RECORD OF MEDICAL SCIENCE.
ANATOMY AND PHYSIOLOGY.
JI Retrospect of the progress oj Microscopic Investigation, and of the
more important recent Contributions to Normal and Pathological
Histology. By Robert D. Lyons, M. B., T. C. D., L. R. C. S. I.
Ex-clinical Jlssistant to the- Meath Hospital, one of the Surgeons to
the Anglesey Dispensary, Lecturer and demonstrator of Anatomy in
the original School of Medicine, and Honorary Professor of Anatomy
to the Royal Dublin Society.
Of the several methods of investigation by which, during this, the
first half of the nineteenth century, the science of medicine has been ad-
vanced, and so many important additions have been made to our know-
ledge as well of normal structure and function, as of the several lesions
which are produced in both by disease, not one is entitled to more
serious attention at the hands of the physiologist, the pathologist, and
the practical physician, than that which reveals to us, by the aid of the
microscope, the ultimate configuration and arrangement of the particles
of the most complex tissue, and resolves into elements the most dissimi-
lar what to the naked eye appears a homogeneous fluid.
While we acknowledge the deep debt of obligation which our science
owes to the researches of the chemist, and fully appreciate the value of
his labors, we cannot but think that the extensive and vigorous prosecu-
tion of microscopic investigation is destined to confer equally signal
benefits on medicine. A retrospective glance at what has been already
achieved in this department would appear sufficient to convince even
the most sceptical; but it is to be regretted that an irrational conserva-
tism, and opposition to what is new, with a profound veneration for all
that the past has transmitted to us, are too often active and watchful to
throw a barrier of hostile prejudice in the way of those who are bold
enough to break new ground. We find that, even on the Continent,
very recent writers have thought it necessary to enter at some length
into the consideration of the claims which the microscope has on our at-
tention, though neither amongst our French nor German neighbors can
its application to scientific medical investigation be considered as
new (a.)
And yet, if we are to believe in a gradual progress towards the per-
fection of our art, the new must be ever looked for, and its advent
should be hailed with gladness; not, however, that it may supersede
the old, as proclaimed by many of its too zealous advocates with an ex-
aggerating enthusiasm, perhaps never wholly separable from the intro-
duction of a new dogma; but that with new aids superadded to the means
we are already in possession of, we may be the better able to under-
take the investigation and solution of difficulties that have hitherto baf-
fled our best energies. And who is there so confident in the powers
of his art, that will venture to assert that it needs no amelioration, that
it has reached its point of culmination? If there be such, let him re-
flect on the many occasions that the most scientific principles of diagno-
sis have failed to detect an existing lesion, that the most judiciously di-
rected treatment has been unsuccessful; let him but look on the long
category of nervous diseases, and sum up the amount of his knowledge
of their causation and their pathology, or the value of his skill in their
treatment.
Though our preface be apologetic, it can hardly be deemed superflu-
ous, especially in the pages of an Irish periodical, issued from the Irish
school were every department of medicine is represented, and cultivated
with success, save one, and that one, as we firmly believe, destined to
(a.) Traite du Microscope, &c., par le Dr. Ch. Robin. 8vo. Paris, 1849,
PP- 79, et seq The following passage is deserving of attention :—
“ Il n’y a, comme on le voit, dans tout ce qui prece, rien de plus que ce
que nous etudions dans les autres corps, ce sont les memes characters, les
memes proprietes; il n’y a de nouveau que le maniere des les observer, qui
n’est elle meme qu’une modification de nos moyens ordinaires d’observa-
tion appropiees a leur petit volume.
exercise a powerful influence on our views of the most abstract as well
as the most practical questions. We believe that we are justified in
saying that no original communication of any importance has been made
to histology, or any collateral branch of microscopic investigation, by an
observer from the Irish school; though, as we are fully aware, many of
our physicians and surgeons have occupied themselves in verifying the
observations of others, and in no few instances have acquired practical
skill in the employment of this instrument, and made useful applica-
tions of the results thus obtained in the practice of their profession (a.)
It may, however, be anticipated, that before long the attention of the Irish
school will be fully awakened to the importance of the subject, and that
many will be found .amongst us ready and willing to engage in this
interesting department of medical investigation. Our object in the
present retrospect has been as much to bring the subject prominently
forward, as to give a succinct though brief account of some of the more
remarkable contributions to histology, which have been recently made
in the English and Continental schools. The limited space which can
be afforded to communications like the present in a journal so fully oc-
cupied as this with subjects of a more directly practical nature, prevents
us from giving as complete a resume of the state of microscopical science
as we could wish ; it is to be hoped, however, that the several contribu-
tions to histology that we are about to bring under consideration will
be found both interesting and important.
The systematic treatise of Quekett, which was brought under review
in a former number of this Journal, enters so fully into the considera-
tion of the mechanical arrangements of the microscope, that we feel it
unnecessary to do more at present than refer to its pages such of our
readers as may be anxious to learn any particulars of manipulation. A
work of somewhat similar scope has been published (&.) by M. Chas.
Robin, author of the treatise “ Des Vegetaux qui croissent sur 1’Homme
et les Animaux.”
Though it is no part of our present intention to describe either the
microscope itself or any of its accessory apparatus, we shall borrow
from the treatise of the latter author some practical hints which may be
of value to those who are actually engaged in making investigations.
The experience of M. Robin is directly opposed to the opinion main-
tained by some, that the prosecution of microscopic investigation is in-
jurious to the organs of vision, and he does not hesitate to say, “Depuis
Leuwenhoeck, qui conserva d’excellents yeux jusque dans une extreme
(a.) It is well known to most of our readers that the late Dr. John Hous-
ton? of this city, occupied himself very assiduously at microscopic investi-
gation. Drs. Carte, Aldridge, Hill, Moore, Steele, Fleming, &c. &c., possess
good instruments and are excellent observers. The last-named gentleman
made an interesting communication, on the subject of urinary deposits, to
the Surgical Society, at its last meeting, and has on many occasions favored
us with opportunities of examining the urine in several abnormal condi-
tions.
(&.) Du Microscope et des Injections, par le Dr. Ch. Robin. 8 vo. Chez
J. B. Bailliere, a Paris, 1849.
vieillesse, tous ceux qui se sont beaucoup servis du microscope s’accor-
dent sans exception a reconnaitre que jamais ils n’ont ressenti le moin-
dre trouble visuel.” If we but reflect, as this author remarks further
on, that the light of the microscope is, for the low powers, scarcely
greater than that of the sky or a lamp, by reason of the small degree of
concavity of the reflecting mirror, and that, as we raise the power of the
object-glass, the amount and intensity of the light diminish proportionably,
we see no reason why the habitual use of the microscope should tend
to injure the visual apparatus. At all events, there is no ground for
supposing that the eyes would be more liable to injury from this use of
them, than from constant reading or writing, which are equally fatigu-
ing occupations.
Amongst the embarrassments which the inexperienced microscopic
observer meets with (they have occurred over and over again to the
writer,) may be enumerated his mistaking for constituent parts of the
object he is investigating, the several flaws, scratches, and innumerable
imperfections of the ordinary glass slides, as also the presence of dust
and extraneous matter. Occasionally, when the eye is brought very
near the eye-glass during a protracted and careful examination, the
movement of the lids throws the eye-lashes in front of the pupil, and
they assume the appearance of large filaments crossing the field. But
a source of error much more likely to escape detection will be found in
the so-called globules and filaments of the eye, which do not depend on
a too strong impression of the retina by the rays of light, as supposed
by some, but will be found to exist in both eyes of every individual who
looks through the microscope, being subject to certain varieties in dif-
ferent persons. We are indebted to M. Robin (a.) for a very satisfac-
tory account of this phenomenon, of which we propose freely to avail
ourselves. When we examine the field of the microscope, without pla-
cing an object in focus, a mass of small, perfectly round globules, all
nearly equal in size, may be observed. They cover all parts of the
field, except about a sixth externally, and a space somewhat smaller
within. Two or three tortuous very pale filaments are seen a little ex-
ternal to the centre of the mass of the globules, a few of ihe latter adhe-
ring to them. The mass of globules is limited without by a flattened
line of filament, somewhat brilliant in the centre, appearing of the size
of a demi-millimetre, and either straight or slightly curved. Within it
is limited by a filament more brilliant than the preceding, and remarka-
bly flexuous, and folded on itself. Jill the globules and filaments move
together. There appear to be two planes of globules, the one nearer to
the eye with sharper outline ; the other deeper, paler, more distant, and
with their borders more undefined. These two planes sometimes move
in opposite directions, but only through a small space, and quickly re-
sume their places. They are in constant motion, and may be ascer-
(a.) This writer informs us that M. Donne, in his Cours de Microscopie,
Paris, 1844, in 8vo., has given a very elaborate description of these globules
and fibres. See also Atlas de Cours de Microscopie, Paris, 1845, in fol. pl.
xx. fig. 83.
tained to obey the movements of the head of the observer, remaining
stationary when the latter is fixed for an instant with both hands. The
filament which limits the mass of globules externally can be brought to
the centre of the field, and it may be then seen that there is a certain
number of globules placed outside it. The internal tortuous filament can
also be removed, and then external to it will be seen one or two other
filaments, equally tortuous and brilliant, directed obliquely towards it.
The globules are perfectly round, close to each other, and appear about
a demi-millimetre in diameter. They present in the centre a brilliant
point, surrounded by a dark, well-defined circle, which is itself sur-
rounded by a second and last external concentric ring, as brilliant as the
central point. Those of the deeper plane differ only in being less de-
fined, some of them are in contact with, and impinge on one another,
so that their dark borders touch. Besides these globules, some persons
see others, larger and more transparent, which do not always occupy
the same place in the field of vision. The external straight filament is
brilliant in the centre, the borders being more obscure and less defined :
it appears about one or one and a half millimetres in size, no globules
adhere to it, and it is impossible to say whether it is hollow or full.
The internal filament differs from the preceding only by its flexuosity,
which causes it to occupy more space in breadth but less in length, and
makes it more evident when brought to the centre of the field. The
filaments placed amongst the globules are much more narrow than the
preceding, they are two or three in number, tortuous, and about the
length of a quarter of the field. They are not always so readily per-
ceived as the larger ones, their borders being less marked, and less
brilliant, at the same time that the globules encircle and appear to ad-
here to them. These globules are ordinarily disposed in pairs, and in
contact one with another, each pair, however, being separated from the
next by a certain interval.
It is unquestionably of the highest importance that we should be able
to distinguish these little bodies from any part of the object we are
examining; and, in general, no difficulty whatever will be experienced
in doing so. When we consider that they follow the motions of the
head, and are not affected by changing the positions of the glass slides,
or by any movements communicated to the stage, we see at once that
they must be referred to the eye of the observer. Hence the necessity
on the part of the latter, of making himself thoroughly acquainted with
their figure, position, and the peculiar modification which they may
possibly be subject to in his own person. They have been, and may
be, to many a source of painful apprehension and uneasiness, giving rise
to the opinion that the organs of vision were threatened with disease.
It cannot, therefore, be too generally made known, that the ’phenome-
non is one experienced by all who make examinations with the micro-
scope ; that the conditions that produce it are universal; and that there
is no reason for fearing that cataract, or amaurosis, will be the reward of
patient and protracted microscopic investigation. As to the cause of
these globules and filaments of the eye being seen under the microscope,
much difference of opinion still exists. M. Robin appears to agree with
M. Donne in thinking, that it is in the liquor Morgagni we must look for
their real seat; it would appear to us, however, more probable that they
are due, as remarked by Wallace, to the filaments and globules which
the investigations of Pacini, Treviranus, Hanover, and others, have
proved to exist in the retina. We consider it quite possible that the
posterior wall of the eye may reflect light, and thus give an image of
itself, in the same manner that objects are seen in the bottom of a river
through the water ; that in fact the eye may perform the triple office of
twice transmitting light, bringing it to a focus, and seeing it.
The work of Mr. Quekett contains a very excellent description of
several varieties of micrometers, and gives judicious rules for the esti-
mation, by their assistance, of the value of the magnifying powers of
the different object-glasses.
The two processes hitherto most frequently in use on the Continent
are, according to M. Robin, the method of the camera lucida and double
vision ; which consists in throwing, by means of a camera lucida, the
magnified image of an objective micrometer (whose subdivisions are
known) on a rule divided into millimetres, placed at the distance of dis-
tinct vision. By noting how many millimetres on the latter are covered
by each hundredth of a millimetre of the micrometer, the magnifying
power is thus found directly. The second process consists in looking
with one eye at the subdivisions of an objective micrometer placed under
the microscope, while with the other we regard the divisions of a rule or
the points of a compass. The images of the two objects, painted sepa-
rately on each eye, are thus superposed one on the other in the nervous
centres; and with a little habit, it may be easily ascertained how many
of the subdivisions of the rule are covered by a single division of the
magnified micrometer.
Several sources of inaccuracy are stated by M. Robin to exist in both
these methods ; these he had detailed at length in his work(a); and he
has accordingly proposed the following method by the ocular micrometer,
which appears to answer all requirements, both as to simplicity and
accuracy. It consists in employing an ocular micrometer, the superior
glass of which magnifies exactly ten times. The micrometer placed in
the focus of the superior glass of this ocular is one centimetre or half a
centimetre, of which each millimetre is divided into ten parts. These
tenths of a millimetre, being magnified ten times, equal each a millime-
tre, it is consequently a decimetre, or a demi-decimetre, each of whose
subdivisions is equal to a millimetre, wh’ch is placed permanently in
the ocular. Consequently, if an objective micrometer be placed under
the microscope and that, in examining with the ocular, each hundredth
of a millimetre of the first is magnified so as to cover three divisions of
the second, we learn that the microscope magnifies 300 times.
The following method, which is but a slight modification of that pro-
posed by M. Robin, has been adopted by the writer. It presents the
advantage of great simplicity, and requires the use of only one microme-
ter, and with a little practice will enable the young microscopist to
(a) See his Treatise on the Microscope, pp. 134, 135, et seq.
make himself acquainted with the powers of the several object-glasses
and eye-pieces he may chance to possess ; a knowledge which it is the
more necessary he should be able to procure for himself, as almost all
the instruments in use and on sale in this city are unprovided with any
scale or registered description of the powers of the several glasses. It
will be necessary in all instances to possess an objective or stage mi-
crometer, whose subdivisions are known; with this, an ordinary eye-
piece, and one of the circular glass slips used for covering objects, we
are in possession of abundant means for estimating the powers of the
various object-glasses; and if a little care be used in the manipulation,
a very considerable degree of accuracy may be obtained. The circu-
lar glass slip may be extemporaneously converted into an ocular microme-
ter, by marking off on it, from a rule, with a diamond, or a finely point-
ed pen, any of the smaller subdivisions of an inch. Thus marked, it
may be passed into the eye-piece by unscrewing the ocular, and be al-
lowed to rest on the stop or diaphgram; the ocular being now replaced,
we proceed to ascertain its power, and the consequently increased di-
mensions of the divisions of the glass slip, which may be done in the
ordinary way, by looking at them with one eye, while the other is
thrown on the subdivisions of a rule. These interspaces, being large,
are easily compared, and being superposed one on the other, as above
described, the magnifying power of the ocular is thus obtained. If the
objective micrometer be now brought into focus, we can easily see how
many of its subdivisions correspond to one or more of the spaces which
we have marked off, and the power of the object-glass is thus readily
found.
For low power, and the comparison of tolerably large divisions of the
micrometer and the rule, no difficulty will be experienced in ascertaining
the magnifying number of a particular objector eye-glass, by the method
of superposition, or that of looking with one eye through the microscope,
and with the other at a rule, and at most only a few trials will be neces-
sary in order to attain very considerable accuracy ; but it will be found
widely different when we come to deal with high powers and small di-
visions and hence the value ofM. Robin’s method, and the modification
of it just proposed, in which, though the preliminary step is made by
ascertaining the power of the ocular by a method of double vision,
another and certainly a more accurate process is employed for estima-
ting the power of the object-glasses, which necessitates the comparison
of minute subdivisions, in which, of course, any error would be less
likely of detection. As to any source of error which might possibly
arise from placing a slip of glass between the ocular and field-glass of
the eye-piece, it must be so very triflingas not to deserve any notice.
By selecting a glass whose surfaces are neither convex nor concave, but
as nearly as possible flat, the amount of deviation will be altogether in-
considerable.
By a reference to the tables given in the works of Robin and Quekuett,
it will be seen that the number 800 represents the highest magnifying
power which has been obtained for the object-glass by Nachet, a dis-
tinguished optician of Paris. In this no account is made of the influ-
ence of the eye-glass, which would, of course, add considerably to the
power. While with the one-twelfth inch object-glass, and the eye-
glass A, manufactured by Ross, of London, a magnifying power of 600
is obtained ; the same object-glass, giving with this maker’s eye-glasses
B and C, respectively, 870 and 1400, as the magnifying powers.
With powers far lower than these, however, many of the most useful
and interesting investigations can be made. “ The magnifying powers
from 100 to 300,” says M. Robin, “ serve for studying the bones, the
teeth the hairs, the hair-bulbs, and the glandular culs-de-sac, but only
in what concerns their grouping in each acinus: the study of their
epithelium demands higher object-glasses.” We think, however, that
this author had elsewhere over-estimated the value of the very high
powers, and also the facility of recognizing by their aid, and distinguish-
ing the several varieties of abnormal formation: “ La pretendue im-
possibility de distinguer les globules de pus, des globules blanc du sang
des corpuscules du tubercule et une foule d’autres erreurs, tiennent a la
meme cause (les faibles grossisements)—p. 172.—Dub. Quar. Jour.