scolex
developing or developed by internal budding : a, a complete involuted scolex ; b, a still
imperfect involuted scolex; c, many scolices commencing their development.

Fig. 30. A bit of the parental vesicle with a colony of everted scolices of Cmnurus
cerehralis from the brain of a calf, seen from the external surface, and of the natural size.

Fig. 31. An everted scolex detached from its parental vesicle (fig. 30), and mag-
nified to the same extent as the succeeding figures, a. The protruded double circlet of
hooks on the cephalic extremity, b. One of the four cephalic suckers, c. Fragment of
the detached parental vesicle.

Fig. 32. The head of a similar scolex seen from above ; the double circlet of hooks
surrounded by the four suckers is seen in the middle.

Fig. 33. Various hooks from the double circlet of the scolices of Cmnurus cerehralis.
a. A long hook of the inferior circlet seen from below, b. The same from the side.
c. A short hook of the lower circlet also viewed laterally, d, e. Two not yet fully
developed and soft hooks from the young buds, fig. 29 c.

70

FEEDING WITH CCENUEUS CEEEBRALIS.

First experiment. — On the 29th of May, a young dog was made
to swallow a cyst with nearly a hundred scolices. He was killed
on the 3d of June, that is, five days afterwards, and sixty-five
free and everted scolices were found in the small intestines.
Their length was from half a line to one and three quarters ;
they showed no trace of joints or transverse folds, and each
exhibited on the posterior end of the body a small kind of
cicatrix-like indentation, which plainly denoted the spot where the
scolex had separated from the parental vesicle. (Fig. 34, A, B.)

Second experiment, — On the 6th of J une, a young dog
swallowed a large Coenurus-Ye^icie, which was covered with

several clusters of scolices. When,
on the 26th July, the dog's small
intestine was examined, it afibrded
an enormous number of tape-
worms j I counted six hundred and
forty individuals in the most vari-
ous stages of development and
growth. The longest, with its
many joints, measured twenty-three
inches ; the shortest, having a length
of two lines, were still unjointed,
and yet perfectly resembled scolices.
In all, the scar on the last joint,
or on the imjointed posterior end
of the body was not to be mistaken.
(Fig. 34 and 35*.)
Third experiment. — On the 28th July a young terrier was
fed with part of a large Coenurus, and was killed on the 5th
August, after a lapse of thirty-eight days. In his intestine
there were seventy-one tape-worms variously developed. Three
of the least developed individuals were from one and a half to
two lines long, and appeared to resemble a scolex most com-
pletely, their smooth posterior end being devoid of joints;

Fig. 34. Different tajniae developed in the intestine of the dog, from the scolices of
Coenurus cerebralis. A. A scolex one inch and three quarters long, with smooth and
protruded body, viewed from the edge. B. The same scolex seen from the surface.

C. A scolex three lines long; the articulation is beginning at the lower extremity.

D. A still longer and more developed scolex, at whose hinder extremity the formation of
proglottides has taken place to a great extent. * Scar, or place by which these tmnias
were fixed as scolices to the parental vesicle.

OEiaiN OF CYSTICA AND CESTOIDEA.

71

seven others were from four to six lines long^ and showed a
commencing articulation. A few worms of six lines in length
appeared already distinctly jointed. Amongst the remaining
specimens that had become fully developed into Teenies, several
had attained the length of from sixteen to twenty- six inches.
(Fig. 35). In the longest individuals the development of the

Fig. 35.

eggs was completed, in several shorter ones the characteristic
scar on the last joint was wanting, and from the posterior edge
of the last transversely truncated joint one could plainly per-
ceive that these Tcenm had already cast oflF matured joints {pro-
glottides), and indeed it so happened that the dog had passed
tape- worm jomts with his faeces several days before his death.
Fourth experiment.— On the same day with the last mentioned

Fig. Zb. kTcBuia serraia, produced from a scolex of Cconurus cerebralis in a dog's
«r„lw?i" TX^""' ^--aermost joints are fully formed

, ^ ''''"""'^ ^^'^^ (*) clearly indicates

that no proglottis has yet detached itself from this tape-worm.

FEEDING WITH COENUEUS CEEEBRALIS.

dog, a young hound devoured a similar allowance of Coenurus.
He was killed on the 6th August, a day later than the other one.
On searching his small intestines eighty.six worms were dis-
covered, of which the majority had grown into jointed Tanice of
three to ten inches in length, whilst several individuals of from
four to five lines long only showed faint signs of the transverse
wrinkling, and a few of from one to two lines long were still in
the scolex condition without any folds.

Fifth experiment. — Another young hound was, in the same
manner, fed, on the 28th July, with the same number of Ccenuri.
There might have been about a hundred scolices attached to the
coat of the parental vesicle. On the 10th August, the dog was
killed after having passed tape-worms an ell long for several days
previous to his death. On dissecting the dog no trace of tape-
worms could be found.

Sixth experiment. — On the 1st August, a young setter swal-
lowed a piece of Coenurus with about a hundred scolices on it.
The dog was opened on the 23d August, and showed seventy-
three worms, of which only a few individuals of one to two lines
long, resembled everted scolices, whilst the remaining ones of
one to four inches long had already all the distinguishing cha-
racters of Tanice. The characteristic scar was not to be seen in
any, whether with or without joints.

Seventh experiment. — On the 1st August, at the same time
with the subjects of the foregoing experiments, a similar portion
of Coenurus was given to a mongrel- dog, (a cross between the
setter and wolf-dog). This dog subsequently suffered from the dis-
temper for a considerable time, and was killed on the 25th August.
His intestines contained many full-grown thread-worms, {^Ascaris
marginata), and a few scolices of Tcenia cucumerina, but no trace
of worms that should have resulted from the feeding with Coenurus
cerebralis. The distemper had probably occasioned the failure of
this experiment.

For the rest, the determination of the Teenice which I had
obtained from these experiments of feeding with Coenurus cerebralis
was not difficult, the characters of the Tcenia serrata being, in all
of them, clearly and sharply marked.

It must have been remarked that in the third and fourth
experiments (in which the scolices were retained in the dogs^
intestines an exactly similar period of time), the T<Bni(B in the
one dog were twenty-two inches long, whilst those in the other

OKIGIN OF CYSTICA AND CESTOIDEA.

73

dog were only ten inches. This unequal development of the
Tani(B within the same period of time is probably to be ac-
counted for by some special peculiarities of the circumstances
into which, in these cases, the scolices of the Coenurus cerebralis
had been conveyed.

There is yet another remarkable phenomenon which Avas
brought to light by the experiments on feeding with Cosnwus
cerebralis. It is that in each separate case, worms, of a very
dissimilar stage of growth were produced, although every indi-
vidual dog had been fed only once with scolices of Coenurus
cerebralis. This diversity in the growth of the scolices conveyed
at the same period of time into the same intestine, may, perhaps,
originate in the various stages of development of the scolices
at the time of their introduction. It is known that the parental
vesicles of the Coenurus go on growing without intermission,
and that fresh scolices are, by the process of budding, continually
springing forth on their inner surface. Through these peculiar
conditions of the Coenurus cerebralis, older scolices long since
perfected, and only awaiting the opportunity of further develop-
ment, were conveyed into the dogs^ stomachs, together with
younger ones, some of them only just formed, some, again, not yet
fully developed. From this point the older scolices proceeded
rapidly to their further development, and to the generation of
proglottides, whilst the younger scolices grew more slowly, and
the youngest forms, whose gemmation was not yet quite com-
pleted, were, probably, incompetent to pass from the stomach
into the small intestines of the dog, but yielded to the digestive
powers of the former.

Experiments on feeding with Echinococcus veterinorum.

The Echinococcus veterinorum, which is of such common
occurrence in the liver and lungs of our domestic cattle, does
not, probably, differ specifically from the Echinococcus hominis,
whose parent vesicle often attains such an enormous size in
the most widely different viscera of man, and by its growth
so obliterates the substance of the organs round about it, as
to bring about the death of its host. The experiments of feeding
with these worms which I made on twelve young dogs and a
young fox, I have already fully described.^ For each experiment

' See the ' Zeitschrift fur Wiss. Zoologie,' Bd. iv, 1853, p. 409, Taf. xvi, a, fig. 1—9.

74 FEEDING WITH ECHINOCOCCUS VETEEINOEUM.

the contents of a fruitful Echinococcus-yesicle were employed.
That is to say, free scolices developed by gemmation were taken
out of the Echinococcus-\esic\e, mixed with luke-warm milk,
and poured down the dogs^ throats; the latter, after having
in this manner been made to swallow a considerable quantity
of the young of the EcMnococcus, had some pure luke-warm milk
given to them, which they licked up with avidity, so that
these continued acts of deglutition made sure of the small Echi-
nococcus-lsirv2e or scolices being washed into the dogs' stomachs.

The examination of these dogs after death proved, that the
scolices of the EcMnococcus veterinorum, when conveyed into
the dog's digestive canal, do not perish, but, under certain
favorable circumstances, develop into proper sexually matured
tape- worms, possessing only a couple of joints. After the
feeding, they passed without obstruction from the stomach into
the small intestine of the dogs, where, in proportion to the
number of scolices administered, they were found in immense
numbers fully extruded from their receptacle, whilst, when in
the interior of the parent vesicle, they are almost always to be
found retracted within it. After remaining from fifteen to
twenty days in the dogs' intestinal canal, these scolices, which
when administered were without joints, exhibited a two-jointed
body. After twenty-two days, the body was divided into three
joints, and from this time forward these little tape- worms ceased
to increase in length, or to become further divided, whilst
the sexual organs began to appear in the two posterior of the
three articulations. The development of the eggs in the sexual
organs of these little worms was to be seen twenty-six days
after the feeding, and the embryo appeared on the twenty- seventh
day.

With the maturity of their sexual organs, and the division
of their body into three joints (and hence with the pro-
duction of only two Proglottides), I concluded these worms
had attained their perfect state) from the circumstance that
amongst the three-jointed little tape- worms in the dogs' small
intestine, I discovered several individuals which had already,
twenty-seven days after the feeding, thrown off the circlet of
hooks. The loss of this apparatus amongst Tanice furnished
with it, is a proof of mature age. When I endeavoured to
determine the systematic position of the tape-worms which
had been developed from the scolices of the Echinococcus vete-

OEIGIN OF CYSTICA AND CESTOIDEA.

75

rinorum and which did not exceed one^ or one and a half lines in
lengtli, there was not a single species of Tcenia among the many-
admitted by helminthologists, with which they agreed. I was
soon convinced that this small species of tape-worm had been
hitherto overlooked by helrainthologists ; for it cannot but be
admitted that this transformation of the young of the Echino-
coccus into sexually-matured Tcenice may take place independently
of artificial feeding. In our slaughter-houses, similar scolices
must certainly often find an opportunity of entering into the
intestinal canal of dogs, the Ec/iinococcus-vesicle, cut out of
the viscera of the slaughtered animals and thrown away, being
no doubt frequently devoured by the former. It was such a
brood of Tceni(B developed from the yoiing of the Echinococcus that
Rudolphi probably saw, when he believed that he had discovered
in the intestine of a dog, young tape-worms, which were assumed
to have been developed by equivocal generation from the villi of
the mucous membrane.^ The little three-jointed tape-worms
which Roll twice found in dogs, and which were not long ago
described by him as young individuals of Tcenia serrata, must
also of a certainty have owed their origin to scolices of the
Echinococcus veterinorum?

The specific form of the hooks of the circlet of the scolices of
the Echinococcus veterinorum, as well as the very small number
of Proglottides generated by them, justify me in considering the
T(Bni(B developed from these scolices as a distinct species, which I
have denominated Tcenia echinococcus. (See the ' Zeitschrift
fur Wiss. Zool.,^ B. IV, 1853, p. 423).

If we sum up the results of these experiments on feeding
with Echinococcus veterinorum, they may be shortly stated as
follows :

1. Sexually-developed Tcenice have been produced out of all
those kinds of scolices known as cystic worms which have been
employed for feeding experiments.

2. From the scolices of the Cijsticercus pisiformis, tenuicollis,
cellulose, and Ccenurus cerebralis, Teenies of an eU long have
been produced, which perfectly agree with both the Tcenia
serrata, and with the Tcenia solium,

J^S,e his'Entozoorum sive vermium intestinalium historia naturalis,' vol. i, 1808,

Jr ?f M^" -''^ T Entwickelungsgeschichte der Ta^nien,' in theVerhandlungen
der Physikal. Medizinischen Gesellschaft in Wurzburg,' Bd. iii, 1852, p. 55.

76

SPECIES OF CYSTICA AND CESTOIDEA.

3. The scolices of the Echinococcus veterinorum developed
themselves into very small tape-worms, of from one, to one and a
half, Imes long, which have been shown to be a distinct species,
and named Taenia echinococcus.

It may seem questionable to many helminthologists and
zoologists, that four different kinds of cystic worms, which have
hitherto been looked upon as so many distinct species, should
only produce one and the same species of Tcenice. But I
would ask, are the cystic worms which have been termed Cysti-
cercus pisiformis, tenuicollis, celluloses, and Ccenurus cerebralis,
really distinct kinds ? After the present inquiries, this question
must be negatived. All these cystic worms are only the
degenerated embryos and scolices of a single species of Toinia.
If they who have always regarded these cystic worms as belong-
ing to different species will make the experiment for themselves
of detaching the several heads of the four above-named cysticerci,
and mixing them together, they will find it utterly impossible to
make out any specific difference between them. Further than
this, I not only question if the Tcenia serrata from the intes-
tine of the dog, and the Taenia solium from the human intes-
tine are distinct and sharply defined species, (see p. 68), but I
also doubt the specific distinctness of the Tania marginata from
the intestine of the wolf, of the Tcenia crassicejjs from that of the
fox, and of the Tcenia intermedia from the intestine of martens
and polecats. All these five Taeniae certainly belong to but a
single species of tape- worm, and only present varieties of race
dependent on the influence of the varying circumstances to which
the young Taeniae are exposed in the course of their further deve-
lopment, according as they have entered the digestive canal of a
man, a dog, a wolf, or any musteline carnivore. If we consider
the diagnoses of these five kinds of Taenics given by helmintho-
logists, we shall be convinced that there is not a single specific
mark of distinction to be found between them, and that the form
and arrangement of the circlet of hooks of these tapeworms are
entirely disregarded. If the heads of the five above-mentioned,
so-called species of tapeworm, with their circlet of hooks Avere
submitted to the inspection of the most experienced helmintho-
logist, without betraying their origin to him, I feel persuaded that
he would be perplexed in distinguishing those five species of Taeniae,
which only differ according to their various habitations. In the
genera Ligula, Schistocephalus, Tetrarhynchus, and Echinorhynchus,

DISEASES PEODUCED BY CYSTICA.

77

helmintliologists have long ago observed that certain species
inhabit and attain sexual maturity in the most different kinds of
birds and fishes. The conditions of life of the five races of
degenerated Tcenice serratoi (with their various oedematous forms of
scolex, which are also to be considered as varieties of race), were
certainly originally more simply and sharply defined, and must
have gradually become impressed with their present complex and
indefinite character from the domestication of the animals they
infest.

At the same time, the resiJts of these feeding experiments,
which I have just cited, contradict the belief that the cysts of
these worms have a physiological,^ and not a pathological signifi-
cation, for all the Cystica mentioned are produced from a single
species of tape-worm, namely, the Tatnia serrata, and it only
depends upon the nature of the spot to which these embryos
have been transplanted after having completed their immigration,
whether they degenerate into Coenurus cerebralis, or Cysiicercus
pisifonnis, or tenuicollis, &c. When subject to the same external
influences, these degenerations will always present the same form ;
whence it seems justifiable to compare these continually recurring
and sharply-marked modes of degeneration of certain intestinal
worms with the phenomena of race.

5. ON THE DISEASES PRODUCED BY CYSTIC WORMS, AND THEIR

PREVENTION.

After having pointed out, in the introduction, that all the
intestinal worms reach the interior of their hosts by immigration,
and after having shown by the feeding-experiments, that certain
cystic worms are transformed in the digestive canal of dogs into
a particular kind of tape-worm, I may be allowed to draw the
conclusion that, reversing the circumstances, the young of these
tape-worms may, by the help of the alternation of generations
which I have already described, be developed into cystic worms,
the species of the animals and also the nature of the organs into
which the immigration takes place, exercising a specific influence

' Kiichenmeister has taken much pains of late to defend this view, in opposition to
rnme, and has been led away by his zeal, to depart from that calmness of tone which
becomes scientific controversy.

78

THE STAGGERS.

on the development and form of the cystic worms, and giving
rise to many kinds of distinct degenerations (races).

By keeping in view these highly interesting vital conditions of
certain intestinal parasites, we shall be enabled to take more
efficient means against the spread of cestoid and cystic worms, in
those cases in which their presence is prejudicial to the animals
they inhabit, than could be the case so long as no one was
aware in what way these parasites, Avhose entrance it was so
desirable to prevent, made their way into the creatures they
infested.

What purposeless and useless remedies have been proposed for
this same worm-disease, we gather, amongst other things, from
the numerous treatises which the disease of the " staggers'^ in sheep
has called forth. On account of not ha^^.ng a correct acquaint-
ance with the natural history of the Cystica, there necessarily
arose the most contradictory and unreasonable opinions, and
upon these a series of prophylactic and curative measures have
been founded, which, resulting in no success, have been one after
another discarded again. Amidst such irrational proceedings, we
cannot blame the sheep owners if they entirely gave up using
means for the eradication or prevention of the staggers, and
unwillingly submitted to a loss that, amongst rich flocks, was
by no means to be lightly estimated, amounting in many sheep-
farms to more than ten per cent.

Were I to bring forward all the various causes to which the
origin of the Ccenurus has been referred, I should far exceed the
limits that I have assigned myself in these pages. That the
doctrine of equivocal generation played a conspicuous part therein
will surprise no one, since there yet exist veterinary surgeons
who adhere to that doctrine in all points.

The only mode of insuring the destruction and removal of the
worm, and hence the only effectual cure for the disease of the
staggers, is trepanning. Unfortunately this process is not appli-
cable in all cases — since it depends upon the situation of the
worm, whether it can or cannot be reached by trepanning. The
operation is of course admissible only when the Ccenurus cere-
bralis is imbedded in the anterior and upper portion of the
ruminant's brain, whilst if, on the other hand, it be deeply
seated in the base of the brain, or in the spinal marrow, it cannot
be reached by trepanning. For this reason the testimonies as to

DISEASES PEODUCED BY CYSTICA.

79

the result of this operation vary so widely. Operators who have
accidentally fallen in with cases where the Ccenuri were super-
ficially situated, have been successful, and so have gained credit,
whilst other cases have completely baffled them. Not only the
deep-seated position of the Coenurus cerebralis occasions the
ill success of the operation, but even postponing it so long
that their size is already so great as to have produced much dis-
turbance in the efficiency of the brain, may render the removal
of the worms useless. Further, trepanning may also have come
into discredit as an inefficient means of cure for the staggers,
from having been applied on the appearance of dizziness which
had been produced by other causes than the existence of a
Coenurus cerebralis.

Here I cannot refrain from remarking, that in the south of
Germany, namely, in the Suabian part of the kingdom of
Bavaria, the Cmnurus cerebralis not unfrequently appears in
oxen; whilst in the north of Germany this disease is scarcely
known in cattle. The common occurrence of the staggers
amongst these domestic animals is probably the reason why
trepanning has been recently tried as a cure for calves affected
with the staggers. I have to thank Dr. Gierer, the provincial
veterinary surgeon at Tiirkheim, who has performed the ope-
ration with success on several oxen, for his very interesting
communications on this subject, amongst which the following
points appear particularly worthy of notice.

M. Gierer is persuaded that the disease of the staggers amongst
oxen is by no means of very unfrequent occurrence, but as
hitherto no certain means of cure has been found for this evil,
all the calves affected with the disease have been sold betimes to
the butchers. Even M. Gierer, before he succeeded in curing by
the trepan, had heard remarkably little in his own circle of the
appearance of this disease amongst oxen; now, however, after
having thoroughly cured eight and twenty oxen out of thirty
which he trepanned, he is able to form some idea of the frequency
of the complaint amongst the animals, being consulted oftener
than ever about the cure of this disease.

I have compared several examples of Canurus cerebralis which
Gierer obtamed by trepanning from young oxen, mostly of from
about two to three years old, with the Ccenurus cerebralis of
sheep, and have found no specific difference between the two • so
that I conclude that the Coenurus of the ox also originates in the

80

TREPANNINa FOR CCENURUS.

TcBma serrata. Beyond this, the cysts of these Coenuri ;vere of
extraordinary dimensions, since they would have exceeded the
size of hens^ eggs if, when in a fresh condition, they had been
filled with water. They, moreover, contained a remarkable
number of scolex gemmae, which covered the interior surface of
the cyst in masses thickly pressed together. Very many of the
already developed scolices were everted, so as to project con-
siderably on the exterior surface of the parent cyst, a pheno-
menon which I have seldom observed in those of sheep.

Although the fact has been proved, that the disease of the
staggers, arising from the presence of Coenurus cerebralis, can
be cured by trepanning, still sheep-owners must not always
reckon upon the absolute success of the operation, since, as has
been already stated, the result must depend upon the situation
of the parasite ; and as it is impossible to know if two, or even
several cysts, may not have established themselves at the same
time in the nervous centres of the affected animal, of which one
alone could be removed by trepanning, and that the cyst which
lay nearest to the surface. Furthermore, even though the
animals can be cured by the removal of these parasites, the
question arises, if such animals, the vital powers of whose brain
have been disturbed by the presence of this cyst, can be said to
be cured in the full meaning of the word ? Do the diseased
changes which a considerable- sized Coenurus-cjst engenders,
through displacement, pressure, and wasting away of the sub-
stance of the brain, become so entirely removed after the extrac-
tion of the worm, that the vital powers of the brain can be again
restored in their full integrity ? Will there not still remain
traces of changes engendered by the disease in such a brain,
which although causing no striking interruption of the animaFs
nervous energies, may yet more or less affect its strength, dura-
tion of life, and fruitfulness, and render it inferior to a thoroughly
healthy individual of the same race.

From what has been stated, it follows that the cui'c of the
staggers, when it has once broken out, is always a difficult, and
very often an impossible task; hence it would be much more
worth while to take precautions for preventing it. The only
rational prophylactic treatment must consist in employing such
means as may prevent the immigration of the young of that tape-
worm from which the Ccenuri are developed. As, according to my
experiments, the Cmnurus cerebralis changes, in the digestive canal

DISEASES PEODUCED BY CYSTFCA.

81

of dogs, into the Tania serrata, I venture to assume that the
young of this tape-worm, after its immigration into ruminants,
becomes developed in their nervous centres into the Coenurus
cerebralis, which, according to the situation it occupies, produces
either vertigo by pressure upon the brain, or the phenomena
characteristic of pressure upon the spinal marrow.

The only prophylactic measure against the morbid conditions
induced by the Coenurus cerebralis must therefore be — to guard
against the immigration of the young of the Tania serrata.

It will possibly be objected that, even if the generation of
the Toenia serrata out of the scolices of the Coetiurus cerebralis
had been proved, the production of the Coenurus cerebralis from
the young of the Tcsnia serrata must first be demonstrated,
in order that, from the facts before us, we may have the right
to consider immigrated young Tcenia as the cause of the
staggers proceeding from Coenurus cerebralis. The laws of pro-
pagation of these animals long since suggested the view I have
just put forth, but recently I have been put in possession of facts
■which directly support it. Dr. Haubner, professor at the vete-
rinary school in Dresden, has in fact had the goodness to com-
municate to me that in that establishment, on the 7th of J anuary
of this year, several lambs were fed -with perfect joints of the
tape-worm of dogs, containing ova, and that on the 20th of
January the first appearances of the staggers manifested them-
selves at the same time in all, whilst the remaining animals of
the flock to which those lambs belonged continued healthy. The
diseased lambs were killed and examined in succession at intervals
of eight days, by which proceeding Professor Haubner obtained
the following results :^

"At the commencement of the disease various symptoms
of irritation and inflammation of the brain appeared, which
perfectly accorded with those which Dr. Haubner had already
become fully acquainted with in cases of the so-called spontaneous
development of this disease. In this stage the sheep might
either die, or else the irritation of the brain might pass away,
and the Coenurus-cysts proceed to further development. Upon
dissection after three or four days, reckoning from the first
appearance of the disease, Dr. Haubner found many cysts in the

1 A short communication upon this subject has just been made by Professor Haubner
to ' Hamms Agronomische Zeitung,' 1856, No. 10, p. 157.

6

83

PEOPHYLACTIO MEASURES.

brain, about the size of a pin's head. They lay partly free on
the vessels in the convolutions of the brain, partly imbedded in
superficial canals formed of exuded matter, the substance of the
brain representing the bottom, and the exuded matter the cover-
ing of the canals. The whole animal (heart, lungs, muscles,
was at the same time permeated by the encysted young of
the tape- worm. Later dissections showed fewer but larger cysts
in the brain. Mr. Haubner conjectures, and rightly so, that
the rest were abortive and died away. After fourteen days,
always reckoning from the first morbid symptoms, the same
observer discovered several dark spots in a few of the cysts,
which were probably the projected heads. After four weeks all
the cysts had separate heads with distinct suckers ; and, as it
appeared, with the circlet of hooks in course of development."

After having thus proved by facts that the immigrated young
of the Taenia serrata in ruminants can develope into Cosnurus
cerebralis} I feel justified in advising, as the most important
preservative against the Coenurus, that the immigration of the
young of the Tcenia serrata into ruminants should be prevented.
The utility of this advice will certainly be admitted by every one
who has made himself acquainted with the history of the intestinal
worms in the foregoing pages of this pamphlet ; but beyond
this, persons will be also desirous of knowing how it can be
practically carried out. When I consider the many hidden paths
by which most of the intestinal worms make their way during
their existence, I must confess once more that it will be a most
difficult task for those engaged in the breeding of cattle to
prevent the excessively small young of the tape-worm from pass-
ing into their oxen and sheep.

It may be safely assumed that the young of the tape-worm
pass with the food into the digestive passages of the ruminants
whilst they are eating and drinking. How easily the fi-esh as
well as the dry fodder of ruminants may become contaminated
with the ordure of dogs containing eggs of the Tania serrata ;
especially when we remember that these eggs possess great
tenacity of life, and are able to withstand for a considerable time
external injurious influences, such as cold, heat, drought, &c.

> Through the kind communication, by letter, of Professor Leuckart, of Giessen, I
have just heard that he has succeeded in generating the Cysticercus fasciolaris in tlie
livers of white mice, after having given them sexually developed joints of the tape-worm
of the cat ( Toenia crassicollis) to eat.

DISEASES PEODUCED BY CYSTICA. 83

If we fix our attention upon sheep^ -wliieh are unfortunately
too often exposed to the dangerous attacks of the Cmnurus
cerebralis, we shall find that very frequently when a flock of
sheep is attacked by the Ccenurus cerebralis, it is the sheep-dog
who has guarded them year after year who is answerable for
the mischief; in this case the shepherd's dog is infested by the
Tarda serrata, whose youngs after being passed by the dog in the
neighbourhood of the flock, are easily caught up and swallowed
by one sheep or another without being observed. The surest
meanSj then, of keeping ofl" the Ccenurus cerebralis from a flock
of sheep would be to do away with the sheep-dog. To this,
however, the sheep-breeders would hardly agree, since the ser-
vices of a first-rate sheep-dog are not to be easily replaced by
any other kind of help. But that the sheep-dog is really con-
cerned in the devastations which the Ccenurus cerebralis makes
in a flock is borne out by the fact that those sheep-flocks which,
in the true sense of the word, are stall-fed, and consequently
unattended by a dog, are never,, or at least very rarely, troubled
with the Ccenurus cerebralis. Those sheep-breeders who are
disinclined to give up keeping dogs to guard their flocks, could
urge as an objection that their dismissal would afibrd no sure
guarantee for keeping off the parasite, inasmuch as the pastures
where the sheep feed might become contaminated by the young
of the Tania serrata through other dogs, such as hounds and
mastiff's j perhaps, indeed, even by wolves, foxes, or martens, and
other animals of prey (see page 76).

Since, also, I have pointed out the identity of the Tcenia
solium of the human subject with the Tania serrata of the dog
(see page 68), there appear to be so many possible ways open
for the dispersion of the cestoid embryos and their development
into the Ccenurus cerebralis, that it needs the utmost care to
discover means of always cutting off the approaches by which
these dangerous parasites effect an immigration into the sheep.

If, after these objections, which I have myself raised, I am
the less inclined to think that the doing away with the sheep-dog
would be an absolute preventive against the Ccenurus cerebralis,
yet, I at least believe that, as a rule, and as a wise pre-
caution. It might be recommended to those sheep-owners
who employ dogs in the care of their flocks, to exercise a
watch over them. If the dog be troubled with the Tccnia
serrata, the worm should be expelled before the animal comes iu

84

PEOPHYLACTIC MEASURES.

contact eitlier Avith tlie flock or their food. This supervision of
the dog will be continually necessary, since although, according
to my experience, the period of the parasite's existence is confined
to only a few weeks, the opportunity for its immigration into the
dog may frequently occur again. For the rest, I have pleasure
in thinking that I have pointed out the true cause of the origin
of the Coenurus cerebralis, and hinted to the sheep-breeders in
what way the worm creeps into their flocks ; and I now leave it
to intelligent proprietors to employ those means which are best
fitted for the purpose of arresting the enemy, according to the
locality, the style of farming, or to the condition of the animals.
Having furnished a statement of the natural history of the
Ccenurus cerebi^alis, I must leave it to experience to show if there
are really means of preserving a flock of sheep from this cestoid
parasite, and if so, what kind of means.

The Tcenia serrata of the dog, whose presence in the sheep-dog
is most particularly to be guarded against, is easily distinguish-
able from the other, harmless, tape-worm of the same animal.

rig. 3G.

the T(Bma cucumerina ; the first having its developed joints always
white, and of a quadrangular or oblong shape, with only a single
irregular marginal sexual aperture, varying in its position on each,
whilst the developed joints of the TcBnia cucumeriria are elliptical

Pig. 3G. Tainia cncimerina, from the intestines of a dog, \vith perfectly developed
joints, natural size.

CYSTICERCI IN SAUSAGES.

85

in form, are commonly of a pale-red colour, and have on every
joint two marginal apertures opposite to each other.

The evidence that I have given in the foregoing chapter of
certain cestoids becoming changed in the digestive canal of dogs
into sexually developed tape-worms, suggests the idea that, most
probably, the greater number of the human tape-worms enter as
scolices into the intestine of man. That the opportunity for
such an immigration may readily occur is plain, if we reflect how
easily a Cysticercus may get upon the lips of a butcher or a cook
in handling pork containing these parasites. In fact, it appears
from the medical reports that persons engaged in slaughter-houses
and kitchens very commonly suffer from tape-worms,-^ Avhich
indicates that, although the use of " measly" meat for the most
part never produces dangerous results, yet that especial care
should be taken regarding it. In any case, encysted pork, when
boiled or roasted, can afford no opportunity for the production of
a Tcenia solium in the human digestive canal, since the Cysticerci
will be completely destroyed by the degree of heat necessary
for the preparation of the meat; but it is quite a different
case with smoked sausages, in the manufacture of which
many butchers make use of measly meat.^ With the present
clever and expeditious method of smoking them, how easily
may a sausage stuffed with this meat be eaten so soon and in
such a fresh condition, that one or another scolex may have pre-
served its vitality, and awakening from its trance in the human
digestive canal, proceed to its development as a tape-worm.
From what I have stated in the earlier chapters with regard to
-the internal relation of the scolices to the tape-worms, it is now
explained how that in no country are men more tormented by
these parasites than in Abyssinia, it being well known that the
Abyssinians eat a great deal of raw meat. Dr. Bilharz, formerly
a pupil of mine, some time ago wrote to me from Cairo, that in
Abyssinia the tape-worm was so common that a native would
regard it as an abnormal condition if he were to expel no tape-
worm joints J and that no slave was purchased there without at the

1 Compare Wawruch, ' Praktische Monographie der Bandwurmkrankheit,' Vienna,
1844, p. 197.

2 The shrunk Cysticerci in such sausages are very easily to be found ; they form
milk-white bodies of the size of a needle's head, which, when pressed between glass
plates and seen through the microscope, show the circlet of hooks and the four suckers
of the scolex very distinctly.

86

PROPHYLACTIC MEASUEES.

same time receiving a packet of cusso to remove his tape-worm.
That the flesh of our cattle affords the principal opportunity for
the immigration of the Tcenia solium into man, is borne out by
the experience of Eeinlein/ a physician of Vienna ; who for ten
successive years professionally attended the Carthusian monks,
who never partake of either meat or milk, but live mostly on
fish ; he had never seen a single person who had sufi'ered from
tape- worms, and was assured by the oldest fathers that they never
remembered any of their associates to have been troubled with
them.

But it is not alone in the torrid and temperate zones of om'
globe that man is visited by these parasites, for even in the polar
regions the cestoids find means of reaching him. Dr. Schleisner,
who a few years ago published a medical topography of the island
of Iceland,^ makes mention of an epidemic liver complaint or
hydatid disease which made great ravages among the Ice-
landers. In the short account of this complaint, which is
more commonly met with in the interior of the country than on
the coast, I recognise a tape- worm which is imbedded not only in
the livers, but also in the abdominal organs and in the skin of
these islanders. Professor Eschricht, of Copenhagen, wrote to me
lately that the sixth part of the whole population of Iceland
suffered from this disorder of the liver, and that with many of
them, after dreadful and protracted sufferings, it terminates in
death. From a more particular description and illustration of
this disease produced by the tape-worm, for which I am indebted
to the kindness of Eschricht, I conclude that the parasite is one of
the Cijsticerci, and has its origin in the Tcenia serrata {solium). In
Copenhagen, people's attention has already been drawn to this
cestoid disease, so highly fatal to the Icelandic population, and
they appear to be desirous of taking energetic measures for its
prevention. I entertain the belief that, bearing in mind the
natural history of the Cijsticerci as I have represented it in these
pages, it may be possible to prevent the immigration of the
cestoid young — to which, from the Icelanders' mode of life, they

1 See his ' Bemerkungen liber den Ursprung, die Entwickelung, die Ursachen, Synip-
tome und Heilart des breiten Bandwuimes in den Gedannen des Mensclien,' Vienna,
1812, p. 25.

2 See his ' Forsbg til en Nosographie of Island,' Kjobenhavn, 1849 A short abstract
of this work will be found in ' Janus/ the ' Central-Magazin fiir Geschichte und Literiir-
Geschichte der Medizin,' vol. i, 1851, p. 300.

I

CESTOID EPIDEMIC OF ICELAND.

87

are so fatally exposed — into the inhabitants of this island. How
this may be effected the following remarks may serve to show. It
is well known that the Icelanders carry on an extensive breeding
of cattle and sheep, in. which the canine race are in many ways
serviceable.^ I presume that the Icelanders, when slaughtering
their cattle, never have the dogs far off, and thereby it readily
happens that these voracious animals, in s'wallowing what is
thrown aside, take in various Cysiicerci ; from these the Tcenia
serrata is developed, and their young, by means of the oxen, give
rise to many evil consequences to man. If the dogs of the Ice-
landers were kept under supervision and free from the Tania serrata,
not only would the propagation of the young of this tape-worm
be certainly prevented, but also their immigration into man and
cattle, and their injm'ious degeneration into Cysiicerci.

It can now be no longer regarded as wonderful, or considered
as fabulous, when physicians inform us that after raw meat had
been prescribed for certain of their patients, they had found
them to become troubled with tape-worms.^ In the cases that were
met with, it was explicitly said to be the Tcenia solimn that was
expelled, which exactly supports the opinion that this tape-worm,
so rare in St. Petersburg, has there been developed by the
adoption of a diet of raw meat. The statements would have
been much more to be suspected if, in the tape- worms that were
passed, the Bothriocephalus latus, so general in Russia and Poland,
had been recognised, since this worm is never met with amongst
our cattle in a scolex condition. Formerly, the geographical
distribution of both these human tape-worms, the Bothriocephalus

1 What important services the numerous dogs spread all over Iceland render to the
inhabitants in their husbandry, is given in the more or less detailed accounts of travellers.
Compare Hornebow, ' Zuverliissige Nachrichten von Island,' Copenhagen, 1753, pp. 143
and 164; further, Hooker, 'Journal of a Tour in Iceland in the Summer of 1809,'
London, 1813, vol. i, p. 339.

Compare, upon this subject, the communications made by Weisse (in the ' Journal
fur Kinderkrankheiten,' vol. xvi, 1851, p. 384), which, in spite of Braun's objections
(ibid., vol. xvni, 1852, p. 78; or in Froriep's ' Tagesberichten,' 1852; ' Geburtshiilfe
und Kmderkrankheiten,' p. 281), are worthy of all belief. The opinion expressed by
Andral m favour of the doctrine of equivocal generation (' Grundriss der pathoI.
Anatomic, Leipzig, vol. i, p. 393), that from external mechanical influences (a contusion)
affectmg an organ, its necessary nourishment may be disturbed, so that the organic par-
icles are not fully assimilated, and become metamorphosed into lower kinds of animals
into a Cy,^,c.rc«,)-an opinion in which Professor Uhde, of Brunswick, also coincides
(see Deutsche Khnik.,' 1851, No. 40, p. 434)-is thus thoroughly refuted.

88

CONCLUSION.

latus and the Tania solium, was declared to be very sharply
defined ; the appearance of the former being supposed to be con-
fined to Switzerland, Poland, and Russia ; but now, if the Tcsnia
solium were to show itself in these countries, it would not be a
matter of astonishment nor appear unworthy of belief, since,
through the importation of cattle infested with Cysticerci, from
countries where only the Tcenia solium is found, this tape-worm
may easily be introduced in its scolex form.^

After this statement of the history of the tape- worms, and of
the Cysticerci which stand in such close relationship with them,
I trust that I may have so strongly shaken the many false views
and prejudices so deeply rooted amongst physicians, veterinarians,
and economists, with regard to the origin, development, and pro-
pagation of these intestinal worms, that they may henceforth be
renounced as untenable. I have thereby not only the satisfaction
of having uprooted the very foundations of a chateau en Espagne,
filled with the most marvellous hypotheses, but of having erected
in its place a structure compacted of facts and based upon experi-
mental demonstrations, which throw a light upon a path hitherto
wrapped in profound obscurity, but which may now be profitably
followed.

• According to a written communication, for which I am indebted to Dr. Baumert,
during liis stay in Neuchatel, the Cysticerci are almost unknown in pigs in the western
parts of Switzerland, viz., in Neuenburg, whilst all those pigs that are introduced there
from France are abundantly infested with them.

INDEX OF TAPE AND CYSTIC WORMS.

Abyssinia, 85
Acanthorhynchus, 48, 52
Acanthobothrium, 43
Agamazooids, 13
Alternation of generations, 11
Anthobothrium, 43
Anthocephalus, 48
Arion empiricorum, 39
Ascaris acuta, 26

angulata, 26

capsularis, 26

incisa, 26

marginata, 61, 72

osculata, 26

spiculigera, 26

Bats, 39

Baumert, Dr., 88
Bilharz, 85
Bojanus, 11

Bothriocephalus latus, 87
solidus, 31

Calliobothrium, 43
Caterpillar, thread- worm of, 6
Cats, 57

Caudal appendages, 52
Cercaria armata, 21

encysted, 22

ephemera, 16

sacs, 15
Cercariae, 15

Cestoid Entozoa, origin of, 57
Ccenurus, 48

cerebrahs, 29, 80

cerebralis, experiments on feed!
with, 69

cerebralis, origin of, 84
Creplin, Dr., 32
Cysticercus, 48

cellulosae, experiments of feedi

with, 66
fasciolaris, 54

Cysticercus of rats and mice, 57

pisiformis, 59

tenuicollis, 53, 62
Cystic Entozoa, origin of, 57
Cysticerci, experiments of feeding with, 64
Cystic worm, diseases produced by, 77

Diesing, 48
Distomata, 5, 7.
Distomum echinatum, 19

hepaticum, 7

militare, 19

trigonocephalum, 19

uncinatum, 19
Dog, 37

Echeneibothrium, 43
Echinococcus, 48

Hominis, 29

Veterinorum, 73
Egg-shell of intestinal worms, 6

solidity of, 6
Entozoa cephalocotylea, 48

cystic, 47
Ephemeridae, 20
Eschricht, 86

Feeding with Cysticercils, 59
Filaria cystica, 26

Insectorum, 8

Piscium, 26
Fluke, 7

Gastropacha Neustria, 10
Generations, alternations of, 14
Gierer, Dr., 79
Gordius, 8

aquaticus, 11
Gyrodactylus, 44

Hsematozoa, 29
Haubner, Dr., 81
Hydra tuba, 44

18

274

INDEX OF TAPE

AND CYSTIC WOEMS.

Iceland, 86

Intestinal worms, origin of, 3

King's yellow snails, 11

Leuckart, Professor, 82
Libellulida:, 20
Ligula, 45

alternans, 32

simplicissima, 32

sparsa, 32

uniserialis, 32
Liparis chrysorrhoea, 10
Livers of Sal mo, 33
Lumbricus hydropicus, 53
Lymnaeus stagnalis, 21

Measly meat, 85
Meissner, 39
Merniis, 8

albicans, 10

embryos of, 10
Monostomum mutabile, 17

Nurse, Steenstrup's title of, 13

Oken, 11

Onchobothrium, 43

Parasites, strayed, 27
Perch, 33
Perlidse, 20
Phryganidae, 20
Phyllobotbrium, 43
Piestocystis, 48
crispa, 52
Pike, 33

Pontia Crataegi, 10
Pterobothrium, 48, 52

Rabbits, 59

Races, 50

Rats, 57

Raw meat, 87

Receptaculum Scolicis, 51

Redstart, 39

Reinlein, 86

Remedies for worms, 78
Rhynchobothrinm, 34, 45
Roll, 75

Round worms, 4

Rudolpbi, 34, 48

Salmo salvelinus, 33
Schleisner, Dr., 86
Scolex, 48

Schistocephalus dimorphus, 32
Sertularidae, 44

Siieep, Coenurus cerebralis in, 83
Solitary worm, 5
Staggers, 79
Steenstrup, 12
Stein, 52

Stein of Tharand, 38
Stenobothrium, 48
Sticklebacks, 31
Strongyli, 7
Strongylus filaria, 7

Taenia crateriforrais, 36
cellulosae, 53
crassicollis, 54
cucumerina, 84
fimbriata, 42
hydatigena, 52
longicoUis, 34, 54
ocellata, 34
of cats, 57
serrata, 61, 71

serrata, emigration -of the young of, 81
solium and Taenia serrata, identity of,

83

vesicularis, 52
Tape-worm, 4, 31
Tenebrio molitor, 38, 39
Tetrabothriorhynchus, 48
Tetrarhyncbus,'34, 43, 45
Thread-worms of caterpillars, experiments
on, 9

Thysanosoma actinoides, 42
Trematoda, 14

Triaenophoi us nodulosus, 29, 32, 33, 54
Trichina spii'alis, 25

Van Beneden, 47
Vermes cucurbitini, 41

White mice, livers of, 82

Yponomeuta, 10
evonymella, 9

LIST OF THE WORKS PUBLISHED BY THE
SYDENHAM SOCIETY FROM ITS
FOUNDATION IN 1843,

IN THE ORDER IN WHICH THEY WERE ISSUED.

FOR THE FIRST YEAR, 1843-4.

* " Hecker's Epidemics of the Middle Ages." 1 vol., 8vo, pp. xx, 380.

* "Louis on Phthisis." 1 vol., 8vo, pp. xxxv, 571.

" Th. Sydenham Opera Omnia." I vol., 8vo, pp. xxx, 668.

FOR THE SECOND YEAR, 1844-5.

* "The Seven Books of Paulus JEgineta." Vol. I, pp. xxviii, 683.

* " Observations on Aneurism." 1 vol., 8vo, pp. xii, 524.

* Simon's Animal Chemistry." Vol. I, 8vo, pp. xx, 360, plate.

FOR THE THIRD YEAR, 1845-6.

* " Simon's Animal Chemistry." Vol. II, 8vo, pp. xii, 560, 2 platee.

* " Paulus JEgineta." Vol. II, 8vo, pp. xi, 511.
' Hasse's Pathology." 8vo, pp. xvi, 400.

FOR THE FOURTH YEAR, 1846-7.
' The Works of W. Hewson." 1 vol., 8vo, pp. Ivi, 360, portrait and 8
plates.

' Dupuytren's Lectures on Diseases and Injuries of Bones." 1 vol., 8vo,
pp. xvi, 459.

'The Works of W. Harvey, M.D." Complete in 1 vol., 8vo, pp. xcvi,
624.

FOR THE FIFTH YEAR, 1847-8.

* "Paulus JEgineta." Vol. Ill, pp. viii, 653.

' Feuchtersleben's Medical Psychology ." Pp. xx, 392.
'Microscopical Researches of Schwann and Schleiden." Pp. xx, 268,
6 plates.

* Memoirs of the French Academy of Surgery." Pp. x, 293.

FOR THE SIXTH YEAR, 1848-9.
' Rhases on the Smallpox and Measles." 8vo, pp. viii, 212.
The Genuine Works of Hippocrates, translated from the Greek"
Vol. I, 8vo, pp. X, 466.

The Works of Sydenham, translated from the Latin." Vol I 8vo
pp. cvi, 276.

Rokitansky's Pathological Anatomy." Vol. II (the first issued), 8vo
pp. 375. ^' '

2

FOR THE SEVENTH YEAR, 1849-50.
The Genuine Works of Hippocrates r Vol. II, pp. 406,
" Essays on the Puerperal Fever, and other Diseases peculiar to Women."
8vo, pp. 552.

" The Works of Sydenham, translated from the Latin." Vol. II, pp. 396

FOR THE EIGHTH YEAR. 1850-1.
" Rokitansky's Pathological Anatomy." Vol. Ill, 8vo, pp. xvi, 467.
" Hunter on the Gravid Uterus:' I vol., folio, 34 plates, with descriptive
letter-press.

FOR THE NINTH YEAR, 1851-2.
" Unzer and ProchasJca on the Nervous System." 1 vol., pp. xvi, 463.
" Annals of Influenza." 1 vol., pp. xvi, 406.
' Eokitansky's Pathological Anatomy." Vol. IV, pp. x, 398.

FOR THE TENTH YEAR, 1852-3.
" Romberg on Diseases of the Nervous System" 2 vols. Vol. I, pp. xvi,

368 ; Vol. II, pp. viii, 450.
' ' Kvllike7-'s Manual of Human Histology." Vol. I, woodcuts, pp. xix

498.

FOR THE ELEVENTH YEAR, 1853-4.
" K(>llike)''s Manual of Human Histology." Vol. II, woodcuts, pp. x,
434.

" Rokitansky's Pathological Anatomy." Vol. I, 2 plates, pp. xvi, 446.
" Dupuytren on Lesions of the Blood-vessels," &c. 1 vol., pp. 378.

FOR THE TWELFTH YEAR, 1854-5.
" WedVs Pathological Histology." 1 vol., woodcuts, pp. xxvi, 637.
" Oesterlen's Medical Logic." 1 vol., pp. xii, 437.

FOR THE THIRTEENTH YEAR, 1855-6.
" Velpeau on Diseases of the Breast." 1 vol., pp. xxiv, 608.
" The Works of Areteeus," Greek and English. 1 vol. pp. xx, 510.

FOR THE FOURTEENTH YEAR, 1856-7.
" Von Sicbold and Kikhenmeister on Intestijial Worms and other Para-
sites." 2 vols., 8vo, with numerous illustrations, plain and
coloured. Pp. xix, 492 — xvi, 287 — xx, 88.

*** Those books to which an asterisk is affixed are out of print ; of the
others copies are still on hand, and may be had at reduced j)rices
on nj)plication at 45, Frith Street, Soho.

I