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THE AMERICAN JOURNAL
OF
ANATOMY
EDITORIAL BOARD
CHARLES R. BARDEEN G. Cart Huser FRANKLIN P. Mau
University of Wisconsin University of Michigan Johns Hopkins University
Henry H. DonaLpson GEORGE S. HUNTINGTON J. Puayrarr McMurric#
The Wistar Institute Columbia University University of Toronto
Simon H. GaGe Henry McE. Knower, GrEorGE A. PIERSOL
Cornell University Secretary University of Pennsylvania
University of Cincinnati
VOLUME 22
1917
THE WISTAR INSTITUTE OF ANATOMY AND BIOLOGY
PHILADELPHIA, PA.
: oo 5 d
Rates 2 Ra wire
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‘fii ~\h) i ea) ety
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CONTENTS
No. 1. “iUIbY
GerorGceE L. Streeter. The factors involved in the excavation of the cavities in the car-
tilaginous capsule of the ear in the human embryo. Twelve figures................ 1
PesOGK “Onimetopisnr. Nine fAgUreset<.:« ..:....... «0: ceeneeiae clon alnarsiee oldcoe an tt hae eee 27
FRANKLIN P. Matyi. On the frequency of localized anomalies in the human embryos
andumtants at births” Hishteen’ figures... ....:. :. eee. Seo se a ceed eee os eee 49
Ruopa ErpMann. Cytological observations on the behavior of chicken bone marrow
inplasmaimmedium: Pwo text ficuresand tine’ platesssmea. 4.2: 2.0 oss. se eee eee 73
Ivan E. Wain. The relationships and histogenesis of thymus-like structures in Am-
mocuetes.. Three text figures and foursplates...... |... epeeeeee od cc uae seat Gene 127
No. 2. SEPTEMBER
WarrREN H. Lewis AND MARGARET R. Lewis. Behavior of cross striated muscle in tissue
SMUT CK wit OULLECM MONTES .¢ ett Va ak abep iis. s+. . +» <0 8 Se eb Sioielat nee aie 169
J. A. Myrrs. Studies on the mammary gland. 11. The fetal eS eats of the mam-
mary gland in the female albino rat. Twelve figures......... . 195
CHARLES R. STOCKARD AND GEORGE N. PAPANICOLAOU. The Pence Oo. a elena ¢ oes-
trous cycle in the guinea-pig—with a study of its histological and physiological
ehanvess One text figure and mine plates. ..... . ... seein oes 25> see ae 225
H. E. Jorpan anp J. B. Banks. A study of the intercalated dises of the heart of the
Dec wLtrty-OnemeUres (fOUr Plates) s.25 cs... . . dee et noes Gnd Sema GS aigcmeeee 285
No. 3. NOVEMBER
AIMEE S. VANNEMAN. The early history of the germ cells in the armadillo, Tatusia
novemeincta. Three plates and two text figures... sate . d41
KE. A. BAUMGARTNER. The development of the serous clnas (Gon Ebner’ 5) ae ae aie
LAOS Ap Ae HIME AN | EMS tGUTES heats. coos <3 cua ORR eh oie eee esoeitca steers ec 365
JAMES Crawrorp Watt. Anatomy of a seven months’ foetus exhibiting bilateral ab-
sence of the ulna accompanied by monodactyly (and also Diaphragmatic hernia)
Wane ext 1eMres ANG TOUL PIAbES cai os suis « «. SQM ad sine due aka mpee cern a «tee 385
Lesiiz B. Arey. The normal shape of the mammalian red blood corpuscle. One figure 439
ANDREW T. RAsMusSEN. Seasonal changes in the interstitial cells of the testis in the
woodchuck (Marmota monax). Twenty-six figures (three plates)................... 475
ili
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eee ea ~ 6
i apie rae
THE FACTORS INVOLVED IN THE EXCAVATION OF
THE CAVITIES IN THE CARTILAGINOUS CAPSULE
OF THE EAR IN THE HUMAN EMBRYO
GEORGE L. STREETER
Department of Embryology, Carnegie Institution of Washington, Baltimore,
Maryland
TWELVE FIGURES
The main mass of the cartilaginous capsule of the ear matures
into true cartilage when the human embryo reaches a length
of 20 to 30 mm., at which time it has acquired what may be
considered its adult form with characteristic chambers and
openings. From this time on, throughout its whole cartilag-
inous period, and even after ossification has begun, it undergoes
continuous growth, maintaining at the same time, however,
its general form and proportions. Such a growth involves
both an increase in the surface dimensions of the capsule and a
gradual enlargement or excavation of its contained cavities. It
is to the manner in which this excavation is accomplished that
the writer wishes to call attention and particularly to the factors
concerned in its progress whereby a suitable space is always
provided for the enlarging membranous labyrinth. The actual
amount of increase in size of the labyrinth is graphically pic-
tured in figure 1. The outlines are made so that they show on
the same scale of enlargement a series of wax-plate models of
the left membranous labyrinth of human embryos having a
crown-rump length of 20, 30, 50, 85 and 130 mm., as indicated
in the figure. This covers the period during which the otic
capsule is in a cartilaginous state. Ossification begins when the
fetus has attained a crown-rump length of about 130 mm. The
growth from then until the adult condition is reached may be
judged by comparing the above with the final stage, labelled
1
THE AMERICAN JOURNAL OF ANATOMY, VOL. 22, No. 1
sJuLy, 1917
2 GEORGE L. STREETER
adult, which is taken from Schénemann’s reconstruction! and
reproduced here so as to be on the same scale of enlargement as
the younger stages. Since the cartilaginous labyrinth cor-
responds closely in form to the membranous labyrinth, particu-
20mm 30mm. 50 mmi
Yj
85mm ADULT
Fig. 1 Median views of wax-plate models of the left membranous labyrinth
in human embryos having crown-rump lengths as indicated in the figure. The
largest one is taken from Schénemann (’04) and represents the adult condition.
They are all on the same scale of enlargement (4.4 diameters) and thus compari-
son of them shows graphically the amount of growth the labyrinth experiences
during this period.
larly as regards the canals, one can see from figure 1 that there
is & progressive increase in the size of the cartilaginous chambers
throughout the whole embryonic period.
In addition to this increase in size, there is a change in the
form of the cartilaginous labyrinth. The general proportions
1 Schoenemann, A. Die Topographie des menschlichen Gehérorganes. Ver-
lag von Bergmann, Wiesbaden, 1904. Plate 2, figure 20.
EXCAVATION OF THE CARTILAGINOUS OTIC CAPSULE 3
are maintained but there are alterations in the detailed form.
As the canals become larger and longer they describe arcs of
lesser curvature. If one compares the superior canal of an 80
mm. fetus with that of a 30 mm. fetus it will be found that in
the former it has doubled its diameter and trebled its length.
There is, moreover, a constant change in the relative position
of the cartilaginous canals. The lateral canal, for instance,
progressively recedes from the lateral wall of the vestibule. In
studying this canal, therefore, one may know that it is steadily
becoming larger by means of a process of excavation, but this
is so managed that the canal as a whole moves in a lateral direc-
tion through the substance of the cartilaginous capsule. The
topography of the cartilaginous labyrinth is so well provided with
known landmarks that these changes in its size and form can be
accurately followed. It is possible to determine deductively
at what points new cartilage is being laid down and at what
points it is being removed. On this account the cartilaginous
capsule of the ear is a particularly favorable place for determin-
ing the histological features of the growth of cartilage.
As has been noted above the growth of the cartilaginous otic
capsule resolves itself into an increase in its external dimensions
with a simultaneous hollowing out and reshaping of its contained
chambers. It at once becomes evident that this cannot be
accounted for on the basis of a simple interstitial increase in the
mass of cartilage together with its passive rearrangement to
allow for the enlarging cavities, due for instance to a mechanical
expansive pressure from the growing membranous labyrinth
with its surrounding tissue and fluid. Such a passive rearrange-
ment could only occur in a tissue that is very plastic, whereas
cartilage is one of the least plastic of the embryonic tissues.
Moreover the histological picture is not that of mechanical pres-
sure. The cartilaginous chambers are always excavated slightly
in advance of the space actually required by the membranous
labyrinth, and there is no evidence of the labyrinth being
cramped or of the creation of pressure grooves in the margins of
the cartilage. Nor is the situation improved by the introduc-
tion of the conjectured activity of the perichondrium, either in
4 GEORGE L. STREETER
explanation of the deposit of new cartilage or of the excavation
of the old, since the perichondrium, as will be shown, does not
make its appearance until after a considerable amount of the
erowth and hollowing-out of the labyrinth had been already
completed. Therefore there is involved in the development of
the cartilaginous capsule something more than interstitial and
perichondrial growth, in the ordinary sense of the terms. On
account of its bearing upon this problem, it is the purpose of
the present paper to call attention to the occurrence of dedif-
ferentiation of cartilage in the human embryo, and to point out
the important part which this process normally plays in the
hollowing out and reshaping of the otic capsule during its
development.
The term dedifferentiation is applied here in the sense of a
regression of certain areas of cartilaginous tissue to a more
embryonic form, the same areas being subsequently rebuilt or
redifferentiated into quite a different type of tissue. Dedif-
ferentiation is defined by Child as ‘‘a process of loss of differ-
entiation, of apparent simplification, of return or approach to
the embryonic or undifferentiated condition.” In his note-
worthy review of this subject he makes the assertion that the
wide occurrence and significance of dedifferentiation in the
lower animals and plants ‘“‘must at least raise the question
whether similar processes do not occur to some extent in higher
forms.’”? From the context it is evident that he refers to man
as well as other mammals. The materialization of his predic-
tion is here at hand in the development of the cartilaginous
capsule of the ear. Before entering into this further it will be
necessary to outline the earlier steps in the histogenesis of this
particular tissue.
THE THREE STAGES IN THE DEVELOPMENT OF CARTILAGE
The cartilage of the otie capsule in its transition from
embryonic mesenchyme to true cartilage passes through three
fairly definite phases: firstly, the condensation of mesenchyme
*#Child, C. M. Senescence and rejuvenescence. University of Chicago
Press, 1915. Page 293.
EXCAVATION OF THE CARTILAGINOUS OTIC CAPSULE 5
around the otic vesicle; secondly, the differentiation of the con-
densed mesenchyme into precartilage; and thirdly, the conver-
sion of precartilage into true cartilage. These three histogenetic
stages merge more or less diffusely into one another and one
must bear in mind that such a subdivision is necessarily.
arbitrary and tends to result in an exaggeration of the distinct-
ness-of the lines of their demarcation. Their points of dif-
ference, however, are here emphasized because the reversal of
one state of development into a previous state is the feature to
which it is desired to call especial attention.
STAGE OF CONDENSED MESENCHYME
When a human embryo is 4 to 5 mm. long the mesenchy-
mal tissue surrounding the otic vesicle differs very little from
that in other regions. The nuclei, however, are quite sparse
in the regions ventral to the neural tube in the median line, and
they become perceptibly more numerous as one explores later-
ally into the neighborhood of the otic vesicle. This slight in-
crease in the number of nuclei around the vesicle marks the
beginning of the mesenchymal condensation that is to form the
otic vesicle. A definite layer of such nuclei is not found until
the embryo reaches a length of about 9 mm.; it is then possible
to recognize a fairly well outlined zone of mesenchyme which
represents the otic capsule in its first stage of development.
In figure 2 is shown a sketch indicating the relations which
exist at that time. It represents a transverse section through
the otic vesicle at the level of the attachment of the endolym-
phatic appendage. The zone of condensed mesenchyme forming
the primordium of the otic capsule abuts directly against the lat-
eral wall of the vesicle and extends from there to a point about
one-half the distance between the vesicle and the ectoderm. On
the median side of the vesicle this zone is lacking, although there
is a considerable number of mesenchyme cells clustered around
the vascular plexus ensheathing the central nervous system, and
among the nerve rootlets of the acoustic complex. When this
zone is analyzed under higher magnification it is found that it
still consists essentially of a mesenchymal syncytium. It differs
6 GEORGE L. STREETER
morphologically from the adjacent mesenchyme, with which it
is directly continuous, only in its more numerous and more
compactly arranged nuclei and its somewhat richer network of
internuclear processes. ‘This is shown in figure 3 which is
taken from an embryo a little larger than that in figure 2,
but which in its general form is apparently in about the same
stage of development.
Otic capsule
Ectoderm
Otic vesicle
G.petros.
Med. oblong.
Fig. 2 Section through the region of the otic vesicle in a human embryo 9 mm.
long (Carnegie Collection, No. 721) enlarged 66.6 diameters. The primordium
of the otic capsule, consisting of condensed mesenchyme, can be seen enclosing
the vesicle on its lateral surface.
During the period of growth represented by embryos between
9 mm. and 13 mm. long, that is, up to the time when the
semicircular ducts begin to separate from the main labyrinth
through the apposition and absorption of the intervening mem-
branous wall, the zone of condensed mesenchyme around the
otic vesicle increases in extent and compactness, thereby form-
ing a sharply defined capsule which completely encases the
labyrinth. This capsule of condensed mesenchyme has the same
openings and corresponds closely in form to the cartilaginous
capsule into which it is destined soon to be converted.
EXCAVATION OF THE CARTILAGINOUS OTIC CAPSULE it
Otic vesicle
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Fig. 3 Camera lucida drawing of a portion of the otic capsule while it is the
state of condensed mesenchyme. It is taken from a human embryo 13.5 mm.
long (Carnegie Collection, No. 695). The section is 10 microns thick and is
enlarged 950 diameters. The syncytial character of the capsule can be seen
and also its relation to the epithelial wall of the otic vesicle and to the surround-
ing mesenchyme.
STAGE OF PRECARTILAGE
The histogenetic changes which initiate the conversion of the
capsule of condensed mesenchyme into a cartilage-like tissue
make their first appearance just after the separation of the
semicircular ducts from the main vestibular pouch. This occurs
when the embryo is about 14 mm. long. The conversion of the
8, GEORGE L. STREETER
capsule into a true cartilage with a characteristic tinctorial re-
action of its matrix is not completed until the embryo attains
a length of 30 mm. Thus in embryos between 14 and 30 mm.
long the otic capsule consists of a tissue in an intermediate con-
dition between condensed mesenchyme and cartilage. This inter-
Otic capsule
ee Ectoderm
Skull
oe D.sc.post.
ee Sinus tr.
Appendix Gang.nodos.
N. 1X
Fig. 4 Section through the region of the otic capsule in a human embryo 15
mm. long, (Carnegie Collection, No. 719). Enlarged 66.6 diameters. The
epithelial portions of the labyrinth are shown in solid black and it will be noted
that they are in direct contact with the substance of the capsule; there is as yet
no periotic reticular tissue. The section passes through the superior and pos-
terior semicircular ducts and through the utricle near its junction with the
crus commune.
mediate form is known as precartilage. It constitutes the second
of our three stages of cartilaginous growth.
The general form and relations of the otic capsule at the begin-
ning of its conversion from condensed mesenchyme into precar-
tilage is shown in figure 4, which represents a horizontal section
through this region in a human embryo 15 mm. long (Carnegie
EXCAVATION OF THE CARTILAGINOUS OTIC CAPSULE 9
Collection, No. 719). It will be noted that the capsule abuts
directly against the epithelial wall on the labyrinth. Around
the margins of the capsule there is a vascular network the
branches of which, however, do not penetrate into its sub-
stance. In its form it is essentially the same as its antecedent
capsule of condensed mesenchyme, but in structure it can be
seen to be undergoing certain characteristic alterations. These
do not oceur uniformly throughout its substance but appear
Fig. 5 Camera lucida sketches showing characteristic fields in sections of the
otic capsule while it is in the precartilage state. Enlarged 950 diameters. The
groups labelled A are taken from an embryo 17 mm. long (Carnegie Collection,
No. 576). Group B is taken from an embryo 18 mm. long (Carnegie Collection,
No. 409).
earlier in some areas than in others. They consist of an increase
in distance between the nuclei, together with an alteration in
the internuclear protoplasmic network and its spaces. Whereas
the capsule, as seen in prepared sections, has previously con-
sisted of a mesenchymal syncytium, it now gradually loses its
syncytial appearance. Most of the branching processes dis-
appear and are replaced by a homogenous mass. Some of the
processes, on the other hand, persist, and become thicker and
more sharply outlined. These persisting larger processes ustially
exhibit a characteristic relation to the nuclei. Two or more of
10 GEORGE L. STREETER
them unite in the formation of a loop at one side or at one or both
ends of a nucleus, thereby creating a perinuclear space which
soon takes on a more transparent appearance than the surround-
ing homogeneous material that accumulates in the place of the
disappearing processes. These changes can be seen in the
sketches shown in figure 5, which represent characteristic
areas in the otic capsule while in the precartilage stage in
human embryos 17 and 18 mm. long. In the two sketches
marked A the contrast beween the permanent and disappearing
protoplasmic processes is already noticeable. In the sketch
marked B the transition is more advanced although one can still
recognize in the homogeneous matrix remnants of branching
processes which have not yet disappeared. The persisting
processes enclose characteristic capsular or perinuclear spaces.
Similar spaces are shown in figure 6 which presents a series of
isolated nuclei with their associated permanent processes such
as are found in sections of maturing precartilage. In some of
these (figure 6, C and figure 5, B,) there is a beginning accumu-
lation of granular protoplasm at the margin of the nucleus which
constitutes the so-called endoplasm and becomes enclosed with
the nucleus in the capsule. After the formation of the spaces the
endoplasm gradually accumulates and forms the cell body of the
encapsulated nucleus. Thus in precartilage we find all stages
in the transition, from a mesenchymal syncytium to a tissue
consisting of partially encapsulated cell-islands separated from
each other by a homogenous matrix.
CARTILAGE STAGE
The transition from precartilage into cartilage gradually takes
place in the otic capsule when the embryo is between 25
and 30 mm. long. This maturation is characterized by an in-
crease in the amount of matrix combined with a more complete
encapsulation of the nuclei, or cartilage-cells, as they may now be
designated. With the increase in the amount of the matrix
there is also a change in its chemical composition, so that it
becomes possible to stain it differentially. This tinctorial re-
action constitutes an arbitrary point at which it may be said
EXCAVATION OF THE CARTILAGINOUS OTIC CAPSULE 11
that the precartilage becomes cartilage. In embryos 30 mm.
long the greater portion of the otic capsule reacts tinctorially and
has the histological character of young cartilage. With this
stage we reach the third and final phase of the process with which
we are dealing. The further changes from younger cartilage to
Fig. 6 Characteristic precartilage cells showing the manner in which spaces
become enclosed around them, eventually becoming encapsulated cells of true
cartilage. Enlarged 950 diameters. Group A is from the otic capsule of an
embryo 17 mm. long (Carnegie Collection, No. 296); Group B is from an embryo
24 mm. long (Carnegie Collection, No. 455); and Group C is from an embryo 23
mm. long (Carnegie Collection, No. 453).
older cartilage, and the conversion of cartilage into bone, are
doubtless a continuation of the same general process but in the
present paper they will not be taken into consideration.
PERIOTIC RETICULUM
It has been pointed out elsewhere by the writer’? that there
is derived from the condensed mesenchyme surrounding the otic
capsule not only the cartilaginous capsule but also the periotic
3 Streeter, G. L. The development of the scala tympani, scala vestibuli and
perioticular cistern in the human embryo. Am. Jour. Anat., vol. 21, 1917.
12 GEORGE L. STREETER
reticulum which eventually intervenes between the capsule and
the epithelial labyrinth. The relation existing between this
reticulum and the three stages of cartilage that have just been
defined must therefore now be referred to. The formation of
the periotic reticulum is first indicated by a cluster of deeply
stained nuclei that can be seen along the central edge of the
semicircular ducts in embryos soon after the ducts are formed,
and at about the time the otic capsule begins to change from
condensed mesenchyme into precartilage. These nuclei con-
stitute a focus at which the development of the reticulum and
its blood vessels takes origin. Here the tissue of the capsule
gradually takes on an appearance less like a cartilage-forming
tissue and more like embryonic connective tissue. Spreading
from this focus a narrow area is established which soon encircles
the semicircular ducts and becomes the open-meshed vascular
reticulum which in embryos 30 mm. long everywhere bridges
the space existing between the epithelial labyrinth and the sur-
rounding cartilage.
While in the stage of condensed mesenchyme and in the earlier
part of its precartilage period the tissue of the otic capsule to
all appearances abuts directly against the epithelial wall of the
labyrinth as shown in figures 2, 3 and 4. It is possible, how-
ever, that some of the cells directly adjacent to the epithelium
do not properly belong to the tissue of the otic capsule. It is
conceivable that such cells may represent indifferent mesenchyme
and perhaps angioblasts which were originally enclosed, along
with the otic vesicle, by the condensed tissue of the capsule
where they remain in contact with the epithelial wall in a resting
condition until the embryo attains a length of 20 mm. We
might regard as an indication of their resumed activity the forma-
~ tion of the deeply stained foci along the central margins of the
canals which have been described above. It might thus be
maintained that the periotic reticulum is derived from a few
predestined mesenchyme cells which after a latent period undergo
proliferation and occupy the space vacated by the receding pre-
cartilage. On the other hand one may also maintain that the
reticulum is derived from cartilage-forming tissue; that it is not
EXCAVATION OF THE CARTILAGINOUS OTIC CAPSULE Te
a predetermined tissue but is simply precartilage that has under-
gone dedifferentiation. In the early stages when only a few cells
are concerned this matter cannot be so well determined, the
histological difference between early precartilage and indifferent
mesenchyme cells not being sufficiently great for their certain
recognition. In the later stages, however, it is quite evident
that precartilage tissue is actually converted into a reticulum,
and that the replacement of precartilage by a reticular connective
tissue is accomplished by a process of dedifferentiation. By
identifying a special area through its relation to a particular
canal, and comparing this selected area in a series of stages, it
is possible to observe the conversion of precartilage into re-
ticulum, and to trace histologically step by step the manner in
which a space occupied by precartilage in a younger stage is re-
placed by a reticulum in an older stage. This is the same pro-
cedure which occurs in the conversion of cartilage into pre-
cartilage and in the latter case, on account of the more highly
specialized structure of the tissues, the picture is even more
striking, as will be seen in the following outline in which the
main features of the process will be pointed out.
DEDIFFERENTIATION OF CARTILAGE
It has been noted that in embryos 30 mm. long the main
capsular mass consists of true cartilage possessing encapsulated
cartilage cells and an intervening matrix that is differentially
stainable. A section passing transversely through the lateral
semicircular canal of an otic capsule of this age is shown in
figure 7. This, and figures 8 and 9, form a series showing at
the same enlargement the same canal, i.e., lateral, cut in the
same plane at three successive stages in its development. A
direct comparison of these figures can thus be made and there
is thereby seen the histological changes that occur with the growth
of the canal. The successive figures may be superimposed
upon each other and in this way the relative amount and position
of the constituent tissues be determined. When this is done
it is found that in the process of enlargement the true cartilage
around the margin of the canal becomes replaced by precartilage
14 GEORGE L. STREETER
and the precartilage in its turn becomes converted along its
inner margin into the reticular mesenchyme which finally be-
comes the periotic reticulum. In other words, cartilage of the
third stage as above described, reverts or is dedifferentiated
into cartilage of the second stage and this in turn is dedifferen-
Ductus semicire. lat.
Fig. 7 Section passing transversely through the lateral semicircular canal in
a human embryo 30 mm. long (Carnegie Collection, No. 86), enlarged 100 di-
ameters. The canal at this time is only slightly larger than the contained epi-
thelial duct, but the zone of temporary precartilage marks out an area that is
soon to be excavated by the process of dedifferentiation through which it be-
comes converted into a reticular connective tissue.
tiated into a tissue approximating the first stage. It is this ret-
rogressive adaptability of its tissues combined with their pro-
gressive development which render possible the enlargement of
the otic capsule and the alteration in form and position of its
contained cavities.
In the 30 mm. embryo shown in figure 7, the first of these
three figures, it will be seen that the epithelial duct is sep-
EXCAVATION OF THE CARTILAGINOUS OTIC CAPSULE 15
arated from the main cartilaginous mass of the capsule by a
surrounding zone of precartilage and intervening between the
latter and the duct is a narrow zone of mesenchymal tissue
which is somewhat reticular in character. This zone of reticulum
has attained its greatest width on the median side of the duct,
toward the right, being at this point about twice as wide as the
semicirc. lat.
De ets a)
Ductus
Reticulum
Fig. 8 Section passing transversely through the lateral semicircular canal
in a human fetus 43 mm. long (Carnegie Collection, No. 886). Enlarged 100
diameters. The epithelial semicircular duct is larger in diameter than the one
in figure 9, but that is the accidental result of its having been fixed while in a
distended condition. The size of these ducts cannot be compared without tak-
ing account of this variation in their distension. ~
thickness of the duct wall. It is characterized by its reticular
arrangement and by the presence of small blood vessels which
are not found in the precartilage, although they lie closely against
its inner margin. The area of precartilage stands out con-
spicuously in material that has been intensely stained in hema-
toxylin without any counter-stain. A series of this kind is rep-
resented by No. 199 in the Carnegie Collection. In that series
16 GEORGE L. STREETER
the true cartilage is deep blue on account of the avidity with
which its matrix takes the stain, whereas the precartilage shows
only a nuclear stain and therefore is only faintly colored, as
compared with the sharply demarcated and almost opaque car-
tilage surrounding it. The negative of this picture is presented
in material where there has been an intense nuclear stain with
subsequent decolorization of the cartilaginous matrix. Such a
condition exists in figure 7 but is more marked in specimens
where the stain is more intense, such as the series No. 972 of the
Carnegie Collection. Under such circumstances the area of pre-
cartilage appears as a dark field in the midst of the faintly
stained true cartilage. Depending upon the management of the
technique it is thus possible in embryos about 30 mm. long to
display the future cartilaginous canals; that is, the precar-
tilaginous areas which approximately correspond to them, either
as dark fields in a light background or as light fields in a dark
background.
In the second figure of the series, figure 8, the area repre-
senting the future cartilaginous canal, is appreciably larger.
Its perimeter, compared with that of the canal in figure 7, is in
the proportion of 152 to 115, which are measurements in milli-
meters made on photographs taken at 100 diameters. By com-
paring the two figures it will be seen that the increase in size is
obtained by the encroachment of the precartilaginous area upon
the surrounding cartilage. The amount of this encroachment
represents the amount of true cartilage which has reverted or de-
differentiated into precartilage. In a similar manner the retic-
ular zone surrounding the membranous duct has enlarged at the
expense of the precartilage. The reticular zone as shown in this
figure, taken from a human embryo 43 mm. long, forms a distinct
and characteristic eccentric vascular field, but it undergoes its
greatest expansion soon after this period.
In the 50 mm. embryo, as can be seen in the third figure of
this series, figure 9, the area of the reticular zone is about the
same in size as the whole precartilage area in the 30 mm.
embryo of figure 7. On comparing these two figures it becomes
apparent that there is just as much, and even more, precartilage
EXCAVATION OF THE CARTILAGINOUS OTIC CAPSULE 17
in the latter but it has moved outward into the area that was
previously true cartilage. At this period the outer perimeter
of the precartilage is 192 mm. as compared with 115 mm. in
figure 7. As the old area of precartilage disappeared, a new and
more peripheral area became established. Thus it may be seen
Ductus semicirc. lat.
eticulum
Fig. 9 Section through the lateral semicircular canal in human fetus 50
mm. long (Carnegie Collection, No. 95). Enlarged 100 diameters. This sec-
tion is taken at the same relative position and at the same enlargement as those
in figures 7 and 8, so that they may be directly compared. It will be seen that
the area of precartilage in figure 7 is now entirely replaced by reticulum, where-
as a new and more peripheral area of precartilage has formed at the expense of
surrounding cartilage. This more peripheral precartilage likewise in the end
becomes reticulum.
that true cartilage has been dedifferentiated into precartilage
and this in turn into the periotic reticulum. It is in this way
that the enlargement of the canals is accomplished, a process of
excavation based on the dedifferentiation of a specialized tissue
into a more embryonic type, followed by a readjustment of re-
differentiation of this simpler form into a tissue adapted to the
new conditions.
THE AMERICAN JOURNAL OF ANATOMY, VOL. 22, NO. 1
18 GEORGE L. STREETER
In addition to the excavation of cartilage there occurs, in
connection with the growth and alteration of form of the otic
capsule, the deposit of new cartilage. As the lateral cartilaginous
canal, for instance, enlarges it also moves laterally, so that the
distance between it and the cartilaginous vestibule increases,
thereby producing a lateral migration of the space as a whole.
Such a migration must involve an excavation of the established
cartilage on its lateral margin and the formation of new cartilage
on its median margin. Therefore on the lateral margin we find
true cartilage being dedifferentiated into precartilage and on
the median margin precartilage being differentiated into true
cartilage. The margins of the cartilaginous canals throughout
the whole embryonic period are in an unstable condition and are
constantly undergoing changes. These are either in the nature
of a uniform excavation throughout their whole contour, re-
sulting in a simple enlargement of the canal, or of an excavation
in certain parts combined with a deposit of additional cartilage
in others resulting in a change of form and position of the canal.
On account of the well defined landmarks that characterize
the labyrinth, it is possible to orient points at which excavation
and new deposit respectively are occurring. Thus one can follow
the histological phenomena of these two processes with great ac-
curacy. Where new cartilage is being deposited, the tissue shows
all the stages of development from an embryonic connective tissue
on its central margin through an area of precartilage to a true
cartilage on its more peripheral margin. These different grades
merging into one another repeat stages which characterized the
whole capsule in embryos between 14 and 30 mm. Where
the cartilage is undergoing excavation the same _ transitions
exist, but the changes are more abrupt and there is a sharper
line of transition between the different zones. The width, how-
ever, and the sharpness of the zones vary somewhat, being
relatively wider and less abrupt in younger stages and becoming
narrower and more abrupt in their transition in older fetuses.
It is quite possible that these changes occur in waves and when
the zones are wider and less abrupt it is due to the greater activity
of this process of dedifferentiation and when the zones are nar-
EXCAVATION OF THE CARTILAGINOUS OTIC CAPSULE 19
rower and more sharply outlined, as is common in older fetuses,
the alteration is then proceeding more slowly.
The dedifferentiation of cartilage into precartilage involves
first of all changes in its matrix including the loss of its tinctorial
reaction, a decrease in its amount and an alteration in its struc-
tural appearance, in that it becomes less homogeneous and begins
to show the presence of branching processes. As a result of
these changes in the matrix, the encapsulated cartilage cells
come to he closer together, pressing to some extent directly
against each other. The combined edges of the overlapping
margins of flattened capsules give the appearance of wavy re-
fractile lines running through the transition zone parallel to the
margin of the canal. With these changes the capsules of the
cartilage cells rapidly become incomplete and take on the appear-
anee of branching processes. With the disappearance of the
capsules the tissue assumes the appearance of a mesenchymal
syneytium which then takes on a reticular character and becomes
part of the general periotic reticulum. The question as to whether
there is an active proliferation of the nuclei in the tissues
subsequent to their alteration from cartilage to precartilage has
not been definitely determined. The material at hand is in-
adequate for a satisfactory solution of this point, although in
some specimens there seems to be an increase in the number of
nuclei in the transition zones of precartilage, over and above
the apparent increase associated with the absorption of the inter-
vening matrix, which could only be explained in that way. It
would seem very probable that with its dedifferentiation there
should be associated a renewed proliferative vitality of a given
embyronic tissue, sufficient at least for its reconstruction into
the newer form.
DEVELOPMENT OF THE PERICHONDRIUM
In studying the cartilaginous canals one must take into con-
sideration the perichondrium and its relation to the continual
transformations occurring along their margins. Reasoning from
the prevailing conceptions, concerning the activity of periosteum
in bone growth, one might expect to find in the perichondrium
20 GEORGE L. STREETER
an important factor in the growth and changes in the cartilage.
In later periods its influence on cartilaginous changes cannot be
easily determined, but fortunately for the solution of this point
it happens that the perichondrium is late in making its appearance
and therefore cannot take any part either in the deposit of new
cartilage or in the excavation of the old until after a considerable
part of this transformation is already completed.
The zone of precartilage surrounding the margins of the
canals in embryos about 50 mm. long might be mistaken for
perichondrium, such for instance as is shown in figure 9. If
this area, however, is followed to a slightly older stage it will
be found to be converted almost entirely into reticulum. The
section shown in figure 10 is through the posterior semicircular
canal of an embryo of the same length, 50 mm., but a little
older in development. It is just at this age that precartilage
very rapidly reverts to reticulum, much more rapidly than the
surrounding cartilage in reverting to precartilage; and therefore
in sections at this period we find only a thin rim of precartilage
around the margins of the canals. The real perichondrium
makes its first appearance when the fetus has reached a length
of about 70 mm. A photograph of a section of the posterior
semicircular canal of a fetus 73 mm. long (Carnegie Collection,
No. 1373) is shown in figure 11. Examination of this section
reveals along the outer margin of the periotic reticulum a conden-
sation of its trabeculae resulting in the formation of a thin fibrous
lamina or membrane near the margin of the cartilage.
This is the perichondrium in its early form. It does not abut
directly against the cartilage but is separated from it by a zone of
transition tissue which consists partly of precartilage and partly
of reticulum. This transitional precartilage-reticular zone, be-
comes narrower and more abrupt in later stages. In all of the
specimens studied, however, it was found intervening between the
perichondrium and the surrounding cartilage. It will thus be seen
that the perichondrium is a derivative of the periotic reticulum.
It forms an outer limiting membrane along the cartilaginous
margin of the latter in a manner somewhat similar to that in
which the membrana propria forms an inner one along its epithe-
EXCAVATION OF THE CARTILAGINOUS OTIC CAPSULE ral
lial margin. The relation of the perichondrium to the reticular
tissue surrounding the labyrinth, as seen under higher mag-
nification, is shown in figure 12. The section is a portion of
the one shown in figure 11 and includes the successive strata
Ductus semicirc. post.
Fig. 10 Section through the posterior semicircular canals in a human fetus
52 mm. long (Carnegie Collection, No. 96). Enlarged 100 diameters. Here the
replacement of precartilage by reticulum has been more active than that of
cartilage by precartilage so there remains only a narrow zone of the latter. The
reticulum begins to show an alteration in its trabeculae. Due to the retraction
and rearrangement of the protoplasm of some of the trabeculae there results a
coalescence of adjacent intertrabecular spaces. There are thus formed larger
fluid spaces that are devoid of traversing trabeculae. As yet there is no
perichondrium.
from the epithelial wall of the labyrinth to the true cartilage.
It will be seen that the membrana propria consists of a narrow
meshed syncytium, such as is found in embryonic fibrous con-
nective tissue, and constitutes a supporting coat for the epithelial
wall of the semicircular duct. The main part of the periotic
connective tissue consists of a wide-meshed reticulum and arbor-
22 GEORGE L. STREBTER
izing through it are the loops of small blood vessels. The peri-
chondrium forms in the outer part of this reticulum as a compact
fibrous membrane. Peripheral to the perichondrium the tissue
is still of a reticular type but passes in rapid transition into pre-
rartilage and then into a true cartilaginous tissue.
After making its first appearance, the perichondrium rapidly
becomes more conspicuous. In fetuses 80 mm. CR length (Car-
7
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yy Sgt ete om PR Ne
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Perichondrium
Fig. 11) Photograph of section through the posterior semicircular canal in a
human fetus 73 mm. long (Carnegie Collection, No. 1373). Enlarged 100 di-
ameters. It shows the perichondrium in its earliest form.
negie Collection, No. 172) it consists of a dense fibrous coat more
than twice as thick as that shown in figure 12. It is clearly
separated from the cartilage by a narrow zone of transitional
precartilage-reticular tissue. In slightly older fetuses, 85 mm.
CR length, (Carnegie Collection, No. 1400-30) it has become a
dense broad zone separated from the surrounding cartilage only
by a narrow cleft of transitional tissue which still, however, can
be recognized as reticular in character. In fetuses 130 mm. CR
long (Carnegie Collection, No. 1018) the perichondrium presents
EXCAVATION OF THE CARTILAGINOUS OTIC CAPSULE 23
arelatively mature appearance. As observed under lower magnifi-
cations, one is apt to conclude that the perichondrum is in direct
contact with the true cartilage. Under higher powers, however,
a narrow zone of transitional precartilage can be seen intervening
between them. In this dedifferentiating zone the matrix has
largely disappeared and the cartilaginous capsules have collapsed
and are flattened out. Thus the elongated endoplasm of adjacent
eartilage cells is brought into contact, being separated only by
Perichondrium
Precart.-retic.
Cartilage
Fig. 12 Detailed drawing of a portion of the same section shown in figure 11.
Enlarged 500 diameters. It can be seen here that the perichondrium is a con-
densation of the meshes in the peripheral part of the periotic reticulum and that
it separated from the true cartilage by a transitional area of precartilage and
reticulum,
24 GEORGE L. STREETER
the remnants of the capsular margins. The appearance of activ-
ity in this zone corresponds to the unstable condition of the
margin of the cartilage which is still undergoing gradual ex-
<avation.
SUMMARY
From a study of the development of the cartilaginous capsule
of the ear in human embryos it is found that the changes in
size and form which it undergoes during its development are
accomplished in part by a progressive and in part by a retro-
gressive differentiation of its constituent tissues. Throughout
the entire period of growth, as far as material was available for
study, it was found that the margins of the cartilaginous cavities
undergo a process of continual transformation. They exhibit
a state of unstable equilibrium, in respect to the opposing tend-
encies toward a deposit of new cartilage on the one hand and
toward the excavation of the old on the other. The margins
thereby are always either advancing or receding and in this
way are produced the progressive alterations in their size, shape
and position. In this manner a suitable suite of chambers is
always provided for the enlarging membranous labyrinth.
The general tissue mass of the otic capsule during the period
represented by embryos from 4 mm. to 30 mm. long passes
through three consecutive histogenetic periods, namely, the stage
of mesenchymal syncytium, the stage of precartilage and the
stage of true cartilage. In the subsequent growth of the capsule
it is found that in areas where new cartilage is being deposited
the tissues of the areas concerned follow the same progressive
order of development. In areas, however, where excavation
occurs, where cartilage previously laid down is being removed,
it is found that the process is reversed. The tissue in such areas
returns to an earlier embryonic state, that is 1t undergoes de-
differentiation. Tissue that has acquired all the histological
characteristics of true cartilage can thus be traced in its reversion
to precartilage and from precartilage in turn to a mesenchymal
syncytium. In the latter form it redifferentiates into some
EXCAVATION OF THE CARTILAGINOUS OTIC CAPSULE 29
more specialized tissue—in this case for the most part into a
vascular reticulum.
The perichondrium is a derivative of the periotic reticulum
and forms an outer limiting membrane along its cartilaginous
margin. During the foetal period the perichondrium does not
rest directly against the true cartilage but is separated from it
by a zone of transitional tissue consisting partly of precartilage
and partly of reticulum. This transitional zone intervening
between the perichondrium and the surrounding cartilage was
observed in all of the specimens that were studied, which includes
fetuses up to 130 mm. CR length. Owing to the fact that the
perichondrium is late in making its appearance, being first seen
in fetuses about 70 mm. long in can take no part in the early
changes in the cartilaginous capsule either as regards deposit of
new cartilage or the excavation of cartilage that had been
previously laid down.
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ON METOPISM
L. BOLK
Director of the Anatomical Institute, University of Amsterdam
NINE FIGURES
It is a well-known fact that in man the two frontal bones
in a certain number of individuals do not coalesce. In normal
circumstances the frontal or metopical suture begins to disap-
pear during the last quarter of the first year, and is completely
closed before the end of the second year, the anterior fontanelle
disappearing during the third year. The phenomenon of a
persisting frontal suture generally is designed as metopism.
Many publications on metopism are contained in the anthro-
pological and anatomical literature. Several reasons have in-
duced me to add the present paper to them. Firstly, I am able
to deal with data unknown till now regarding the numerical oc-
currence of the phenomenon in Dutch skulls. Such a communi-
eation is not wholly superfluous because the frequency of metop-
ism varies not inconsiderably among different peoples or races.
The second reason for the publication of this paper is given by
the fact that in many points the results of my investigations con-
tradict those of other investigators, and, as to the etiology of the
phenomenon, I differ from the current opinion. Commonly an
increased intracranial pressure, caused by the somewhat more
strongly developing frontal brain, is regarded as the mechanical
factor preventing the fusion of the two frontal bones. So Martin
in his Manual of Anthropology says:
Allthis shows that a more considerable growth of the frontal cerebrum,
as occurring in some brachycephalic groups, is to be considered the cause
of metopism. By the internal pressure the normal concrescence of the
frontal bones is prevented, likewise in hydrocephalic skulls, in which
regularly the metopical suture persists.
27
28 L. BOLK
After having communicated the results of my own investiga-
tion I will enter into some critical remarks upon this opinion.
The above mentioned explanation of metopism gives rise to
a more extended point of view. Some authors believe that a
large brain indicates intellectual superiority. And it is easy to
understand that to such a metopical suture too, should be a symp-
tom of such a superiority, being a suture caused by a strongly
developed brain. This opinion has in fact the approval of
Schwalbe. In an investigation into the occurrence of a frontal su-
ture in apes and monkeys this author, after having mentioned the
current opinion with regard to the etiology of metopism, says:
“This hypothesis agrees with the idea that persons with metop-
ical crania are to be considered as being intellectually on a higher
level.”
The partisans of this hypothesis surely may advance the fol-
lowing anthropological fact, in favor of their view. It is incon-
testable that metopism occurs more frequently in culture races
than in those possessing a lower degree of civilization. The
differences are sufficiently pointed out in the following table,
most of whose data are taken from Martin’s Manual of
Anthropology.
Frequency of metopism
per cent
WASUUS (eA ANT I es 28 tc « Sates tc ea WR eens ON RRS ce othr Caley ste Datta se 1.0
ING OER arereas Steer Seo so aR UR TE es CURA Sect enh oe aa 2
Milailanyeinibin st e252. oc. 15 ce RPE ORR Ne SCENE one ee aan eed tay 2 Ra 2.8
(IP SapoUle ee Series! x a. cess <p RR: hy ooo oe SR coe ee ee 4.3
RSLIEAY - Sih 8 6 Pare A RS OR aera a A UMN Tih pt TC Cd 6.4
VALS ANUS RRR eice.cse oocl nox oot ER oe ee OO eee 6.5
IDB eV ENTST AINSI A ae eo eck sac! Oe ORR RR eo aoe ee a 6.4
SIWASB EPR R eats el sw. Oa Win Gey RRs Ln iL cAMP REC RD ee te ome Call
IER epriallo UOC Tees ache sje =! 5! sje RS ie RO ed Ae A en 9.5
RSIGKON (Gab ays NOW. 2 Ane OR re Aes ne ee ieee WR teste 9.5
Patrician pact: Pec saosin ss Caco ako Pte cee Ste en ee ORG
The difference between the civilized and uncivilized peopie
is avery obvious one. And even when rejecting the hypothesis
of any relation between metopism and intellectual development,
this difference still retains its anthropological significance to the
full.
ON METOPISM 29
Furthermore it is clear that even among the Europeans the
ratio is not at all constant in crania of.the inhabitants of the Mid-
European region (Bavarians, Alsatians and Swiss), and in the Slavs
the frontal bone seems to be divided less frequently than n crania
of the inhabitants of the North-European regions (Hamburgher,
Seotch, and, as will be demonstrated further on, also Amsterdam-
ian). I draw special attention to this fact, which does not agree
with the not seldom expressed contention, that metopism occurs
more frequently in brachycephalic than in dolichocephalic skulls.
As far as I am aware, it was Welcker who first pointed out this
idea. And it is found in most treatises on metopism. But I
think in most of these it is a mere statement of a current opinion,
and not a result of definite investigation. The results of research
do not confirm this hypothesis. This will be demonstrated by
my own research in the course of this paper, and the investiga-
tions of Bryce on Scottish crania give similar results. As is well
known these are very dolichocephalic, and yet the author found
9.5 per cent metopical skulls among them. ‘Therefore among
the dolichocephalic Scotchmen the metopical skulls are more nu-
merous than is the case among the more broad-headed inhab-
itants of the Mid-European region. This contradicts the
assumed prevalence of metopism in brachycephalic skulls.
Before finishing these introductory remarks it is necessary to
give a brief account of some of the principal points in the com-
parative anatomy of the frontal suture. A knowledge of these
points is necessary for the thorough understanding of my expla-
nation of metopism, which, as already mentioned, differs from the
current one. That the frontal bone in the human embryo arises
by two points of ossification situated symmetrically is due to the
fact that originally this bone was a paired one. As a rule this
condition persists not only in the lower vertebrates, but even
among mammals there are many groups in which the metopical
suture does not disappear. In Prosimiae as a rule the frontal
suture persists as long as the other sutures of the skull. In case
of an early closure of the system the frontal suture also disappears
early, in case of a persistence of the system till an advanced
age, the frontal suture also persists. There is considerable va-
30 L. BORK
riability as to the age at which the skull bones unite in Prosimiae.
In monkeys the ossa frontalia unite and a persisting metopical
suture is an individual and rare exception. Finally, in Anthro-
poids a metopical suture in an adult skull has never been seen.
The history of the metopical suture therefore is a somewhat
complicated one. Originally the suture was always present,
later it disappears, and finally in man it reappears as a not in-
frequent variation.
I wish to emphasize, that in consequence of this behavior of
the frontal suture in the course of evolution, two possibilities
must be taken into consideration when trying to account for
its reappearance in man. Firstly this reappearance can be ex-
plained as due to a quite new influence acting only in man, namely
the increased development of the brain which prevents the two
frontal bones from uniting. But there is another point of view
of a more physiological nature, claiming our full attention in no
lesser degree. In primitive Primates the metopical suture per-
sisted. In the further course of evolution certain causes, to which
I intend to return, exerted their influence in such a way that both
frontal bones were compelled to unite and the metopical suture
disappeared. Now, I believe, the possibility presents itself that
the metopical suture in man reappears, Just because the factor,
which once caused its disappearance in monkeys, no longer
exerts its influence in the human skull. From this point of view
the problem has not yet been examined.
In the foregoing it is made clear that the metopism of the
human skull is the starting point of some very interesting prob-
lems, to which I will shortly refer in the order in which they are
treated on the next pages. Firstly the question about the fre-
quency of the anomaly in Dutch skulls will be discussed, then
the question whether the metopical suture occurs more frequently
in brachycephalic skulls, and whether it is true that a persisting
frontal suture is of some influence upon the shape of the skull.
Thereupon we will examine if there exists any relation between
metopism and intellectual development, particularly if it is true
that the anomaly is more frequent in large skulls, containing a
ON METOPISM oi
heavier brain than usual, and finally we will enter into the ques-
tion of the aetiology of metopism in men.
The material I used for this research consists of 1400 adult
skulls of inhabitants of Amsterdam who died during the second
half of the last century. It was gathered from one of the ceme-
teries of this town.
In this collection I found 134 skulls with a persisting metop-
ical suture, that is 9.5 per cent. This relation equals that
found by Bryce in Scottish skulls and by Simon in Hamburghian
skulls, and agrees nearly with that found by Broca among the
old Parisian skulls.
As mentioned in the introductory remarks, it is often claimed in
the literature that the metopical suture occurs more frequently
in brachycephalic than in dolichocephalic skulls. Now, we will
examine in the first place whether this statement agrees with the
results of my own research. As a dolichocephalic skull I mean
in the following pages all those with an index cephalicus lower
than 80, omitting therefore a more detailed classification in meso-
cephalic, hyperdolichocephalic, ete.
The number of brachycephalic crania present in the whole
collection of 1400 skulls, amounted to 420, or just 30 per cent,
and among the 134 metopical skulls, there were 55 or 41 per cent
brachycephalic. The number of brachycephalic skulls among
metopical crania surpasses, therefore, that among the collection
as a whole and the difference of 11 per cent really seems to be
very considerable. Only the fact merits mention that the abso-
lute number of metopical skulls (134) is a relatively small one,
and hence a few skulls more or less exert a perceptible influence
upon the percentage. Altogether the above described relation
proves that the majority of the metopical skulls is not brachyce-
phalic. And therefore I do not agree with the statement of
Anntchin that ‘‘metopical dolichocephalie skulls are relatively
rare.” This conclusion, moreover, does not agree with the re-
sults of the investigation of Bryce who, among his material of
Scottish skulls, only met with two brachycephalic crania. Yet
in another way the eventual influence of a persisting metopical
suture upon the shape of the skull may be verified, namely in
32 Lb. ‘BOLK
comparing the average index cephalicus in normal and metopical
skulls. In doing so the following averages were found. That
of the total number of 1400 skulls amounted to 78.3 and that of
the 134 metopical skulls, 78.9. This difference is such an in-
significant one that it does not prove anything as to a sup-
posed more brachycephalic character of metopical skulls. And
the average index cephalicus is such a low one that it by no means
justifies the opinion that brachycephaly is a characteristic of
metopical skulls, or that metopism in general is favorable to the
formation of brachycephalic skulls.
Finally I wish to advance still another proof of the absence
of any relation between the shape of the skuil and the persistence
of a frontal suture. Among the 1400 skulls there were 23 with
the very low index cephalicus of 71, an indication of a very nar-
row skull. And among the 134 metopical skulls, five were found
with the mentioned low index. This fact demonstrates clearly
that metopism occurs even frequently in skulls which are doli-
chocephalic in high degree.
It is well known that for the characterization of a skull its
index cephalicus is a very insufficient indicator, because for
instance the height of two crania with quite the same index can
differ considerably, or the curvatures of the calvarium can be
very dissimilar. And finally this index furnishes not a single
indication as to the absolute dimensions of the skull, a very
large and a very small skull may have an equal index cephalicus.
Hence a comparison of this index in regard to persisting metop-
ical sutures is a very insufficient means of recognizing the ex-
istance of an eventual relation between the shape of the skull
and the frequency of metopism. It is necessary to prosecute
our investigation in still another direction.
_ First we will examine whether the three principal dimensions
of the skull in average are different in normal and metopical
crania. A comparison of the sum of these averages in both
groups of skulls will enable us moreover to answer the question
whether it is true that metopical skulls commonly are larger,
including a heavier brain than nonmetopical crania.
ON METOPISM 33
In the next table the averages are dealt with of the three prin-
cipal dimensions of the 134 metopical skulls and of the total
number of 1400 skulls.
AVERAGE AVERAGE AVERAGE
LENGTH BREADTH HEIGHT
PSeaetGpieal SKUs. ce htcrcss che. ese ke 182 144.8 128.4
VS OGL STILE D8 eas eas ae ee 183.3 143.8 128.6
The height of the skull was measured from the bregmapoint
to the casion.
As is clearly shown by the table, the height of metopical
skulls does not differ from the usual measure, for a decrease of
0.2 mm. is of no consequence. Regarding this dimension it
is certain that there exists no preponderance in metopical skulls.
And also the two other dimensions scarcely testify in favor of
such a supposition. For though it is true that metopical skulls
average 1 mm. broader than normal skulls, their length, on the
contrary, is a somewhat smaller one. The metopical skulls seem
to be shorter and broader than normal skulls. But the differences
are so insignificant that the capacity of metopical skulls equals
that of crania with united frontal bones. And an equality of
capacity includes an equality of brain weight.
Thus it is obvious that neither in the shape, nor in the abso-
lute dimensions is there a striking difference between the two
groups of crania. In this regard the results of my investigation
does not agree with that of some other authors. The metopical
skulls which I examined were not more brachy-cephalic and were
not larger than the normal skulls with which they were compared.
And not without reason I consider the results of my own researches
to be of a greater value than the contradictory results of some
other investigators. For the 134 metopical skulls belonged to
the same group as the non-metopical with which they were com-
pared, the whole collection originating from one source. And
this was not always the case with the material used hitherto by
other investigators.
The result of my research does not harmonize with the already
mentioned views upon the cause of metopism.: I summarize that
THE AMERICAN JOURNAL OF ANATOMY, VOL. 22, NO. 1
34 b.BOuk
a heightened intracranial pressure during growth due to a greater
development of ‘the brain, is considered to be the cause of metop-
ism. Now, I cannot agree with this opinion, for as clearly shown
in the foregoing pages, metopism is independent of the shape
as well as of the size of the skull. And if there really existed
some relation between the degree of development of the brain
and the frequency of metopism, one should expect among the
largest skulls an increased number of metopical specimens and
higher average values of the mean dimensions in metopical
skulls. This is not at all the case. The averages of the three
dimensions in metopical skulls are nearly the same as in the non-
metopical. Therefore a noticeable difference between the ca-
pacity of both groups of skulls cannot be accepted, and con-
sequently the average weight of the brain must be the same.
An objection of more general theoretical nature against the
current opinion about the etiology of metopism may be adduced.
Is it really true that an increase of the intracranial pressure may
prevent the coalescence of two bones of the skulls whose normal
fate is to unite together? Martin, the renowned anthropolo-
gist, accepts this view, founding his opinion upon hydrocephalic
skulls, in which, as he says, metopism is a:common phenomenon.
I do not know how far this statement of the painstaking in-
vestigator is based upon observations by himself, or is merely
the expression of a doctrine propagated in craniological lit-
erature. I am inclined to believe the latter. For the experi-
ence gained by myself upon this matter is in contradiction with
the idea mentioned. There is no concurrence of hydrocephaly
and metopism, hydrocephaly being not at all a condition pro-
pitious for the persistance of the frontal suture. I have examined
carefully the hydrocephalic skulls present in the anatomical
Museum of Amsterdam, and the results of this investigation are
dealt with in the next table. This table informs us of the state
of the frontal suture the horizontal circumference of the skull
and the age. With regard to the circumference it may be
remarked, that in normal Dutch skulls it amounts to 516 mm.
ON METOPISM 30
NO. CIRCUMFERENCE AGE SUTURA FRONTALIS
mm. years
1 684 8 Disappeared
2 673 20 Disappeared
3 616 32 Existing. Sut. sag-
ittalis entirely
closed
4 600 adult Disappeared
5 582 adult Disappeared
6 570 5 Disappeared
By this table it is clearly shown that the assertion that hydro-
cephaly regularly is accompanied by metopism, is a false one.
Only in the third case the suture was still open. But it is a ques-
tion whether in this case the presence of the suture was due to
supposed mechanical influence of the hydrocephaly. For as
mentioned in the table, in this case the sagittal suture was already
entirely closed. And this fact justifies the supposition that in
this case the skull was a metopical one by inheritance, in which
therefore the suture also should have persisted, if the develop-
ment of the brain had been quite normal. But, I admit, this
to be a mere supposition, although I believe that this case may
scarcely be accepted as a proof that metopism is caused by hydro-
cephaly. It seems better to disregard this case in a discussion
of this matter. Furthermore the other data of the table afford
a strong proof against the existence of such a casual relation.
The first two crania are of an extraordinary size, with a circum-
ference met with rarely, even in hydrocephalic skulls. Surely
in both individuals the intracranial pressure must have been an
excessive one. And notwithstanding this circumstance the
frontal sutures vanished without leaving a single trace. And
the same occurred in the other cases mentioned in the table.
I believe the data of this table to be sufficient to justify my
statement, that hydrocephaly by no means produces, as a rule,
metopism. Hence it seems to me an error to pretend that an
increased intracranial pressure—caused by a marked develop-
ment of the brain—is the cause of metopism. For, if the consider-
able increase of this pressure, as surely occurred in the skulls
36 L. BOLK
of the first two individuals of the table, was unable to prevent
the coalescence of the two frontal bones, it is wholly unthink-
able that a somewhat increased development of the brain will
suffice to prevent these bones from uniting.
One may advance still another more weighty question with
regard to the influence of the growing brain upon the skull. It
is assumed that the pressure exercised by the growing brain upon
the inner surface of the skull rises, when the brain is developing
in a greater degree. Is this assumption true? I do not be-
lieve it. It seems to me more probable that with regard to the
expansion due to their growth, the brain and the skull form one
entity, the same hereditary factors determining the growth in-
tensity of the brain as well as of the cranium, I do not believe
that the dilatation of the latter is a mere mechanical phenome-
non, depending on the pressure exercised by its contents. To
some degree this may be the case in pathological circumstances,
as in hydrocephaly or in premature closure of some suture or
other, but under normal circumstances, I believe the intra-
cranial pressure always to be the same, varying only between its
physiological limits.
As a further argument in favor of the assumed influence of
the growing brain upon the expansion of the skull, the fact is
advanced that the forehead in metopical skulls is broader than
in those with normal closure of the frontal suture, this increase
of the transverse frontal measure being another result of the
more strongly developing frontal lobes of the brain. Without
doubt, the observation made f. 1. by Welcker and Papillante is
right, and I am able to confirm the same, the metopical skulls
of my collection having an average breadth of the forehead of
99.7 mm. and the nonmetopical one of 96.5 mm. But I cannot
agree with the interpretation of the phenomenon given by the
above mentioned authors. I think in this matter they are con-
fusing cause and effect. The difference may be elucidated in
the following way. If the frontal suture does not disappear
during the second year, the apposition of bony tissue in it is con-
tinued during a longer space of time than in case of its disappear-
ance in the normal way, and therefore there is a very favorable
ON METOPISM 37
opportunity for the forehead to grow broader than usual. It
seems therefore quite reasonable that in metopical skulls the
forehead is broader, this being the natural consequence of the
fact that the growth-centrum remains longer in an active state.
With regard to the problem of metopism, observations as
well as theoretical considerations have convinced me, that the
common opinion about the aetiology of this phenomenon is an
erroneous one. As to the facts, I have been unable to confirm
the existence of any relation between metopism and a particu-
cular shape of the skull, the frontal suture persisting in dolicho-
cephalic crania as frequently as in brachycephalic ones, and the
index cephalicus being in average equal in metopical and non-
metopical skulls. Furthermore, the metopical crania of my
collection were not larger than the normal specimens, consequent-
ly the average of the brain-weight should be equal in both groups.
There is but one fact which I was able to confirm, namely the
greater breadth of the forehead in metopical skulls, a phenome-
non easily understood as a logical consequence of the protracted
activity of the frontal suture.
And as to the theoretical side of the problem, I do not agree
with the current opinion that metopism is caused by an increased
intracranial pressure, the result of a greater development of the
brain. First, because the least indication of such an increased
development is wanting, and secondly because in pathological
cases, as in hydrocephaly, in which undoubtedly the intracra-
nial pressure had considerably risen, the frontal suture disap-
pears as in normal circumstances.
Before entering into an explanation of my views upon the
aetiology of metopism, I wish to discuss briefly the argument
that metopism is less frequent in the lower races. As mentioned
in the introduction to this paper, this fact is utilized as a proof
that metopism, caused by a larger expansion of the brain, should
be a symptom of higher intelligence. I think this opinion can-
not withstand a serious analysis. If one accepts the principle
that metopism is a symptom of intellectual superiority as true,
because it is more frequent in culture races, than in uncivilized
ones, one must accept also the consequence of this principle, that
38 tT. BOLE
amongst the culture nations those are psychically the most fa-
vored in which metopism is the most frequent. Now in the mid-
dle region of the continent and in Russia metopism occurs in
about 6.5 per cent, according to Schwalbe, Ranke, Gruber and
others. Inthe northern part of Europe, the phenomenon is more
frequent, and attains 9.5 per cent according to Bryce, Simon
and myself. In Frisians, occupying the northern region of the
Netherlands, metopism amounts even to 11.4 per cent. Though
the acceptance of the principle should be very flattering for the
Dutch people, I do not accept its exactness, metopism having
nothing to do with intelligence. I think the interpretation of
the different frequency of metopism in the inhabitants of the
central and the northern region of the continent to be this: that
it is simply a racial difference, the phenomenon occurring more
frequently in the Homo nordicus than in the Homo alpinus.
-The opinion that the difference in frequency of metopism in
the human race is a mere physical anthropological character
also holds good with regard to a comparison of civilized and un-
civilized races. In the former, metopism is commonly very
rare. What may be the reason of it? The authors, who hold
that the metopism is the result of an increased intracranial
pressure, caused by a somewhat hypernormal growth of the
brain, adduce this difference as a proof of the exactness of their
doctrine, obviously supposing that such a hypernormal growth
does not occur in uncivilized races. In this argument there is
a very obvious mistake. Surely the average weight of the brain
is a lower one in uncivilized races. But the individual weight
of the brain differs in uncivilized races as well as in culture
races. Not only among white men, but also among Negroes
and Papuans there are individuals with sub-normal, normal and
hypernormal volume of their brain. And if really a strongly de-
veloped brain should cause an increased pressure upon the.inner
surface of the skull, this condition is realized as well in a Papuan
with a hypernormal development of his brain, as in an European.
Nevertheless in Papuans and Negroes, metopism is rare. I con-
sider this a further proof that the persistence of the frontal suture
ON METOPISM 39
has nothing to do either with brain development, or with the
higher or lower degree of intellectual evolution.
Now I wish to express my opinion upon the aetiology of meto-
pism. In the introduction to this paper a brief account is given
of the phylogenetic history of the frontal suture, principally in
Primates. I summarize that among the Prosimiae in some fam-
ilies the frontal suture, as a rule, persists, while in others, on the
contrary, it disappears. In monkeys both frontal bones unite
together at a very early stage of development, but in some in-
dividuals the suture may persist. In Anthropoids till now the
suture has never been seen in an adult specimen. This summary
shows that in the course of the phylogenetic evolution of man,
originally both frontal bones remained separated; thereupon in
the higher degree of evolution the bones coalesced, and finally
in man the primitive state presents itself again in a number of
individuals. These facts form the basis for a conception of the
aetiology of metopism differing from those previously advanced.
For it seems to me necessary to begin by discovering the cause
which caused the suture to disappear in monkeys. Having elu-
cidated this point, we have approached more closely to the solu-
tion of the metopical‘problem in man. For the possibility must
be taken into consideration that the influences which were acting
on lower Primates and caused the concrescence of the two fron-
tal bones, have lost their significance and activity in man. If
this really happened, it is quite comprehensible that the frontal
suture reappears. For in each individual both frontal bones
arise separately, the bilateral condition being the rule in the
younger stages of development even in such forms in which the
individual is born with an already ‘single frontal bone. The
metopical suture in an adult individual hence represents no new
condition, no alteration of a primitive state, but simply the con-
tinuation of an original condition. There must be a special
cause for a union of the bones whereas there is no new fac-
tor required for the explanation of the fact that they may remain
separated. Let us therefore try to find out the primary cause
of the concrescence of the frontal bones in monkeys, afterwards
we can examine whether this cause became inactive in man or
not.
40 L. BOLK
It is a well established fact that the shape of a bone and es-
pecially its internal structure, are the results of the mechanical
and muscular forces acting upon it. In accordance with the
mechanical principle of securing the maximum of strength with the
minimum of material, the cancellous tissues of each bone is
so arranged as best to withstand the strains and stresses to which
the bone is usually subjected. So the internal architecture of
each bone is quite in accordance with the fundamental laws of
physics; systems of ‘pressure lamellae’ running in definite direc-
tion are crossed by sets of ‘tension lamellae.’ A great number
of investigators have tried with good results to analyze the struc-
ture of the different bones of the human skeleton from this point
of view. Only in regard to the skull in general, and particularly
the cranial vault, are we without definite knowledge as to the
structure of the bony framework of the different bones of the
skull and the relation between the statical and dynamical
external forces to which it is subjected. The whole of our knowl-
edge is confined to the fact that the structure of the plate-like
bones of the cranial vault exhibits the following appearance: the
outer and inner surfaces are formed by two compact layers,
having sandwiched between them a layer of cancellous tissue.
Nevertheless concerning the cranial vault we find ourselves
under relatively favorable circumstances, because the general
conditions are so very simple here that the problem can be
elucidated sufficiently from a mere theoretical standpoint. For
the function of the cranial vault being principally a protective
one, the number of mechanical stresses to which the frontal
half of the skull is subjected is slight. There are but two factors
to take in consideration, namely the weight of the facial cran-
ium with the soft parts of the face as a constant working
factor, and the pressure effectuated by the temporal muscle
during its contraction. The weight of the facial cranium is
transferred surely for the greatest part by means of the zygo-
matic arches to the middle of the base of the cranium, and so
there remains as the only important external force acting upon
the anterior and lateral part of the skull, the pressure of the
temporal muscles, when the jaws are firmly closed. Surely this
ON METOPISM 4]
stress will determine the arrangement of the cancellous tissue
in the frontal bone. And the variations in the arrangement and
the course of the pressure and tension lamellae in different ani-
mals, without doubt is caused by the variable relation between
the frontal bone and the Musculus temporalis. If the muscle
arises largely from the frontal bone the internal structure of the
anterior region of the cranial vault will be largely influenced
by the same. It is obvious that in such a case the frontal and
sagittal suture are primarily subject to this influence, as their
course is perpendicular to that of the fibers of the muscle.
I think this idea is sufficient to demonstrate why in lower Pri-
mates the frontal suture persists, while in the higher Primates it
regularly disappears. For the stress of the masticatory muscles
tends to compress the skull in a transverse direction and the vault
of the skull will withstand this force by a system of trajectories,
running on a frontal plane. Now it is not difficult to understand ©
that it is of advantage that the trajectories do not meet with an
open suture in their course. And so the fate of the metopical
suture in Primates will depend upon the topographical relation
between the temporal muscle and the frontal bone. If the muscle
arises from the frontal bones a system of pressure and tension
lamallae will be developed in it crossing the median line and hence
necessitating the union of the two primary frontal bones. If
on the contrary, the bone remains free from the dynamical in-
fluence of the muscle, there is no reason for the union of the two
bones.
In figure 1 an attempt is made to elucidate the above described
idea by means of a very simple scheme. It represents a frontal
section of the anterior part of the vault of the skull, with the
temporal muscle on both sides. The direction in which the
vault will be narrowed by the stress of the contracting muscle
is indicated by two arrows. It is obvious that in order to with-
stand this stress pressure trajectories will be developed in the
vertical parts of the vault, under the direct influence of this
force. The compression in the indicated direction will produce
a tension in the top of the vault. And while in the vertical
parts of it the cancellous tissue will arrange itself in pressure
42 Li BOLE
lamellae, on the top a system of tension lamellae will arise. In
the figure both systems are represented by some simple lines. I
‘admit it is a purely theoretical construction, which I have tried,
however, to bring in accordance with the principles of mechanics.
The point upon which I will lay some stress, is that the tension
lamellae necessarily must cross the median plane. And because
an interruption in their course by a suture would be contrary to
their mechanical function, the two frontal bones unite together.
Now we will examine in how far the anatomical conditions in the
different Primates agree with the principles worked out above.
It is needless to give a long description of the anatomical
conditions in several specimens,: for the inspection of some few
crania suggests the regularity in the special groups of the Pri-
mates. I will confine myself therefore to treat each group as
a whole.
The examination of the prosimian skull shows that in this
lowest group of Primates the frontal suture is a constant element
in the system of sutures, disappearing nearly at the same time
as the other sutures. I regret to have at my disposal only a
small number of skulls of prosimiae. Hence it is impossible
for me to give a summary of the age at which the metopical
suture disappears in the different genera of this group of Primates.
The small number of skulls in my possession indicate that a
considerable variability exists as to this point in the different
genera of the Prosimiae. So I found among five adult skulls of
Lemur only one specimen with the system of sutures still wholly
ON METOPISM 43
intact, including the metopical suture. In the others the system
had completely disappeared. In three adult crania of Avahis
on the contrary, apparently of old individuals, all sutures includ-
ing the metopical, were still present, and so it was in two old
erania of Nycticebus. It thus seems that the sutures in Pro-
simiae close at a very different stage in the different genera of
this family. But for the present it suffices to know that the
disappearance of the metopical suture takes place simultaneously
with that of the other elements of the system. There is no spe-
cial factor necessitating the same to close at an earlier period
than the other sutures. In this respect the Prosimiae differ from
the monkeys and apes in which the closure of the frontal suture
always precedes those of the other sutures, and often very con-
siderably. From this we may conclude that the influence compel-
ling the metopical suture in monkeys and apes to disappear, is
absent in Prosimiae. Now a comparison of the topographical
relations between the temporal muscle and the frontal bone in
the lower and higher Primates, reveals that in Prosimiae the
muscle does not arise from the frontal bone at all. The reason .
for this is obvious. In Prosimiae the lateral wall of the orbit
is a very incomplete one, and frequently also the floor of this
fossa is restricted to a foremost part. As a rule the outer wall
only is represented by an arch extending from the facial root of
the zygomatic arch to the parietal margin of the frontal bone.
This insertion of the orbital arch at the hindermost border of the
frontal bone causes the latter to be situated completely in front of
the temporal fossa, hence the temporal muscle cannot extend
its origin forward upon the frontal bone. In monkeys, as in
apes and man, the outer wall of the orbit is a complete one,
formed partly by the orbital surfaces of the zygomatic bone
and the great wing of the sphenoid bone. By this outer wall
the orbit is separated almost completely from the temporal fossa
and the plane of entrance of the orbit is considerably turned.
In Prosimiae the inclination of the latter is more a lateral than a
frontal one, the axis of the orbit making a more open angle with
the median plane. But in monkeys the plane of entrance is
turned, being directed principally forward and but slightly out-
44 L. BOLK
ward. The axis of the orbital fossa is making therefore a more
acute angle with the median plane. In consequence of the ro-
tation of the plane of entrance of the orbit, the insertion of the
primitive orbital arch at the frontal bone was shifted from the
hindermost border of the bone forward, so that a part of the outer
surface of the frontal bone is added to the temporal fossa. By
this enlargement of the fossa the temporal muscle was enabled
to arise to a smaller or greater extent from the frontal bone.
The differences between Prosimiae and the higher Primates
are clearly shown by the figures 2 to 9. In these figures the lat-
eral and superior view of some prosimian and simian skulls
is drawn. ‘The course of the main sutures and also the extension
of the temporal muscle is indicated. Figures 2 and 3 represent
lateral views of the cranium of Avahis sinavensis and of Stenops
gracilis respectively. In both it is obvious that the frontal bone
is completely excluded from the temporal fossa, and that there
are no fibers of the temporal muscle arising from this bone.
Hence it is easy to understand that in those crania the frontal
suture persists, as is shown in figure 4, representing the superior
view of the skull of an Avahis niger. The frontal bone remains
free from the dynamical influence of the temporal muscle, its
anatomical significance is a restricted one. It functions only
as roof of the orbits and the foremost narrow part of the cavity
of the skull. In consequence of the absence of forces acting
upon this bone, its system of trajectories cannot be strongly de-
veloped. Hence there is no reason for both frontal bones to
unite.
Quite the contrary happens in the skulls of monkeys from the
Old and New World, as is illustrated by figures 5, 6, 7, and 8.
Figure 5 represents a side view and figure 6 a superior view of
the skull of Chrysothrix, a platyrrhinic monkey, figure 7 a side
v ew of the skull of Macacus, and figure 8 such a one of a female
Gorilla. The extension of the temporal muscle and the course
of the sutures in the cranial vault are drawn. ‘These figures
require but little comment. In all it is clear that the frontal bone
participates in the formation of the temporal fossa, and that no
small part of the temporal muscle takes origin from this bone.
ON METOPISM 45
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, : le.
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46 L. BOLK
In Maeacus and Gorilla the origin of the muscle reaches to the
median line, so that there is but a small triangular part of the
outer surface of the bone uncovered by the muscle, while in
Chrysothrix a narrow strip on both sides of the median line re-
mains free from the origin of the muscle. It requires no special
argument to show that the forces executed by the contracting
muscle upon the frontal bone must give rise to a system of tra-
jectories in it, able to withstand the strains on its outer surface.
And it is important to draw attention to the fact that, the fibers
of the muscle are directed perpendicularly to the median line and
consequently also with regard to the frontal suture, the forehead
being directed horizontally immediately behind the superciliary
arch. This condition surely favors the formation of trajecto-
ries crossing the median line and causing the frontal suture to
disappear, as really occurs in all monkeys and apes. In man
the condition is greatly changed, though a small part of the
frontal bone is still participating in the formation of the tempo-
ral fossa, as shown in figure 9. There are two circumstances by
which the relation between the temporal muscle and the frontal
bone became altered from that obtaining inmonkeys. Firstly, the
frontal bone in man is much larger, and the surface of it occupied
_ by the origin of the temporal muscle is considerably smaller in
man than in apes. The pressure of the muscle upon the outer
face of this bone in man cannot be a very strong one, hence its
influence upon the inner structure surely is of little importance.
In this respect the condition in man is getting closer to that in
Prosimiae.
The second circumstance peculiar to man is the well-pro-
nounced curve of his frontal bone. By this curve the greater
part of this bone rises vertically above the orbits. In apes, as
pointed out, the fibers of the temporal muscle are directed per-
pendicularly to the whole length of the fronta' suture. In man
th's condition is altered, for in consequence of his strongly curved
forehead the greater part of the frontal suture is situated in front
of the anterior border of the temporal muscle, and moreover is
directed nearly parallel to this border.
ON METOPISM 47
By these two circumstances the frontal suture in man becomes
independent from the dynamical influence of the temporal muscle.
Hence in man there is a return to the conditions as met with in
Prosimians, though the anatomy of the skull and the muscles is
quite different. The mechanical cause for the disappearance of
the suture in monkeys having fallen out, the circumstances be-
come very favorable to the persistence. Now it is obvious
that these conditions act most favorably in individuals with a
more prominent forehead and a less pronounced development of
the masticatory musculature. In the white race therefore, the
possibility for the persistance of the suture is far greater than in
the races with a more flattened forehead, a higher development
of the dentition and of the temporal muscle. And this may be
considered the cause, accounting for the fact that commonly
metopism is more frequent in Europeans than in Negroes or
Australians.
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ON THE FREQUENCY OF LOCALIZED ANOMALIES IN
HUMAN EMBRYOS AND INFANTS AT BIRTH
FRANKLIN P. MALL
EIGHTEEN FIGURES
In a paper published nine years ago on the causes underlying
the origin of human monsters, I made the assertion that Jocal-
ized anomalies were more common in embryos obtained from
abortions than in the full term fetus, without, however, adduc-
ing conclusive evidence in support of this theory.t
In a footnote on page 27 of that publication I gave a list of
embryos with their chief defects, comparing them with the
percentage of frequency of monsters born at full term. An
objection to be raised to such a statement is the fact that there
is not a complete correspondence between anomalies in the
embryo and those found in the fetus at the end of pregnancy.
For instance, spina bifida in young embryos is always complete
while at full term the open canal is covered over with skin.
Cyclopia and exomphaly are the same in the embryo as at
birth, but the deformities of the head and neck of the embryo
are of such a nature that it cannot live long enough to admit
of comparison with lke malformations found at term. With
these difficulties clearly before me, I have made an effort to
define sharply the anomalies in embryos, so that a satisfactory
comparison might be made with those found in monsters at the
end of pregnancy, as described in the literature.
I shall mention first cyclopia, for it seems to me that it is
the type of monster which is now best understood. This clearer
conception is due largely to the excellent experimental work of
Stockard, and partly to the fact that the eyclopean state can
exist quite independently of other marked deformities of the
1 Mall, F. P. A study of the causes underlying the origin of human monsters.
Jour. Morph., vol. 19, 1908.
49
THE AMERICAN JOURNAL OF ANATOMY, VOL. 22, No. 1
50 FRANKLIN P. MALL
embryos. I have previously discussed the question of cyclopia
in a separate publication, and it is not therefore necessary for
me to dilate further upon it at present.2- Hare lip is also sharply
defined in the embryo and is as readily recognized as exomphaly.
Other anomalies, however, are more difficult to recognize as
sharply defined malformations in the embryo.
We have in our collection about 2000 embryos. The patho-
logical specimens of the first 400 were reported in my paper on
the origin of human monsters mentioned above. Since the
collection was taken over by the Carnegie Institution of Wash-
ington, it has grown at a very rapid rate, about 400 specimens
being added to it each year. I have in preparation a more ex-
tensive study of pathological embryos, and during the past year
have practically completed a careful study of the first thousand.
While this was in progress, another thousand specimens were
added to the collection. At present, however, only the first
thousand will be considered, the remainder not having been
sufficiently tabulated to be of statistical value.
We have introduced and are gradually perfecting a system
of classification of the embryos which will enable us to locate
any specimen in our collection and the record thereof by means
of a card catalogue. Reasons for adopting this system were
given in a circular recently published. The specimens can
clearly be divided into two groups according to their origin,
i.e., uterine and ectopic. In both of these, the embryos which
are normal in form are catalogued according to their sitting
height, which we call crown-rump (CR). All embryos there-
fore which are apparently normal, say 10 mm. long, are entered
upon one card. What happens to these specimens subsequently,
whether they are dissected, sectioned or preserved permanently
as whole specimens, may also be entered upon this card without
interference with the system of classification. The chief dif-
ficulty is to determine what constitutes a normal embryo, and
> Mall, F. P. Cyclopia in the human embryo. Contributions to Embry-
ology, vol. 6, Publication No. 226, Carnegie Institution of Washington, 1917.
’ Mall, F. P. Embryological collection of the Carnegie Institution, Circular
No. 18, 1916.
LOCALIZED ANOMALIES IN HUMAN EMBRYOS 5 ll
here we must rely largely upon our experience in human and in
comparative embryology. A sharply defined, well formed white
embryo, with blood vessels shining through its transparent
tissues, is considered normal. If it is partly stunted and opaque
or disintegrating, it is considered pathological. A further study
of the normal embryo, however, shows that in many of these
specimens the membranes are decidedly pathological. For
instance, the villi may be deformed, diseased, atrophic or hyper-
trophic, or the contents of the amnion and the exocoelom may
be unusual. Nevertheless, in all of these cases we still classify
the embryos as normal, although fully cognizant of the fact
that the surrounding membranes are pathological; otherwise it
would be difficult to account for the great number of spon-
taneous abortions. The theory is that the embryo was devel-
oped under pathological conditions, but that the chorion was
not sufficiently affected to cause any apparent change in the
embryo. If an embryo included in this group is apparently
normal in all respects save one, we still consider it normal with
a localized anomaly. In fact we are gradually forced into this
position, as an embryo, considered at first to be normal, may
later on prove to have a localized anomaly, such as spina bifida
or cyclopia. As far as we can determine, such an embryo would
have been able to survive longer had not something happened
to its membranes, thus causing its expulsion. I am inclined to
believe that pregnancies of this sort, if carried to term, would
produce the ordinary monsters described by teratologists. As
the study of our collection of specimens is continued by different
members of the staff, localized anomalies, when found, are
recorded in our card catalogue, without, as stated above, neces-
sitating any rearrangement. When these anomalies are present
in normal embryos, the embryos are classed as normal, with
localized anomalies.
The second group of specimens, which are termed patho-
logical, are in a way more interesting, and their study justifies
our method of classifying localized anomalies with normal
embryos. We have in this group a variety of changes ranging
from those found in fetus compressus down to complete disin-
52 FRANKLIN P. MALL
tegration of the ovum, leaving only a few villi. Having made
numerous efforts to classify these specimens, I have finally
resolved them into seven groups which I shall consider in their
reverse numerical order.
The seventh group, shown in figure 7, is composed mostly of
larger specimens which are either dried up and deformed, or
macerated and soft. These, of course, apparently merge into
each other, and for this reason we have had to consider them as
a single group. We hope, however, in the course of time to be
able to subdivide them, for it is well known that fetus compres-
sus 1s extremely rare in pigs and other lower animals, while
edematous and macerated embryos are quite common. It
appears that the type of fetus in this group develops as a normal
embryo during the first portion of pregnancy, and then dies
slowly, either undergoing maceration, or being transformed into
a fetus compressus. In the latter the cord is long, thin and
greatly twisted The structures of the embryo show that there
has been a slow tissue growth which has not been sufficiently
rapid to allow the normal development of the extremities. In-
stead the hands and feet are club-shaped, and in several in-
stances there are adhesions beween the extremities and the
body We also find very pronounced and quite characteristic
changes in the placenta of the fetus compressus, there being
beween the villi lage masses of chromatin substance presenting
much the same picture as the photograph of a comet, a central
nucleus with scattered granules extending from it. Generally
in our notes we speak of this substance as nuclear dust.
The sixth group of specimens we term stunted (fig. 6). The
form of the embryo is easily recognized, but the head is atrophic
as are also usually the extremities. At the time of the abortion
the tissues are quite transparent, giving every appearance of
a living embryo, but with increasing knowledge concerning
tissue cultures and growing isolated cells, we can see in speci-
mens of this sort an active but circumscribed tissue culture of
a clump of differentiated tissues. In other words we have a
tissue culture of the entire embryo, which on account of faulty
or arrested circulation, grows in an irregular manner. Changes
LOCALIZED ANOMALIES IN HUMAN EMBRYOS 53
of this sort in an embryo I have designated in my paper on
monsters as a dissociation of the tissues. I picture to myself
something like the following sequence: when the ovum comes
into the uterus which is more or less diseased, it becomes some-
what poisoned and consequently does not implant itself well.
This naturally results in an irregular growth of the chorionic
villi; in turn the embryo is affected and it is only natural to
infer that the most direct influence would be through the vascu-
lar system, soon ending in poisoning of the heart and frequently
in the interruption of the circulation. In such specimens the
nutrition would reach the embryo through the exocoelom. In
fact one of the earliest indications of a pathological specimen is
an increased amount of magma in the exocoelom. Embryos,
which are thus cut off from the chorion, continue to grow in an
irregular manner; the tissues are more or less dissociated, and
the specimen as a whole is stunted. Hence the designation.
In the fifth group (fig. 5), the process of stunting has pro-
gressed to such an extent that the extremities are almost
entirely lacking and only the head end can be recognized with cer-
tainty. On account of their shape, due to this extreme stunting,
we speak of these specimens as cylindrical embryos. Falling
frequently into this group are embryonic remnants which,
however, really do not belong there, since a primary examina-
tion with a binocular microscope does not permit of a sharp
differentiation between this and other cylindrical forms of
stunted embryos. Close examination with a microscope reveals
specimens of this sub-group to be composed of a naked um-
bilical cord belonging to an older embryo which had disinte-
grated, or as seen in a few instances the embryo has been torn
off by mechanical means during abortion. As rapidly as the
sub-type is recognized, it is labeled in the card catalogue in
parenthesis (cord) so that in studying these specimens we may
distinguish between the naked cords and the true cylindrical
forms of pathological embryos.
When the process of dissociation of the embryo begins in
still earlier stages than those belonging to the older groups (Nos.
5, 6, and 7), the result is a nodular body representing the embryo,
54 FRANLKIN P. MALL
but the change in it is so complete that it is difficult to recognize
the different parts of the embryo except in a general way (fig. 4).
The coelom, heart and central nervous system can readily be
made out. Sometimes there are pigmented spots in one or two
of the sections, marking the position of the eyes. This group
again divides into two quite sharply circumscribed sub-groups:
first, those with an umbilical cord to which the dissociated
embryo is attached together with the umbilical vesicle; and
second, a vesicular group composed of specimens in which there
is only the remnant of the umbilical vesicle, the embryo being
nearly or entirely destroyed. Had it been possible in every
instance to differentiate between these two types of specimens
in the primary examination, they would, of course, have been
recorded as separate groups; but this could not be done without
sections and a microscopic examination. Therefore, for the
present we must consider them together. In our ordinary
laboratory parlance we speak of them as the nodular group.
In the third group, both embryo and umbilical vesicle are
completely destroyed, but we can see within the degenerated
chorionic sac a more or less complete amnion. ‘This group is
designated as the one in which the specimens are composed only
of the chorion and the amnion (fig. 3).
In the second group the amnion is destroyed and there re-
mains only the chorionic vesicle containing the coelom. This
is usually filled with reticular magma and scattered cells, which
may represent all that is left of the embryo (fig. 2).
Finally in the first group the form of the ovum is destroyed
and the specimen consists only of the vill which have under-
gone fibrous or mucoid degeneration. Sometimes only a few
of the villi are found, at other times there is a large cluster cling-
ing to a single stem, and some specimens are composed of large
masses of villi which form malignant hydatidiform moles. Such
a mass may weigh a kilogram (fig. 1).
It can be readily seen that the above classification into sub-
groups is arranged somewhat in the order of the age of the ovum
when it began to degenerate. Generally these changes are so
pronounced that the embryo cannot live through the duration
of pregnancy and this accounts for the abortion.
Wt
LOCALIZED ANOMALIES IN HUMAN EMBRYOS or
As far as localized anomalies are concerned, we naturall do
not find them in the first four groups, while in the remaining
three groups we encounter only such as are very pronounced
and stand out clearly in spite of other changes in the embryo.
Fig. 1 Illustrating Group 1, composed exclusively of villi. Specimen No.
749 received from Dr. G. C. McCormick, Sparrows Point, Md. X 2. These
hypertrophic villi came from a hydatiditorm mole weighing over a kilogrsm.
Fig. 2. Illustrating Group 2, chorion with coelom. No. 1289 from Dr. J. R.
Cottell, Louisville, Ky. 2. The picture shows the coelom filled mostly with
granular magma.
Fig. 3 Illustrating Group 3, chorion with amnion. No. 813 from Dr. H. D.
Taylor, Baltimore. X 3. The cavity of the ovum is filled with a dense mass
of granular magma.
rp
510) FRANKLIN P. MALL
Thus, for instance, with fetus compressus we frequently recog-
nize club-foot; in stunted forms, hare lip and spina bifida, and
in cylindrical forms, spina bifida. Of course, if eyeclopia is
encountered in any of these forms, it is looked upon as a loeal-
ized anomaly in a pathological embryo. On the other hand, a
single anomaly in an embryo called normal can easily be recog-
fig. 4 Specimen illustrating Group 4. The ovum contains a nodular embryo;
No. 1140b from Dr. George T. Tayler, Greenville, S.C. X 15.
Fig. 5 Illustrating Group 5. Ovum containing a cylindrical embryo; No.
839 from Dr. W. S. Miller, Madison, Wis. X 14.
nized, and it is from this group that we should expect
the development of monsters had the pregnancy progressed to
term.
A few illustrations of localized anomalies are given in the
figures in order to show that they are identical with those found
in infants at birth. Figures 8 and 9 are specimens of cyclopia
and double monsters in normal embryos. Figure 10a and
(ed) |
—
LOCALIZED ANOMALIES IN HUMAN EMBRYOS
10 b show an embryo and a fetus with hare lip. Figure 11, 12
and 13 have pronounced localized anomalies and need no further
explanation. Finally figures 14 to 18 show anomalies of the
hand the first and last are of the hereditary variety, and figures
15 and 16 show acquired anomalies, that is, they were subse-
quently formed in an embryo which started its development
normally. It is proper to remark here that these illustrations
are mostly from specimens from the second thousand of our
6c
Fig. 6 Group 6. Three stunted embryos to illustrate this group. 6a, No.
1295d from Dr. B. T. Terry, Brooklyn, N.Y. X4. 6b, No. 1523 from Dr. G. B.
Ward, Gilman, Iowa. X 2. 6c, No. 1477 from Dr. H. B. Titlow, Baltimore.
S< Gk
collection but this is for the reason that recently we have made
many more photographs and secondly, many of the specimens
in the first thousand have already been figured in my paper on
monsters.
In order to render possible a comparison between localized
anomalies found in pathological and those found in normal em-
bryos, the following six tables have been constructed. Table
58 FRANKLIN P. MALL
1 gives the classified distribution of the first 1000 embryos in
the Carnegie Collection. The primary division comprises two
classes—pathological and normal. The pathological in turn is
arranged in the seven groups just described. The normal are
arranged in groups to correspond as nearly as possible with the
7b
Fig. 7 Group 7, giving two specimens of fetus compressus. 7a, No. 996
from Dr. H. B. Titlow, Baltimore, * 2 7b, No. 868 from Dr. E. H. Egbert, Wash-
ington >< 2:
ages of the embryos in lunar months. In order to define clearly
which embryos belong to a given month, I have inserted their
probable lengths for each month in table 6. Thus, for instance,
the second month includes all specimens from 2.6 mm. to 25
mm. in length, ete. (Data upon the estimated age of embryos
LOCALIZED ANOMALIES IN HUMAN EMBRYOS 59
may be found in my chapter on the age of embryos, contained
in the Manual of Human Embryology.)!
It will be noted in these tables that the specimens are
arranged in centuries; that is, each line in the table includes
exactly 100 specimens. The first century includes specimens
Nos. 1 to 98, the second, Nos. 99 to 205, and so on. This ad-
justment was necessary for the reason that frequently a single
number is given to two or more specimens. Sometimes the
| Ss
L = Y
Fig. 8 Normal embryo with cyclopia; in front of the eye is seen the cyclo-
pean snout. No. 559 from Dr. B. J. Merrill, Stillwater, Minn. X 5.
Fig. 9 Normal double monster. No. 249 from Prof. L. Hektoen, Chicago.
Natural size.
first is called a and the second, 6; or the first may be given the
number, and the second the letter a, ete. The second century
passing from Nos. 99 to 205 includes more than 100 numbers,
because specimens which are given a number are frequently
found upon further examination not to contain any remnants
of the ovum, and for this reason they are to be discarded. In
our catalogue they are later marked as ‘no pregnancy.’ Finally
the full 1000 ends with embryo No. 900g. The individual
entries are percentage records. Thus in the fifth century, there
4 Determination of the age of human embryos and fetuses. Human Em-
bryology, Keibel and Mall, vol. 1, Chap. 8. 1910.
60 FRANKLIN P. MALL
Fig. 10 Two specimens of hare lip. 10a, No. 364 from Dr. B. J. Merrill,
Stillwater, Minn. X 3. There is also exencephaly in this specimen. 10b,
No. 982 from Dr. G. C. McCormick, Sparrows Point, Md. X 2.
Fig. 11 Stunted fetus with a large hernia in umbilical cord, also spina bifida.
No. 1330 from Dr. A. R. Mackenzie, Capitol Heights, Md. X 1}.
Fig. 12 Normal embryo with exencephaly and spina bifida (the latter op-
posite the arrow). No. 1315 from Dr. J. C. Bloodgood, Baltimore, X 2.
Fig. 13 Normal fetus with hernia of midbrain. No. 1690 from Dr. P. F.
Williams, Philadelphia. X 9.10.
LOCALIZED ANOMALIES IN HUMAN EMBRYOS 61
are 41 normal specimens of the second month; that is, of this
hundred, 41 per cent of the specimens are normal embryos of
the second month, whereas the total for the full 1000 has been
brought down this percentage to 24.5.
IE)
Fig. 14 Anomaly of the left hand in which only the thumb and little finger
are normal. No. 306a from Dr. F. A. Conradi, Baltimore. x 3.
Fig. 15 Left hand which is club-shaped from a fetus compressus. No. 230,
CR 57 mm., from the late Dr. J. P. West, Bellaire, Ohio. Natural size.
Fig. 16 Deformed wrist with atrophic radius in a normal embryo. No.
789, CR 50 mm., from Dr. H. F. Cassidy, Roland Park, Md. X 2. The same
kind of wrist is seen in the specimen illustrated as figure 11.
Fig. 17 Right hand with six fingers from macerated specimen. No. 1749
from Dr. 8S. M. Wagaman, Hagerstown, Md. X 2. This specimen had six digits
on all four extremities.
Fig. 18 Double little finger of the left hand of the same specimen. X 2.
62
FRANKLIN P. MALL
TABLE 1
Giving the distribution of 1000 specimens
ow PATHOLOGICAL, IN GROUPS NORMAL, IN MONTHS
= CATALOGUE
p NUMBER =
z Le) 3 | 5 6 7 = 1 2 3 4 5 6 7 8 9 | 10
8 a
1 1— 98 | 1) 5) 1 6) 4 3 aa ais Wh IEPA BS A Oe) OF Oh |) @
2 99-205 Oy) CH Te SRS Ge Males 9) (0s |) SO) By Pall 7 2 BO @: | Oo)
3| 206-295 PANE OY Vedi) ube | Ze |) esa aL {| PAB asa 7 ok ak CO |} 0) I] -@) |) a
4) 296-380 ZA EE eG) 7) ay aL a TE) 2 PO). | ©. |} il
Bl) SAS || ay AS 70 |) | |) a2) ate) GEO I a Oe Oey @ | ©. PG
6| 477-571 MNO ee oth |) SU) OPA AG) 4 Ney Ih Oat a) |G
7 SPSS | SANG a || Gy 4) fy |] Ss I) B33) ) ey all) ss ess PO) O | ©
8| 652d-729 AM Tale yell |) ae || |) YE ah USP USO) ze a IE |) © 4) 1
DAS SSL fool) Sl LS |e lan oye |i Z| ee ele eA | 2S SS DCO CO
10} 817-900g | 9} 8|}0| 47) 4 Gel SSialay 14s Qhhe7 (8.41'6)| “21 08) Ores
36/71/21 |51 |75 |80 |62 |396|11 |245)180/93 |41 |18 | 8 | 2| 0/6
In determining the normality of specimers, the criterion used
was the shape of the embryo, judging this as best we could by
our own knowledge of human and comparative embryology, as
well as by the experience of other students of human embryology,
and we have used freely the atlases of His, Hichstetter and
Keibel and Else in making our decisions on this point. How-
TABLE 2
Specimens obtained from the uterus
£
aie A ELS) & | 4 SARC T at 2s ioe eo] 5 Grol ele Seal acces ene
4 : 5
3 é i
1 1— 98 IW ea TBC eeeS ies | 28 |) el By] ZU ale tes [oe OO) PO) |] @ |) Fe
2 99-205 OS) L | 8 6 2 6A ON F221 520 N64) 2) | 25205 Os ROR POR a2
3} 206-295 25) O38 | OL TAT te eee ea ee) Or Os O eaten mata
4) 296-380 HES OV 3 | SSW Ge SG lal eG ee A eS ze Oi OM ile irs
5| 381-476 WA 313 | 7 | 9 See Se) Sale Sia le 2c OO 0 sO a eOs ier
6| 477-571 NO el eee WG | Se OO) jp st Me ay EO 2 ©) @ | as
“|. 5¢2=652e | 1) 4)4.| 3) 5 | 5 | 8) 80) 0.24) 21/10 | 35) 2°) 3))°0) |, 0; OaiiGs
8} 652d-729 WEB ee AMON eyes fea) Tk lsh) TUNG) ae ay |) WE Oe] CO) fp ak |) full
9| 730-816b | 2] 5) 1 | 5] 6 | 4 10 | 33) 1 Sie a aed ole COM ON: Ol ON meta
10} - 817-900g 2). 4) 0.) 3.) 5 | 2) 5 | 20) 2 td W897) 83).6°) 2 | 0 | Oi Saisas
12|/39|18 |48 167 |74 |55 |313/11 |213/170/91 |41 |18 | 8 | 2 | 0 | 6 |560
LOCALIZED ANOMALIES IN HUMAN EMBRYOS
ve
6:
3
ever, many of these specimens are enclosed in membranes which
have undergone very marked changes.
Thus, an embryo,
normal in form, may be found surrounded by an excessive
amount of magma, and the chorion may have undergone very
pronounced changes; but for purposes of classification we have
found it necessary to arrange them all according to the shape
of the embryo.
TABLE 3
Ecotopic specimens
A fairly large number of our specimens were
Dp
a
Bipesrenocme Ha ol a Iwate di % | na | | 2213) aeleselmenli |ie3oluo | to | a
= NUMBER = S
1 93. 10) OMOM CONOR OF 0150: 20.04 sO: Osos ROR OO) 170/10; 0
Zin 09-2055 COP TON ONO EO 2) | -04) SL We eOa RON OR KONO! 0) IS
Si 206=295) 0) C1 OO) Or) O10! 0 0.1 | L POR ROR FON OR On) 0") 0.) 2
Be 296-380) 9) (0) 4) de Dae ely et) 95.0. 125 | 08| OF ON POS ROO: 120! "0. | 2
Sessl tone 3) LEO OOS Onl db 1)0 [4 | SonOR On OP On O 0) 0 4110
Gero SHO 2 Oo 252 Wed 122-| 0) 3.) 25) Or Omen 010% | 07) 6
Mibece-co2e Weal NO Os) On Or On) 3 | 0 [4.5/0 ORO ROR Or O50") O74
Sio520-729° 1 3) 3) 010 2 10 (1 ).9 1.015 | 0 10 NO WRO RG On) 04 0) 5
Sie wo0—sLob) 6) 8) Or O10) | To i16. 0: | A | OO Oe Onno O10. 50") 4:
TOP RS tc—OO0S ti AO) al 2 27 Oe) 82) So Os MOOS ONVOnl"0150) | 6
2A|32| 3.1 3 | 8 | 6 | 7 838.) 0 |82 110 |°2 10/0) 0) 0) 0 | 0 44
TABLE 4
Specimens showing localized anomalies to be compared with table 1
L PATHOLOGICAL NORMAL
z CATALOGUE
2 NUMBER = =
Z| E23) Ae oe 06 7 8 fT | 2. | ose eee 7 | 8 || Sallie |S
3) A G
1 19821) OOO Os OL WT 2 4 Os OR Os O107)20: 0°) °0. | 5
Ain 992052 || FOMOMOT POR ht 2 1 | AOS sO eOn Or OniGe sO! |O: is
Bevo 20a VOM OM ON Olde | at Se Sel Sea O OOS Ou OF: Or) i
Ae 96-3508 MOP OOO es | Le 0: bo Oneal A ONO)! O 121.6
Socio. NPOROMON EO yh 12.110: 3: | O OO Oe 0.1 -OF 1 001'0"|..0: 1,071.0
Cheeni ore TOO O On OP 2510) 2> | OSs Om MONO! | OPNO- I On Or! 4.
7 Bie -OoZce sO OOM MOM Os ara 5a ON ezn eOm On On Om On Oo Os eOnme2
Se Gocd—i20 Ol OON Os) 2) | 0: 1-0) 92.) OP aes 20") O |-0' 190-| 0%) 0: 10 4 1
FOO eC MINOR On ide iese io) i Otome 2.1! O: 10s! 0), O05 /0" (6
ot oe OOO Dee 2 OL) sa Or) O50 O07 0.) 0.) 0 | 0173). 3
QO} 0] O | O {11 |13 [14 [388 | 2/22} 3)4)/0)1)0]1) 0) 4 |37
64 FRANKLIN P. MALL
obtained from hysterectomies, and we believe with Hochstetter
that we shall ultimately have to determine what constitutes a
normally formed human embryo from specimens obtained in
this way. However, even by this method we have found among
about 25 specimens 3 markedly pathologica] ones undergoing
abortion.
The second table includes all specimens that were obtained
from the uterus, and the third, all ectopic specimens. ‘Thus,
in making a comparison of these three tables it will at once be
noted that among the entire 1000 nearly 40 per cent are patho-
logical embryos and ova. Of this number, 31 per cent were
obtained from the uterus alone while slightly more than 8 per
cent were ectopic. The comparative frequency of pathological
and normal embryos can be ascertained, however, by comparing
them within a given century, or for the whole thousand to-
gether. In the uterine specimens about one-third of the ova
and embryos are pathological, as compared to two-thirds in
the actopic. In other words, pathological specimens are twice
as frequent in ectopic as in uterine pregnancy.
The fourth table includes all the specimens in which there
are pronounced localized anomalies. The character of the
anomaly is given with the individual specimens which are re-
corded in tables 5 and 6. It is interesting to note that these
tables show that there are about as many anomalies among the
normal as among the pathological specimens, but when these
figures are compared with the total of specimens both normal
and pathological, it becomes evident that localized anomalies
occur about twice as frequently in the pathological as in the
normal embryo. ‘Thus, there are 38 localized anomalies among
396 pathological specimens or about 10 per cent, while the oc-
currence of localized anomalies in 604 normal specimens is about
6 per cent. The table shows further that the 38 pathological
specimens with localized anomalies abort in the early part of
pregnancy and only one of them (No. 649) grew to a sitting
height of 90 mm., that is, about the middle of the fourth month.
Among the normal embryos, those with localized anomalies
usually disappear before the fifth month, there being but one
in the sixth, one in the eighth, and four in the tenth month or
GROUP
Group 5
(Cylindrical
Embryos)
Group 6
(Stunted
Embryos)
Group 7
(Macerated .
and fetus
compressus)
TABLE 5
Localized anomalies in pathological embryos
CATALOGUE
NUMBER
LENGTH OF
EMBRYO
DIMENSIONS
OF CHORIN
15x12x10
35x30x20
28x25x15
60x25x25
25x20x15
29x23x16
80x50x35
95x55x55
27x25x15
35x35
60x45
70x35x35
65x55x35
45x45x45
90x50x40
45x45x40
80x60x50
90x75x50
65x35x35
19x26x16
60x60x50
70x45x45
80x50x35
75x60x50
90x60x50
65
MENSTRUAL
AGE
bo
bho
o2)
49
35
80
89
88
87
193
THE AMERICAN JOURNAL OF ANATOMY, VOL. 22, No. 1
LOCALIZED ANOMALY
Spina bifida
Hydrocephalus
Spina bifida
Hydrocephalus
Hydrocephalus
Spina bifida
Hydrocephalus
Eye detached from brain
Amyelia-Ectopia of heart
Amyelia
Anencephaly—Spina bifida
Hydrocephalus
Spina bifida
Spina bifida
Spina bifida
Anencephaly
Anencephaly
Rounded head—Club leg
Exencepahaly—Hare lip—
Exomphaly—Spina bifida
Hare lip—Spina bifida
Cyclopia
Club foot and hand
Club foot and hand
Spina bifida—Exomphaly—
Without radii and without
thumbs
Head defective—Spina
bifida
Anencephaly
Head atrophic
Exomphaly
Spina bifida
Anencephaly—Spina bifida
Spina bifida
Club foot
Club hand and foot.
adherent to head.
Skin nodulas
Club hand and Club foot
Club foot
Club hands and feet
Club foot
Exencephaly
Hand
TABLE 6
Localized anomalies in normal embryos
MONTHS
1
(O-25mm. )
2
(2.6-25mm.)
3
(26-68 mm.)
4
(69-12 mm.)
CATALOGUE
NUMBER
OF CHORION
LENGTH OF
EMBRYO
DIMENSIONS
mm. mm,
2 10x9 x8
2a 18x18x18
5 | 16x14x12
7
ofS: 17x17x10
5 25x20x15
a
4
5 24x18x8
6
6
6
40x28x28
35x20x17
30x20x15
6.6
i 25x20x15
8 20x15x12
14 38x32x32
18 45x45
23 50x50x70
23 50x50x70
40x40x40
bo bo
ee He Be
50x30x20
bo bk bo
OU
50x42x40
ow w
(SE S|
66
MENSTRUAL
AGE
a
a
c~
a
ye
—
i
HS
47
52
48
54
117
LOCALIZED ANOMALY
Cytolysis
Anencephaly—Spina bifida
Spina bifida
Spina bifida
Anomalous tracheal diver-
ticulum
Hydrocephalus
Spina bifida
Deformed tail
Spina bifida
Spina bifida
Leg hypertrophic—Head
atropic
Hydrocephalus
Spina bifida
Cyclopia
Spina bifida
Constricted cord
Spina bifida
Double monster
Double monster
Cyst of spinal cord
Hernia of liver
Hernia of liver
Atrophic head
Hernia of liver
Double monster
Double Monster
Extremities deformed—Left
radius probably absent.
Head acbophie
Stub coceyx
Left forearm and hand
wanting
Only 2 fingers on right
hand
Pounded head—Thickened
scalp
LOCALIZED ANOMALIES IN HUMAN EMBRYOS 67
TABLE 6—Concluded.
a = z s 2
Pa oe 5° re)
MONTHS 68 me a es LOCALIZED ANOMALY
zB | 83 ze a 8
5% Za 26 ae
o = a a
mm. mm days
5
(122-167 mm.) No specimen
6
(168-210 mm.) 335 | 190 Anencephaly
7
(211-245 mm.) No specimen
8
(246-284 mm.) 558 | 250 Spinia bifida
9
(285-316 mm.) No specimen
(| 370 After birth Enormous tail
10 862 At birth Eetopia of bladder
(317-336 mm.) 862a At birth Spina bifida
i 862b At birth Stunted eyes
at the end of pregnancy. In other words, all pathological speci-
mens, either with or without localized anomalies, abort in the
first half of pregnancy; while nearly all so-called normal embryos
with slight malformations are also aborted before the middle of
pregnancy, very few of them reaching full term.
We have made an especial effort to collect specimens of full
term monsters as well as abortion material from all months of
pregnancy. Only the first 100 specimens of the collection show
an unusually large percentage of normal embryos. Although
at first an effort was made to collect only good normal specimens
the last 900 specimens, including all sorts of material, of the
collection carry about the same percentage of normal speci-
mens throughout. The first 1000 specimens of our collection
is short of fetuses from the second half of pregnancy, but we
are now endeavoring to collect material covering all months of
FRANKLIN P. MALL
o>)
1o2)
pregnancy. One monster at term, a sympus belonging in
about the third hundred, was not recorded in our catalogue,
and should be added to the four full term specimens given in
table 4. This means that among 1001 specimens there were
five monsters at term, while among 1000 specimens there were
71 with localized anomalies, most of which were aborted early
in pregnancy.
According to the table on the frequency of abortions given in
my monograph on monsters,® there are 80 full term births for
each 20 abortions; therefore, the 1000 abortions under considera-
tion were probably derived from 5000 pregnancies.
As we have calculated that there should be approximately 30
full term monsters in 5000 pregnancies, and as 5 of these were
observed in our 1000 specimens, it is apparent that the remain-
ing 25 should be encountered in 4000 additional full term births.
When these figures are compared with the fact that 75 localized
anomalies occurred in 1000 abortions—7.5 per cent, it becomes
apparent that in any similar numbers of abortions, localized
anomalies should be noted twelve times as frequently as mon-
sters at term. A similar result is obtained if the number of
localized anomalies of the tenth month, as given in table 4, is
compared with all of the localized anomalies of previous months,
as given in the same table.®
Our studies seem to justify the conclusion that pathological
embryos, as well as those which are normal in form, are very
frequently associated with localized anomalies and that abortion
usually follows as a result of serious lesions in the chorion, as
well as in its environment. Should the alterations in the em-
bryo and in the chorion be very slight, and the condition of the
uterine mucous membrane, which may be expressed by the
term inflammation, be overcome, the pregnancy in all proba-
bility would go to term and end in the birth of a monster or
an infant presenting a well recognized malformation.
® Also in a résumé of the paper on monsters in the article entitled: Mall, F.
P. Pathology of the human ovum. Chapter 9, Human Embryology, Keibel and
Mall, vol. 1, 1910.
® Records are now being made of about 50,000 births in Baltimore, including
the frequency of abortions for each mother. When these are completed, the
above mentioned ratio of 1 to 4 will probably be changed.
LOCALIZED ANOMALIES IN HUMAN EMBRYOS 69
I have already pointed out the difference in, frequency of
malformations and destructive changes as observed in the ovum
in tubal and in uterine pregnancies. Since the publication of
my monograph on monsters, I have reconsidered the question
of tubal pregnancy, and the specimens mentioned in the present
paper are recorded in detail in a book on tubal pregnancy re-
cently published.?
It seems to me that the studies based upon our collection of
embryos as well as recent investigations in experimental embry-
ology, set at rest for all time the question of the causation of
monsters. It has been my aim to demonstrate that the em-
bryos found in pathological human ova and those obtained
experimentally in animals are not analogous or similar, but
identical. A double monster or a cyclopean fish is identical
with the same condition in human beings. In all cases, mon-
sters are produced by external influences acting upon the ovum;
as, for instance, varnishing the shell of a hen’s egg or changing
its temperature; traumatic and mechanical agencies magnetic
and electrical influences, as well as by alteration of the character
of the surrounding gases, or by the injection of poisons into
the white of an egg. In aquatic animals, monsters may be
produced by similar methods. Whether in the end all malfor-
mations are brought about by some simple mechanism, such,
for instance, as alteration in the amount of oxygen or some other
gas, remains to be demonstrated. The specimens under con-
sideration show such marked primary changes in the villi of the
chorion and in the surrounding decidua that the conditions in
the human may be considered equivalent or practically identical
with those created artificially in the production of abnormal
development in animals.
It would have been quite simple to conclude that the poisons
produced by an inflamed uterus should be viewed as the sole
cause, but when it is recalled that pathological ova occur far
more commonly in tubal than in uterine pregnancy, such a
theory becomes untenable. Moreover, monsters are frequently
7 Mall, Franklin P. On the fate of the human embryo in tubal pregnancy.
Publication No. 221, Carnegie Institution of Washington, 1915.
70 FRANKLIN P. MALL
observed in swine and other animals without any indication of
an inflammatory environment. For this reason I have sought
the primary factor in a condition buried in the non-committal
term faulty implantation. It would seem to be apparent that
lesions occurring in the chorion as the result of faulty implanta-
tion, can and must be reflected in the embryo. For example,
before circulation has developed, in a human embryo, pabulum
passes from the chorion to the embryo directly through the
exocoelom, and probably on this account we always encounter,
as a first indication of pathological development, a change in
the magma. In older specimens before any other changes are
noticeable in the ovum, the magma become markedly increased,
and a variety of changes are found between the villi. I shall
not dwell further upon magma as I have recently dealt with
the subject in detail.’
It is perfectly clear that monsters are not due to perniinal
and hereditary causes, but are produced from normal embryos
by influences which are to be sought in their environment.
Consequently, if these influences are carried to the embryo by
means of fluids which reach it either before or after the circula-
tion has become established, it would not be very far amiss to
attribute these conditions to alterations in the nutrition. of the
embryo. Probably it would be more nearly correct to state
that change in environment has affected the metabolism of
the egg. Kellicott, who has recently discussed this question,
seems to be disinclined to accept such an explanation, but I do
not see that he has added materially to it by substituting the
word disorganization for nutrition as one might as easily say
that the altered nutrition causes the disorganization.?
In my paper on monsters I stated that on account of faulty
implantation of the chorion the nutrition of the embryo is af-
fected, so that, if the ovum is very young the entire embryo is
soon destroyed, leaving only the umbilical vesicle within the
8 Mall, Franklin P. On magma réticulé in normal and in pathological de-
velopment. Contributions to Embryology, vol. 4, Publication No. 224, Carnegie
Institution of Washington, 1916.
9 Kellicott, W. E. The effect of lower temperature upon the development of
Fundulus. Am. Jour. Anat., vol. 20, 1916.
LOCALIZED ANOMALIES IN HUMAN EMBRYOS 71
chorion, and this also soon disintegrates, leaving only the chor-
ionic membrane which in turn collapses, breaks down and finally
disappears entirely. In older specimens, on the other hand,
the process of destruction takes place more slowly and thus we
account for a succession of phenomena which correspond with
the seven groups of pathological ova recognized and given in
the various tables appended.
In my original study, I really went, I believe, a step farther
than Kellicott in his discussion of monsters, as he dropped the
subject by stating that the embryo is a monster simply because
it is disorganized. I attempted to analyze the process of dis-
organization more thoroughly and demonstrated that when
disorganization begins it is accompanied by cytolysis, but as
it progresses more rapidly it results in histolysis, and that these
_ two processes do not act with equal severity on all parts of the
embryo. When we consider the whole ovum, it is the embryo
itself which is first destroyed; while within the embryo the cen-
tral nervous system or the heart is the portion which is first
affected. Morphologically, these changes are accompanied by
a destruction of certain cells and tissues, leaving other portions
which continue to grow in an irregular manner. For this reason
I speak of the tissues which are first affected as more susceptible
than the others. The entire process of disorganization, result-
ing in an irregular product, I have termed dissociation. In
a general way this explanation is accepted by Werber in his
recent studies, but he employs the term blastolysis instead.!°
At the time I prepared my paper on monsters, Harrison was
just beginning his interesting experiments in tissue culture in
our laboratory. Since then this method of study has given us
clearer insight into the independent growth of tissues. I was
fully convinced from the study of pathological embryos that
tissues continue to grow in an irregular manner, thus arresting
normal development; but since we are more familiar with the
10 Werber, E. I. Experimental studies aiming at the control of defective and
monstrous development. A survey of recorded monstrosities with special atten-
tion to the ophthalmic defects. Anat. Rec., vol. 9, 1915. Also: Blastolysis as
a morphogenetic factor in the development of monsters. Anat. Rec., vol. 10,
1916.
72 FRANKLIN P. MALL
growth of tissues, as revealed by Harrison’s method, we can
understand a little better the process of dissociation. In fact
we have in our collection two striking examples of tissue culture
in human embryos. In one, the cells had formed an irregular
mass which is growing actively, but the contour of the organs
has been entirely lost. In the other, from a tubal pregnancy,
for some unknown reason, the ovum had been completely broken
into two parts, which in turn had cracked the embryo, and from
each piece had been a vigorous independent tissue growth, or,
as we may now say, a tissue culture. Accordingly, when an
embryo through changed environment is profoundly affected,
the development of one part of the body may be arrested, while
the remaining portion may continue to grow and develop in
an irregular manner. In very young embryos tissues or even
entire organs become disintegrated, as can easily be recognized
by the cytolysis and histolysis present, and the resultant dis-
organized tissue cannot continue to produce the normal form:
of an embryo. If this process is sharply localized, for instance,
in a portion of the spinal cord or in the brain, spina bifida or an-
encephaly results. To produce a striking result, as in cyclopia,
a small portion of the brain must be affected at the critical time,
and I think the work of Stockard has shown clearly that this
is before the eye primordia can be seen. Consequently, in
order to produce a human monster, which is to live until the
end of gestation, the altered environment must be reflected
from the chorion to the embryo, so that the tissue to be affected
is struck at the critical time in its development. It is incon-
ceivable that cyclopia should begin in an embryo after the eyes
are once started in normal development. Moreover, the same
is true regarding hare lip, for after the upper jaw has once been
well formed, the abnormality cannot develop. We may extend
this statement to include club-foot, spina bifida occulta, and
other types of malformation. In fact, in discussing the origin
of merosomatous monsters, hardly more has been stated by
most authors than that there has been an arrest of development,
but I have attempted to point out that the primary cause is in
the environment of the egg and that the arrested development
is associated with destruction of tissue.
CYTOLOGICAL OBSERVATIONS ON THE BEHAVIOR OF
CHICKEN BONE MARROW IN PLASMA MEDIUM!
RHODA ERDMANN
Osborn Zoological Laboratory, Yale University, New Haven, Connecticut, and
Rockefeller Institute for Medical Research, Department of Animal
Pathology, Princeton, New Jersey
TWO TEXT FIGURES AND NINE PLATES
The writer, employing the bone marrow of the chicken for
attenuating the virus of cyanolophia (Erdmann ’16?), by culture
of the marrow and the virus in a medium of chicken plasma,
has observed some interesting facts concerning the cytological
changes in the bone marrow cells.
The morphology and development of chicken bone marrow
and its relation to blood formation have been described by few
authors. Dantschakoff (09, pp. 859-65) gives an extensive
review of the literature on these questions and establishes our
knowledge of the origin of the different elements of chicken bone
marrow.
In studying the cells of bone marrow in plasma culture
medium, we must take into consideration the fact, that we add
to the plasma in which the tissue culture is cultivated a hetero-
geneous mixture of highly differentiated cells. Chicken bone
marrow has a loose framework of slender connective tissue
cells, in the meshes of which blood and fat cells are scattered.
The blood cells—eosinophils, erythrocytes, and myelocytes—
form, according to Foot (’13, p. 45) strands and circles between
and around the fat cells. The blood islands represent collec-
tions of cells of microlymphocytic and macrolymphocytic types,
of more or less ripe erythrocytes and of young connective tissue
cells. It must be clearly kept in mind that all these different
1 Received for publication March 14, 1917.
2Erdmann, Rh. 1916 Attenuation of the living agents of cyanolophia, Pro-
ceedings of the Society for Experimental Biology and Medicine, vol. 8, pp.
189-193.
73
74 RHODA ERDMANN
elements behave differently in the tissue cultures and may,
after having undergone important changes in the plasma, offer
some difficulties in interpretation.
The only observations of normal chicken bone marrow in
plasma are those made by Foot 712 and ’13. In the first series
of experiments he studied especially the behavior of the fatty
elements of chicken bone marrow, recording the following re-
sults. Six hours after implantation numerous cells leave the
tissue center. They form rays of cells liquefying the plasma.
These rays are formed by polymorphous leucocytes with eosin-
ophile granules and by ‘“‘eine Art von mononukleiren basophilen
Zellen” (p. 450). Foot gives the latter the name of X cells;
they are the most important and they contain only fat accord- .
ing to his observations of 1912. They form, he says in 1912,
the bulk of all cells migrating into the surrounding plasma.
These X cells, the origin of which Foot tries to elucidate, are
true phagocytes They include small fatty droplets and other
particles which are dispersed in the cytoplasm. On the fourth
day, these cells, after having been enlarged by the amount of
fat which they have taken up during the first three days in the
culture, form either syncytial masses or a widely spread network
of anastomosing cells. The former may divide, after having
lost most of their fatty granules, and form the final ‘ruhende
X Zelle’ (Foot ’12, fig. 8, pl. 22): or the latter, after having been
highly vacuolized, as stated by Foot ’12, may form fibrils
(fig. 18, pl. 22). If these X cells do not form resting X cells or
cells which produce fibrils, they take the shape of ‘Riesenzellen.’
These ‘Riesenzellen’ are not identical, in Foot’s opinion, with
the ‘giant’ cells of the normal bone marrow. ‘They are repre-
sented in his figures 11, 16, 17, 19. They are only X cells which
have fused together, form no fibrils, and may later break up in
small cells (figs. 12 to 14), which have generally one nucleus.
‘“‘Das Ergebnis der Aufteilung der Riesenzellen ist sozusagen eine
neue Zellrasse”’ (p. 460)—cells adapted to the condition of the
medium.
Foot believes that the X cells are transformed cells of the
‘mesenchyme’ and ‘‘Zwar indifferent gewordene Mesenchymzel-
lor Ald
CHICKEN BONE MARROW IN PLASMA MEDIUM (o
len”’ (p. 466). He reasons as follows: Because these cells have
the potentiality of forming fibrils they must belong to those
cells which can form connective tissue, and therefore these X
cells without any intermediate stages take their origin from
mesenchymal or endothelial cells. In a postscript to this paper
he changes his opinion entirely and says (p. 475): ‘‘Was die
Herkunft der X Zellen betrifft, so scheint es als ob die Haupt-
masse derselben entweder direkt oder indirekt von den lympho-
eytiren oder myeloblastischen Elementen des Knochenmarkes
abstammte,’’ promising to give the reasons for this change of
opinion in his second communication.
After a careful study of Foot’s second at eon (13),
which is rather difficult to understand because he does not very
often connect his first publication with the second, I restate in
his own words his revised opinion of the origin of those cells which
form X cells (18, pp. 46-47). ‘‘The deductions as to the trans-
formation of the lymphocytes from one form to another, which
form the basis of the following descriptions, were made from
the observation of transition forms. ‘The later transformations
of these cells into forms resembling fat and giant cells or cells
of the connective tissue have been considered in my pre-
vious article.”’ So it appears that the so-called X cells of this
author (’12)—the name does not often appear in the paper of
1913—are not directly transformed cells of the mesenchymal
type but are said to be of lymphocytic origin. He observes
that as early as three hours after implantation of the bone
marrow a considerable number of microlymphocytes emigrate
from the tissue particle. Their transformation occurs in the
following way:
~The small microlymphocytes are first transformed into ma-
crolymphocytes, later into large mononuclear forms, then into
myelocytes. At last the polymorphonuclear leucocytes appear,
after having undergone different changes in the form and struc-
ture of the nucleus. The nucleus is at first horseshoe-shaped,
later polymorphonuclear and even polynuclear. Finally the
cells, by rounding off and dechromatization of the nucleus
coincident with the rarification and a change in the staining
76 RHODA ERDMANN
properties of the plasma, are transformed into the cell culture
type (p. 56). This cell culture type (see his fig. 2, pl. 3, and his
fig. 3, pl. 4) represents small polymorphonuclear leucocytes
(p. 49) which have undergone the transformation, but not only
does the cell culture type originate from lymphocyte forms, but
this ‘stem cell’ can also be transformed through the transition
stage of amoeboid forms into ‘giant cells,’ syncytia, and, as said
before, into the cell culture type (table 1, p. 56).
Thus it is clear that, according to this author’s view, all the
different forms described by Foot in 1912 and 1913 originate
from the microlymphocytes. Until the present time (16) this
important fact lacked verification, but by the cultivation of the
virus of cyanolophia in chicken bone marrow an opportunity
was afforded of observing the changes which Foot describes. <A
careful study of the morphological and cytological characters
of the cells figured in the above mentioned papers, soon showed >
a lack of transition stages, which are needed as proof of Foot’s
final theory. Further, the nuclei of cell forms which are said
to be transformed into each other do not show close resem-
blances, e.g., the cells in figures 1 and 3, 1913, which are said to
be eosinophil leucocytes at different stages of incubation, have
different nuclear structure as well from each other and from
the cell of the cell culture type (fig. 2, left side, 1913). The
nuclear structure of this particular cell (fig. 2, left side, 1913),
however, has a certain resemblance to the nuclei shown in 1912,
figures 5 and 6. These cells are considered by Foot as stages
connecting the ‘Riesenzellen’ with ‘‘eine Art von monnukledren
basophilen Zellen” (1912, p. 450). But here, as far as could
be judged from the drawings, the cytoplasm of the cells in
figures 5 and 6 is very different. Figure 5 has granules, figure
6 does not show them; only traces of digested nuclei of other
cells are visible. These contradictory facts present @ priori
difficulties in accepting the views of Foot. But they appeared
far more disconcerting on examining the cells themselves.
CHICKEN BONE MARROW IN PLASMA MEDIUM ced
TECHNIQUE OF CULTIVATING, PRESERVING, AND STAINING BONE
MARROW
It is not necessary to describe in detail the technique of these
cultures, since the writer followed the same methods as those
used by Harrison (10), Burrows (711), and particularly Foot
(12 and ’13). For storing the plasma it was deemed important
to use the methods described by Walton (’12) for keeping mam-
malian plasma in good condition for long periods of time. Great
stress was laid on the study of the living cells, and a warm stage
was used to follow out the transitions of one cell form into
another. The bone marrow of very young chickens, those of
medium age, and of old individuals was studied; observations
were also made on bone marrow which contained a very small
amount of fat, as well as that which had a large amount of fat.
The method described below gave the best results in identify-
ing and showing the stages of the individual cell types in stained
preparations. A small particle of bone marrow was put into
the plasma medium. The cells in the tissue were then allowed
to migrate out of it. At periods of either 2, 4, 6, 12, or 24 hours,
the original particle of bone marrow was extracted, and the fate
of those cells which had emigrated was studied. The writer
found that from the original particle of tissue numerous cell-
forms had been sent into the surrounding plasma clot. Having
thus extracted the bone marrow, it could be determined with
absolute exactitude which cell-forms emigrated first, and the
history of those cell types which had emigrated after 2, 4, 6, 12,
or 24 hours, or at any given period, could be recorded. ‘The
extracted particle of bone marrow was now transferred to a new
plasma medium and the cell forms which emigrated after the
transfer were also observed. This was repeated several times,
until practically all emigration of cells into the surrounding
plasma had ceased. The structure of the remaining particle of
bone marrow was of course studied. Smears and sections were
made at every stage of the emigration process and a more com-
plete history of this complicated process was thus obtained.
In staining the pieces of bone marrow, the methods used by
Foot in 1912 and 1913 were followed and other methods for the
78 RHODA ERDMANN
discovery of fat were added (see descriptions of plates, page 118.
Besides these, the Giemsa stain after moist fixation according to
the prescription of Giemsa proved to be very satisfactory. No
dry smears of bone marrow were used.
THE FATE OF LIVING BONE MARROW CELLS IMPLANTED IN
PLASMA AT 38°C,
The experiments from which the drawings on plates 1 and 2
were made were started on December 25, 1915, and on January
3, 1916. The bone marrow was taken from a full-grown chicken
which had a large amount of fat, so that the pieces of marrow
have a yellowish-white appearance. ‘The first cells to leave the
tissue after 40, 60, and 90 minutes incubation are, as Foot
rightly remarks in his publication of 1913 (p. 49), small
mononuclear or larger polymorphonuclear leucocytes (fig. 1).
The forms have a very dark, granulated cytoplasm and are
actively amoeboid (fig. 1). Pale mononuclear forms without
granulations but with their characteristic vesicular nucleus,
follow closely the emigrating polymorphonuclear leucocytes.
The fourth cell from the left (fig. 1) represents an erythroblast.
The structure of the nucleus makes this evident. Besides these
forms figured in figure 1, red blood corpuscles and a few fat
cells were present in those parts of the plasma clot which sur-
round the implanted bone marrow particle. The network of
the bone marrow was injured by the process of cutting and tear-
ing the particle into small pieces, and it is therefore not sur-
prising that a large number of red blood corpuscles and some
fat cells were scattered into the surrounding plasma clot. They
are not figured in figure 1.
After 24 hours various other cell types have migrated into
the surrounding plasma.
Figure 2 shows bone marrow which has been in the plasma
for 24 hours, from January 3 to January 4, 1916. We can easily
distinguish two different kinds of granulocytes: big cells which
have round, shining granules, the nucleus nearly half as big as
the cell and half-moon shaped; and smaller forms, with very
dark granules, the latter not rounded but more rod-shaped, the
CHICKEN BONE MARROW IN PLASMA MEDIUM 79
nuclei spherical and very often dividing. It is impossible to
define without doubt the exact type of these granulocytes before
the relation of their granules to basic or acid stains develops
the true character of these cells. Therefore we do not venture
any interpretation of the bigger type of these granulocytes but
point out only that the smaller forms must be eosinophil leuco-
eytes after their morphological structure, though their granules
appear rather darker than those in non-incubated leucocytes of
chicken-bone marrow. Also they have less distinctly round or
less rod-shaped granules. These two observations are important.
The big cell in the center of the figure 2 does not contain any
granules but is from the large nongranular mononuclear lympho-
cyte type. Very often these cells break into pieces during ob-
servation.
Two other cells, one on the right, the other on the left side of
figure 2 are of a different type. They contain large shining
droplets, the fatty nature of which seems doubtless. Their
nuclei have a vesicular structure and appear at this stage of the
culture as often dividing. They are less numerous than the
eosinophil leucocytes which form, in the first 24 hours, the bulk
of all cells migrating into the surrounding plasma medium.
Figure 3 represents bone marrow which has been incubated
for 48 hours (January 3 to January 5, 1916). Here a ‘Riesen-
zelle’ is rapidly moving; its cytoplasm is spread over a great
area on the cover-glass and contains fat droplets and glisten-
ing granules. This ‘Riesenzelle’ shows in its cytoplasmic
structure a close resemblance to the fat droplet containing cells
on figure 2. To account for the larger size, we can either sup-
pose that several of these cells have fused together or the cyto-
plasm of a single cell is thinned out by the method of cultivation.
The structure of the granulocytes is not very much changed.
The larger forms with glistening granules and half-moon-shaped
nucleus have diminished in number but smaller cells of the same
type can be discovered now and then. In these forms some-
times fat droplets are visible. The eosinophil leucocytes are
still abundant, but are surpassed in number by small ungranu-
lated cells. These form now the bulk of the cells migrating into
SO RHODA ERDMANN
the surrounding plasma clot from the implanted tissue particle.
They have either vesicular, less refractive or very shining and
highly refractive nuclei.
In plate 2 we can follow in detail the further changes of the
‘Riesenzellen.’ The bone marrow (fig. 4) has been implanted °
72 hours, from January 3 to January 6, 1916. Three round
cells with big fat droplets can be seen, which seem to protrude
out of the cell or cover its surface. The nuclei are therefore
very seldom visible. When visible, they appear dark. <A few
granules are contained in the cytoplasm besides round or ir-
regularly shaped masses, which seem to be remnants of other
cells. On the third day after implantation these cells im-
mediately attract the attention of the observer. They seem
to have taken the place of the ‘Riesenzellen;’ this could
be demonstrated by observation of the living cells. Some
‘Riesenzellen’ break apart, take on a round shape and com-
pletely extrude the fat droplets. These may be small or larger
(fig. 5, second cell, left side) and show very fine pseudopodia.
They are round cells which can survive an indefinite time in
the plasma medium, the so-called ‘cell culture type.’
Many ‘Riesenzellen’ however (fig. 5), the similarity of which
to the round cells seen in figure 4 can be easily discovered, show
all signs of degeneration. The cytoplasm has a ‘curdled’
appearance and is torn. The fat droplets have been thrown out
into the plasma clot, and the granules have acquired a dark
appearance. ‘This regressive process takes place on the fourth
or fifth day after implantation. These decaying cell masses
are surrounded by small’ granulated and ungranulated cells
and seem to be able to phagotise, because their cytoplasm shows
in some places ‘curdled granules.’
During the next days of incubation, no striking changes take
place. The number of living cells diminishes and few types
of cells are in healthy condition.
Fig. 6 shows cells which have been incubated in the same
plasma medium 216 hours (from December 25 to January 3).
They have small distended nuclei which do not seem to contain
much chromatin, and the cytoplasm is filled with shining
CHICKEN BONE MARROW IN PLASMA MEDIUM 81
droplets. They belong to the so-called ‘cell culture’ type.
Besides these cells we find others with oblong nuclei and elon-
gated cytoplasmic bodies full of glistening fine granules. These
move slowly and show fine pseudopodia formed by their
delicately granulated cytoplasm.
To summarize: Fat containing bone-marrow of chicken when
incubated for 9 days in a plasma medium, undergoes the fol-
lowing changes which can be observed in the living preparation:
The signet-like fat cell disappears, it is transformed to ‘Riesen-
zellen’ and finally to the ‘cell culture’ type. This type includes
round cells with coarsely granulated cytoplasm, big shining
droplets and oblong, less refractive nuclei. The other prevail-
ing cell-form is distinguished by its finely granulated cytoplasm,
elongated or round cell body, and oblong nucleus.
These two cell types (not widely different in their morpho-
logical bearing) are always to be found among the cells which
have migrated from the implanted bone-marrow particle into
the plasma clot. Besides these cell forms,—capable as it seems
of metabolism for long periods,—we see all forms of disinte-
grated cells. The cytoplasm and nucleus separate and the
preparation is filled with débris. Fat droplets of different
sizes which are freed from the cell fill the preparation. Nuclei
of small granulocytes and lymphocytes without cytoplasm are
often seen. Also shadows of blood corpuscles and granulocytes
of all sizes are present.
It is certain that in non-renewed tissue culture retrogressive
and progressive processes take place. It will be necessary to
investigate the more intimate phenomena of these changes in
stained preparations specially adapted to the study of each dif-
ferent cell type by different methods of cultivating and staining.
THE FATE OF THE MONONUCLEAR AND POLYMORPHONUCLEAR
EOSINOPHIL LEUCOCYTES OF THE BONE MARROW IN
TISSUE CULTURE
While describing the changes of the living bone-marrow cells
after they had been 1, 24, 42, 72, 96, and 216 hours in the plasma
medium,—the present author could give little or no definite
THE AMERICAN JOURNAL OF ANATOMY, VOL. 22, NO. 1
82 RHODA ERDMANN
interpretation of the changes observed in the different types.
Some exact knowledge could be acquired only by comparing
and combining the phenomena observed in bone-marrow cells
in preserved and stained preparations after they had been in
the plasma medium for, well defined periods.
In figure 7, an exact microscopic field of a bone marrow prep-
aration, after 36 hours incubation, is shown. The implanted
tissue particle would be (Gif shown on the drawing) on the left
side of the preparation. The cells shown have migrated to the
zone next to the implanted bone-marrow tissue particle which.
was taken from a full-grown chicken and contained fat
Kosinophil leucocytes in various developmental stages are
numerous. They are in rapid amoeboid movement, and by
continued fragmentation diminish in size and multiply in
number. Their plasma is slightly basophil. The nuclei are
strongly chromophil and the nuclear leucocytic structure in
most forms is indistinctly developed. By comparing the nuclear
structure with that of eosinophil leucocytes which have been
24 hours in cultivation (fig. 9) we can better distinguish the
typical leucocytic network of chromatin particles and threads.
The plasma of these leucocytes and of those figured in figure 8,
which have been only one hour in the plasma medium, is acido-
phil and the round granulations are very distinctly recognizable.
Besides the changes in the cytoplasm of the leucocytes from
acidophily to basiphily, other phenomena are noticeable. After
one hour and still more after 36 hours incubation, the leucocytes
of all sizes are losing and expelling the granulations. The nuclei
of these forms have either become pale and indistinct (fig. 7,
right side, below) or condensed and strongly chromatic (figs.
12 to 14). They may fade out to mere shadows and disappear.
The farther the polymorphonuclear eosinophil leucocyte ad-
vances into the plasma clot, the more its cytoplasm spreads
out in the tissue culture. The granulations in consequence no
longer appear lying closely together, but seem widely scattered
in the cytoplasm. The leucocytes finally lose their power of
cytoplasmic division. This happens generally on the margin
of the plasma clot where the culture medium is thinly spread.
The horseshoe—or kidney-shaped nuclei separate, become
CHICKEN BONE MARROW IN PLASMA MEDIUM 83
pyknotie and form round, chromatic bodies (figs. 11 to 19).
The acidophil granules become more and.more indistinct, the
cytoplasm is again acidophil, and partly vacuolized. In this
stage, long chains of these forms closely lying together cover
the outer zones of the preparation, giving it a reddish halo.
Later these cells without granules flatten out entirely, lose their
nuclei or their chromatic particles, and undergo total destruction.
To summarize: most mononuclear and polymorphonuclear
eosinoiphil leucocytes with either round, kidney-shaped, or lobu-
lated nuclei, during the first hour of their emigration (fig. 8, and
fig. 43) into the surrounding plasma, divide rapidly. They
form smaller cells with fewer granules and a more basophil
cytoplasm. Later by dividing and moving to the outskirts of
the plasma clot, they finally form rays and layers of partly
acidophil, vacuolized ‘cells’ without nuclei and granules. An-
other group of these eosinophil leucocytes, before diminishing
in size in the zone near the implanted bone-marrow particle,
had extruded its granules at a very early period. They fade
out and leave their more basophil cell bodies in the plasma clot.
The mononuclear or polymorphonuclear eosinophil leucocytes
undergo a regressive development in tissue cultures.
These conclusions agree with the writer’s own observations of
the cells in living preparations. On the first and second day of
incubation the eosinophil leucocytes are numerous and of normal
size (fig. 2, left side, above). On the fourth and the fifth day
the few forms, which have not undergone the flattening-out
process and which have not changed their character, are small,
with fine granules and an ellipsoid nucleus (fig. 5, left side,
below). Foot (13, pp. 49-51), in his account of the changes
of the eosinophil leucocyte in the culture medium, reports that
these cells finally take on the same form as that assumed later
by the large mononuclear lymphocytes, and cannot be distin-
guished from them. With this conclusion the present writer
cannot agree. In figure 8, the emigration of small leucocytes
is shown. The lean, almost fat-less bone-marrow orginated
from a young, not full-grown chicken. After an hour in an
identical preparation the tissue was extracted and only the
emigrated cells were allowed to develop. All cell types which
S84 RHODA ERDMANN
are pictured in figures 11 to 26 are cells which have emigrated
early from the bone-marrow particle, advanced to the border
of the plasma medium, and changed in different ways.
Figures 11 to 19 show the regressive development of the poly-
morphonuclear leucocyte which is inserted in the plasma, either
as a younger form, with spherical nucleus, or as an older form
with kidney—or horseshoe-shaped, or lobulated nucleus always
recognizable because of its acidophil granules. The long chains
of these deformed cells in all transitions are easy to identify in
preparations, where only a few cell types have been allowed to
emigrate into the plasma. Here they never take on the char-
acter of the ‘cell culture type’ (Foot).
When bone marrow is taken from a young, poorly fed chicken
and treated as above described, few ‘mononucledre basophile
Zellen’ emigrate in the first half hour, and the bulk are only
eosinophil leucocytes (fig. 48). If these preparations are allowed
to develop two or three days the rays of cells consist for the most
part of these eosinophil leucocytes and few X cells or forms of the
cell culture type are visible. If the process of extracting and
again implanting the bone-marrow particle is repeated and the
cells of the succeeding emigrations are controlled, few eosinophil
leucocytes are observed in the second and third stage and after
the third implantation approximately no eosinophil leucocytes
are to be seen.
Therefore, no new formation of this cell type from a stem cell
could be observed in the plasma clot, but only a process of
emigration, multiplication, transformation and degeneration of
those forms which were implanted with the bone marrow in the
plasma, clot.
THE FATE OF THE ERYTHROCYTES AND THE ERYTHROBLASTS IN
THE BONE MARROW'IN TISSUE CULTURE?
The general rule for the behavior of cells in tissue culture:
the more they are differentiated, or adapted to certain functions,
2Erdmann, Rh. 1917 Some observations concerning chicken bone marrow
in living cultures, Proceedings of the Society for Experimental Biology and
Medicine, vol. 14, pp. 109-112.
CHICKEN BONE MARROW IN PLASMA MEDIUM , (8d
the quicker they undergo destruction holds true in the case of
erythrocytes. The red blood corpuscles appear often without a
nucleus or without a shadow of a nucleus. The plasma seems
perforated. This indicates that the haemoglobin has disap-
peared. ‘Those cells in which we can trace only the shadow or
a faint remainder of the nucleus are apt to deceive the observer.
The remainder of the nucleus appears like a small parasite but
is nothing more than the nucleus of the cell, as can be proved by
numerous intermediate forms. These bodies resemble the Cabot’s
bodies which are described by Juspa (714, p. 429) in certain
diseases of men. Also the nuclei may become pyknotic in other
forms and the plasma may disappear. Foot (12, p. 461, and
1913, p. 46) notes these same two different ways of degeneration
in erythrocytes. Their dead nuclei or their plasma is often
incorporated into phagocytic cells (figs. 34 and 35) the origin
and types of which will be discussed later.
The non-elongated round or irregularly shaped erythroblasts
have a pale yellowish or colorless plasma (figs. 1 to 3). Well
developed erythroblasts are distinguished when stained by their
wheel-like, highly chromatic nucleus. Unstained cells show a
whitish appearance of the nuclear membrane which seems
crowded with the content of the nucleus and ready to break.
Figures 3 and 7 represent erythrocytes and erythroblasts in vari-
ous stages of their retrograde development. Their plasma-less
nuclei cover the microscopic field and are often seen incorporated
into cells of phagocytic character. Unripe, young erythroblasts
are figured in figure 8. They have larger nuclei in proportion to
their basophil plasma than the erythrocytes and are scattered,
through the tearing apart of the bone-marrow network, in large
quantities into the surrounding plasma. They are recognizable
in stained preparations by the smooth surface of their plasma
and their chromatic nuclei and cannot be confused with ‘eine
Art von basophilen mononucleidren Zellen”’ which, according to
Foot ’12, form the X cells and the cell culture type.
But the difficulty begins when very young, i.e., small cells
characterized in the first day of incubation by their situation
near the bone-marrow network, are to be isolated and cultures
S86 RHODA ERDMANN
from young living erythroblasts and from young basophil cells
with vesicular nuclei are necessary, for deciding different ques-
tions. My experiments only proved, after isolating young cells
near to the bone-marrow network that they underwent no trans-
formation into erythroblasts but showed the phenomena fully
described later on page 94-100 the transformation into cells of
connective tissue cell type. It is naturally not excluded that
erythroblasts—when they are already erythroblasts in a strict
sense—divide in the tissue cultures, but I never could isolate
this cell type with any certainty just at the point in being trans-
formed from its ‘stem cell’ into erythroblasts. This phenome-
non seems not to take place:in tissue cultures.
THE FATE OF THE IMPLANTED MICROLYMPHOCYTES IN TISSUE
CULTURES OF BONE MARROW
The microlymphocytes in chicken bone marrow are found in
great quantities. Their small protoplasmic brim and condensed,
highly chromatic nuclei allow us to distinguish them easily
from the small basophile round cells with vesicular and achro-
matic nuclei, closely situated to the network of the bone marrow.
The microlymphocytes seem to be present in the tissue cultures
from the first day of the incubation of the bone marrow, without
apparent changes, until the last day of cell life in the culture.
But are those the same forms which were incubated or newly
originated forms? ‘The microlymphocytes implanted with the
bone marrow particle must be capable of active movements,
because they are no longer visible in the meshes of the bone
marrow network after several days’ incubation, but are always
present in the plasma clot. In the preparations where only a
few cells are allowed to emigrate and to stay several days in the
plasma medium, the microlymphocytes are widely scattered.
Their own cytoplasm expands in a star-like manner, often
forming long cytoplasmatic rays. After a fortnight in the cul-
ture medium, they have the appearance of forms such as the
cells pictured in figure 25. One cell appears normal; the other
has a torn cytoplasmatice body. Figure 27 shows the remaining
nuclei which will soon undergo complete destruction. Foot
13, page 43, believes that besides numerous microlymphocytes,
CHICKEN BONE MARROW IN PLASMA MEDIUM 87
which die, a large number ‘steadily increase in size’ and either
form cells of the macrolymphocytic type or of the large mono-
nuclear lymphocytic type, ‘‘after the latter has undergone
nuclear enlargement and dechromatization.”’ Foot presents no
drawings of these highly important forms, but considers it
sufficient to record the measurements of microlymphocytes of
different sizes, measuring from 3.5 to 9.6 in diameter. The
nuclear structure of these transition forms is not described by
him. The present author has never seen cells with typical
microlymphocytie condensed nuclei in all sizes, only cells with
vesicular achromatic nuclei in every possible size. In the later
discussion these contradictory reports of Foot and of the present
author must be borne in mind.
Some authors hold the theory that microlymphocytes origin-
ated from the large mononuclear lymphocytes by multiple
simultaneous divisions. Only in very recently incubated tis-
sue cultures, as recorded on page 79 a breaking of large lymph-
ocytic forms into pieces was observed. But the isolated culti-
vating of these small cells afforded no definite results. Multinu-
cleated forms with ragged or torn cytoplasmic structure and
nuclei with highly condensed chromatin may be observed in
the case illustrated, of which three have a condensed chro-
matic structure (fig. 8). The younger the implanted bone mar-
row is, the more numerous these forms appear to be. - They
have a slight resemblance in their plasma to very young connec-
tive tissue cells, as, e.g., Maximow (’10) pictures them in figure
43, from a guinea pig, but they seem to have no connection
with the formation of bone marrow lymphocytes.
To summarize: The microlymphocyte belongs to those cell
types which undergo no progressive development in the tissue
culture.
THE FATE OF THE IMPLANTED MYELOCYTES IN TISSUE CULTURES
OF CHICKEN BONE MARROW
From the first to the sixth day after incubation large cell types
can be observed in the tissue culture of bone marrow when the
experiment is conducted with a full-grown, over a half year old
ehicken. These cell types have, as described on page 79,
SS RHODA ERDMANN
before staining and preserving, a half-moon shaped, or elongated
nucleus, and their plasma is either granulated, or the granules
are invisible during cell life. The cells shown in figure 2, two
granulocytes and one ungranulated large cell, have only been one
day in the culture. The first type appears to divide; we can
observe smaller forms on the following days, with larger granules
than the eosinophil leucocytes possess. The other represented
cell type is a large lymphocyte. These forms may break in
pleces during observation. After six days incubation we dis-
cover in stained preparations the changed form of the myelo-
cytes (figs. 39 to 42). The reddish ripened nucleus of these
forms has all the characteristics of a myelocytic nucleus. But
in eosinazur stains such nuclei are generally supposed to have a
more bluish color. This must be explained by the rising acidity
of the culture medium in growing tissue cultures (Rous, 713,
p. p. 1838-86). The cells in figures 39 and 41 must be considered
eosinophil myelocytes, those in figures 40 and 42 mononuclear
lymphocytes. In earlier stages of their degeneration process
these large forms often have very fine acidophil granules in their
cytoplasma when observed on the second or third day of incuba-
tion; but they are never seen to divide. Their plasma loses its
granulations, flattens out, and vacuolizes. The eosinophil myelo-
cytes and lymphocytes have only a regressive development
in the tissue culture medium.
THE FATE OF THE FAT CELLS OF THE BONE MARROW IN TISSUE
CULTURE
But one observation of the behavior of fat cells in tissue cul-
ture is given by Foot, who writes (12, p. 447,) that the culti-
vation of subcutaneous or subepicardial adipose tissue was
without success, growth of considerable amount could not be
observed. The present writer repeated Foot’s experiments.
Adipose tissue of the omentum of the chicken showed, after
three days incubation, almost a complete disintegration; further,
the formation of few cells of the ‘cell culture type’ and the
survival of connective tissue cells could be observed. It may be
conceived that some connective tissue cells may have originated
CHICKEN BONE MARROW IN PLASMA MEDIUM 89
from fat cells losing their fatty contents and assuming the char-
acter of the known type of connective tissue cells. Or the con-
nective tissue cells, implanted together with the adipose tissue
may have developed and multiplied. This is a separate ques-
tion which has not been sufficiently studied in true adipose
tissue.
The changes of the fat cells of bone marrow in tissue culture,
though not considered by all authors to be real fat cells, have a
great resemblance to phenomena seen in rapidly growing embry-
onic adipose tissue, as Foot remarks (p. 48, 712). But he himself,
neither in 1912 nor in his later publication of 1913, states the
ultimate fate of the implanted, so-called fat cells, which, together#
with the other cells of the bone marrow, are in the culture medium
and are numerous in the white bone marrow of the adult chicken.
The typical signet-ring cell may apparently remain unchanged for
24 hours in the plasma medium, as it is shown on a photograph
(fig. 46, right side, above). But the observed facts do not agree
in most cases with this view. After three hours incubation all
fat cells show still their accustomed shape. The big fat globule
surrounded by a brim of cytoplasm flattens out and the large
globule of fat separates into small droplets. Or the fat cell
divides into two parts, and even a process of budding may be
observed (figs. 29 and 30). If the cell has not divided up, the
fat globule diminishes in size and does not fill the whole cell.
With a specific fat stain it can be shown that the cytoplasm is
fuled with small fat droplets and strands (fig. 28). Later foam-
like masses of cytoplasm, in the meshes of which the fat is easy
to identify, protrude from the cell margin and separate them-
selves partially or totally from their ‘mother cell.’ Cells of
this kind may offer the appearance of cells figure in figure 2,
left side, in unstained preparations. In a tissue culture of 24
hours incubation, preserved with Orth’s fluid and stained with
Giemsa stain; they appear as cells with highly chromatic nuclei,
and perforated cytoplasm (figure 7, right side and figures 33
and 34); also weblike masses, apparently without nuclei, are
frequent (fig. 7) which are often surrounded by microlympho-
cytes and polymorphonuclear leucocytes. Text-figure A gives
QO RHODA ERDMANN
the most striking phases of the activation of a fat cell. The
original fat cell, the fat cell which has extended fine pointed
processes, and the final stage that comprehends cells containing
vacuoles which may still have traces of fat in them. (Compare
cells on figure 2; figure 7, cell right side, above; and figures 45
and 46.)
al
Text fig. A. Fat cells after 6 and 12 hours incubation.
It must be kept in mind that these changes occur during the
first 24 hours or 48 hours of incubation. Figures 45 and 46 show
that in a 30 hours culture the dissolving of the big fat globules
and the dividing up of the fat cells has been in progress. The
cells form chains, typical for the stage of the culture of 24 to 48
hours of fat containing bone marrow. ‘These cell chains flatten
out, fine processes are extruded which cover great areas and
may fuse with other cells in web-like masses. Figures 45 and
46 give a good surview of this process and such a cell is also
represented in figure 33. We note its enormous size, its big
vacuoles, its slender processes, its phagocytic capacity and its
small nucleus. In short, we see a so-called ‘Riesenzelle’ of Foot
CHICKEN BONE MARROW IN PLASMA MEDIUM |
which is already present after 24 hours of incubation. Now
Foot (12, p. 459, fig. 5) gives the photograph of a preparation
of bone marrow after 5 days of incubation in a plasma medium.
This is a descrepancy fer which no explanation could be found.
It is of importance to state that all vacuoles do not contain
fat in such a condition as to make it visible by the osmium
process. The cell (fig. 32) shows still some fine traces of fat,
but in many preparations which were treated with Scharlach
or Sudan stain after adequate fixation, the vacuoles were devoid
of fat. It is conceivable that fatty acids or other products of
related character fill the vacuoles, but even after trying the
most complicated stains (Ciaccio, Benda) to elucidate the
nature of the contents in the vacuoles, no final decision could
be reached.
From the third to the fifth day, the number of ‘Riesenzellen’
has diminished; we see smaller round or oblong cells with one
or several vacuoles, with oblong faintly chromatic nuclei (fig.
34). They are the products of the breaking up of the ‘Riesen-
zellen’ and seem to be identical with Foot’s cell culture type.
They are capable of phagocytosis and move slowly toward the
periphery of the plasma clot.
How can we interpret these extraordinary changes in the
fat cells? The only similar observation was made by Maximow
(04, p. 108), describing the changes occurring in the cells of
inflamed connective tissue of the rat. There he gives a good
description of the involution of the fat cells. The process
shows the same phenomena in the involution of the fat cells
in the connective tissue of the living animal after inflammation
as are to be seen in tissue culture. The flattening out of the
cytoplasm, the dividing up of the big fat globule into small
droplets inside the cell (Maximow, plate 3, fig. 9; Erdmann,
text-fig. A) and the transformation of the plasma in a honey-
combed mass (Maximow, Plate 3, fig. 11; Erdmann, fig. 7, left
side, above), are identical processes in both cases. Maximow
believes (’04, p. 119) that some of these cells become fibroblasts.
The present author ventures no opinion on the subject, though a
striking similarity exists between the fibroblasts of Maximow
(text-fig. B) and the cell in figure 7, right side above.
Q2 RHODA ERDMANN
We find after the second day in our cultures: (1) cells of the
fibroblast type; (2) cells of the ‘Riesenzellen’ type; (3) cells of
the cell culture type, after Foot. All three types can originate
from the implanted fat cell.
Besides these progressive changes we must state that many im-
planted fat cells undergo destruction. This is shown by the obser-
vation of the living cells as described on pages 79 to 81. Figure
4, shows such a disintegrating mass of fat cells from an unstained
preparation, and figure 7, shows the mass in a stained prepara-
tion. Here two cells of the honeycombed type are recogniza-
Text fig. B Maximow, 1914, figure 8, plate 3. Involution of a fat cell in an
area of inflammation into a fibroblast.
ble (left side, above), one of which is intact, the other has ex-
pelled the contents of the plasma. Microlymphocytes are gath-
ered around the disintegrating fat masses and the transformed
fat cells. Maximow describes how his polyb asts, cells of the
lymphocyte order, crowd around the fat cells and destroy them by
phagocytosis (page 120). The same phenomenon occurs in the
tissue culture; between the second and the fifth day the destruc-
tion and resorption of the dying fat cells is finished and the tis-
sue culture gradually assumes a different aspect, as will be de-
seribed later.
CHICKEN BONE MARROW IN PLASMA MEDIUM 93
But together with these retrograde processes, easily observed
in the living culture, small parts of the irregularly-shaped, large,
disintegrating fat cells isolate themselves. They become spheri-
eal in shape and begin to wander away from their ‘mother cells.’
They can be recognized by their small nuclei, their coarse glisten-
ing plasma. They are identical with small fat cells. This ‘re-
juvenation’ of the fat cell was only observed when bone marrow
tissue of younger well-fed animals was implanted. Bone marrow
from very young chickens and tissue from old hens seldom re-
juvenate the fat cells, when such are present. In tissue from
older hens the disintegration of the fat cells often obscures the
observation of the other cell types.
THE FATE OF THE MONONUCLEAR BASOPHIL CELLS OF THE BONE
MARROW IN TISSUE CULTURES
When implanted in the plasma medium, the bone-marrow
particle itself appears basophil after preservation with Orth’s
fluid and staining with Giemsa stain. For a long period, up to
14 days, it shows a strong basophilic character. We have shown
how fat cells and their derivatives generally have a strongly
basophil nucleus and often a basophil plasma. Erythrocytes,
erythroblasts, and eosinophil leucocytes, which show a strong
basophily of the nucleus, emigrate or are washed out of the tis-
sue particle and either perish or undergo the changes described.
The eosinophil leucocytes, diminishing the size of their nuclei
and acquiring an acidophil cytoplasm, later form, together with
the erythrocytes, the reddish halo around the implanted particle.
After the first emigration or washing out of the cell types
mentioned, the tissue particle consists almost solely of basophil
cells, which are very young, small, unripe erythroblasts, small
lymphocytes, connective tissue cells of the bone marrow net-
work, and basophil cells of all sizes and forms, the character of
which is not at first recognizable. The thickness of the tissue
particle prevents the closest examination, but these cells have
always ungranulated plasma. In figure 8, a general survey of
these basophil cells is given, as they appear after one hour’s in-
O4 RHODA ERDMANN
cubation in bone marrow of a young nearly fat-less chicken.
Two types besides the erythroblasts with their more or less
pinkish plasma and their wheel-like nuclei are distinguishable—
cells with crude irregular cell plasma, as if it has been torn
They possess small, condensed, highly chromatic nuclei (fig. 8
left side, above), or their cytoplasm has well-rounded contours
and a very big nearly chromatinless nucleus. This type and
its changes will now be described.
In figures 11 to 27, different emigrated cell types of a similar
bone-marrow particle are represented. The particle itself was
twice extracted during an incubation period of 24 hours. The
emigrated cells of each extraction stayed 12 days in the plasma
until they were preserved and stained and later analyzed, so no
new rear guard of eosinophil leucocytes and those mononuclear
basophil cells, the fate of which Foot tried to elucidate, need be
considered. According to this experiment, which was repeated
several times, besides the eosinophil leucocytes the changes of
which (fig. 11 to 19) have been fully treated on page 85, six
different cell types are recognizable after the second extraction.
1. Cells which resemble fat cells (figs. 20 and 21).
2. Cells which, by their nuclear structure but not by their
cell plasma, resemble true connective tissue cells (figs. 22 to 24).
3. Cells which are true connective tissue cells, from the type .
of endothelial cells (fig. 27).
4. Cells which are true connective tissue cells not shown in
figures 20 to 27 but in figure 9, with star-like, fine protoplasmatic
processes and elongated, often cone-like shapes, and a more
mesenchymelike character.
5. Cells which are microlymphocytes (fig. 25 and also fig. 27).
6. Cells which are lymphocytes (fig. 26).
Cell types 3, and 6 are not often found in preparations made
according to the prescribed method. The lymphocyte with its
fine red granules (fig. 26) shows all signs of degeneration. It ap-
pears highly probable that in the plasma clot the normal ripening
out of the large mononuclear lymphocyte began but could not be
fully accomplished owing to the conditions of the culture medium.
The endothelial cell and the elongated connective tissue cells
CHICKEN BONE MARROW IN PLASMA MEDIUM 95
(figs. 27, 9, and 38) have not changed their characters. They
already appear on the first day after incubation, because they
could be observed in bone marrow culture of 24 hours incuba-
tion. The elongated connective tissue cell is highly amoéboid,
and shows in its plasma, on the first days of incubation, fine and
bigger fat droplets, which are coarser when stained with specific
fat stains. Later their plasma looks as if pulverized with small
fat droplets, still later they lose their fat and appear highly
vacuolized. They repeat on a smaller scale the changes of em-
bryonic subcutaneous connective tissue that had been incubated
14 days in a plasma medium. Because these cells appear after
the first day of incubation (the present author has observed them
after but five hours’ incubation) it appears highly improbable
that they originated from the basophil spherical cells in question.
They are cells of the bone marrow network or the vessels of the
bone marrow, which have been torn apart by the cutting of the
bone marrow. They can be also observed in tissue cultures of
true adipose tissue and are distinguished by their rapid division
rate.
In most cultures of connective tissue made by various authors
these cells have been described. Lambert and Hanes (11)
mention the accumulation of fat and the vacuolization of
the cytoplasm in cells of mesenchymal origin. They repre-
sent tumor cells in their publication of 1911, plate 66, figures 4
and 5, of this character. Lambert himself in 1912, on plate 72,
figure 3 and plate 74 figures wandering cells from the chick
spleen. Some of these forms are more related to the connective
tissue cell type in question, some resemble more the cell type
seen in bone marrow cultures when the fat cells have begun the
disintegration. In 1914, plate 44, figure 6, he gives a good proof
of this.
In figure 9, Carrel and Burrows, (’11), represent also fat stor-
ing cells of this type. They are said to be originated from an
adult chicken spleen, while the first author must have seen the
elongated vacuolized type (13, plate 17, figure 16), in culti-
vated connective tissue. Lewis, R. M., and Lewis, H. W., ’11,
show on their figure 20, left side, in a chicken liver culture,
highly vacuolized cells of the same type.
Q6 RHODA ERDMANN
This comparison could be continued but the facts prove already
that among connective tissue cells of the most varied parts of
the chicken body these elongated, finely vacuolized, slender cells
appear with a true connective tissue cell nucleus. They are all
similar to the figures of Foot representing his X cells (ef. Foot
12, plate 22, figures 8, 16, 19). The connective tissue cell rep-
resented by the present writer in figure 9, is taken from a young
chicken and is not of the same size as some of those cells which
Foot shows. When cells, however, were taken from the bone
marrow of a full-grown chicken, they were of the same dimen-
sions as those given by Foot, ’12, plate 22, figure 8.
Also, in the development of embryonic bone marrow tissue of
the chicken, Dantschakoff, ’09, depicts mesenchyme cells (plate 44,
figures 5 and 6) which have a close resemblance to the above men-
tioned cell type (fig. 9). They are identical types, except that
the latter may contain fat, the first are fatless. In this group
must also be included the elongated forms of Foot’s Riesenzellen
which have pointed pseudopods.
To summarize: Though fat containing and often vacuolized
the elongated cells with connection tissue like nuclear structure
which appear in Foot’s figures among his ‘Riesenzellen’ are true
connective tissue cells. There can be no doubt that the granular
lymphocytes, the elongated cells of connective tissue charac-
ter, and the endothelial cells did not originate de novo in the tis-
sue culture.
In studying the cells close to the connective tissue network of
the bone marrow the present writer could only distinguish one
well defined cell type (figs. 36 and 37). Small round cells with
strongly basophil cytoplasm and large, faintly staining nucleus
with two nucleoli are abundant. They are neither microlym-
phocytes nor mononuclear lymphocytes nor erythroblasts. They
differ from the microlymphocytes by their vesicular nuclei, from
the mononuclear lymphocytes by their size and their cytoplasm,
from the erythroblasts by their nearly chromatinless nuclei and
also by their size. In living cells the nuclei of erythroblasts ap-
pear whitish, the nuclei of these cells dark. If these cells,
which migrate from the tissue particle after the leucocytes are
CHICKEN BONE MARROW IN PLASMA MEDIUM 97
washed out by continued changing of the plasma, on the sec-
ond incubation are allowed to develop we find after a fortnight
two different types: figures 20 and 21, and figures 22 to 24.
The cell represented in figure 21 differs from the basophil cells
which had been implanted into the tissue culture (fig. 8, and
figs. 36 and 37) only by its size and by the more chromatic con-
tents of its nucleus. These forms are numerous; they later
contain fat or vacuolize, forming chains, the cells of which are
always to be distinguished by their nuclear structure from the
eosinophil leucocyte. The nucleus has a close resemblance to
that in fat cells; it is vesicular with round bulky, chromatic
contents.
The next group (figs. 22 to 24) have a true connective tissue
cell-like nuclear structure. The nuclei are elongated and fine
threads of chromatin form a true connective tissue nucleus net-
work. The cytoplasm is basophil in most cases, but in cer-
tain parts of the culture and in very old cultures it becomes
acidophil. The basophily or acidophily of cells is no constant
character in tissue cultures. Rous (713, page 183) points out
the changes in acidity of growing cells. The cells themselves
become acid in the culture medium, after having been basophil.
Later they may regain their basophil character. The cells in
question are true phagocytes (fig. 23). They contain fat, blood
corpuscles, dead nuclei, and other disintegrating particles. They
are sometimes polynuclear; as the cell body does not divide they
form also the so-called ‘Riesenzellen’ of Foot. They are more
agile after the first days’ of incubation. In older cultures they
assume round, spherical and oblong shapes, and their enormous
protoplasmatic body divides up. They then form the cell cul-
ture type (fig. 6) the nuclei of which are always vesicular and
not very chromatic.
Therefore, in the group of Foot’s ‘Riesenzellen’ do belong be-
sides the products of the involution of the fat cells and the
implanted elongated connective tissue celltype with its finely
vacuolized plasma, these forms (figs. 22 to 24) in which the
nearly fat-less bone marrow of a young chicken was used. This
gave conclusive proof that the small mononuclear basophil cell
THE AMERICAN JOURNAL OF ANATOMY, VOL. 22, NO. 1
QS RHODA ERDMANN
(figs. 8, 35, 36 and 37) after leaving the bone marrow network,
-an form ‘Riesenzellen’ which by their nuclear structure resemble
connective tissue cells. They later become the cells to which
Foot gave the name ‘“‘cells of the cell culture type.”’ They are
enlarged, fat-storing or vacuolized cells capable of phagocytosis.
The results here presented, i.e., the change of the small vesicu-
lar basophil cell into true phagocytes and later into ‘Riesenzellen’
or cells of the cell culture type—were attained by using the bone-
marrow of a young, fat-less chicken and the washing out of the
undesired cell types, as polymorphonuclear leucocytes. But even
if we use the fatty bone-marrow of a full-grown chicken and con-
trol the daily changes, the same fact is demonstrated. The first
day after incubation (fig. 7) we observe a large number of baso-
phil mononuclear lymphocytes. Three are shown in one micro-
scopic field. Their pale nuclei, often of a lighter blue than the
plasma, the irregular shape of their plasmatic body in which
sometimes a few fine-acidophil granules are visible, and their
large size, make them conspicuous. Examining preparations of
the same series a day later, the lymphocytes are very scarce.
On the fifth day of incubation, when the disintegrated fat has
been disposed of by the phagocytic activity of these basophil
cells, characterized by their close position to the network of the
bone marrow, they are by far the most numerous types in our
tissue cultures. In the following days they grow and divide
rapidly forming ‘Riesenzellen’ which can store fat, become vacu-
olized, and end in rounding off and becoming cells of the cell
culture type, their nuclei with a fine thread-work of chromatin
becoming more like true connective tissue nuclei. They can
even lose their basophily but may always be distinguished by
their nuclear structure from the products of the regressive de-
velopment of the eosinophil leucocyte in tissue cultures.
It might be possible to interpret Foot’s text-figure 5, (page 459,
12) as representing a tissue culture preparation just in such a
stage; because the time for formation of these features is the
same. But then it is not explained why Foot does not describe
the formation of the ‘giant cells’ and cells of ‘cell culture’ type
after 24 hours’ incubation.
CHICKEN BONE MARROW IN PLASMA MEDIUM 99
In the above mentioned preparations the bulk of all cells,
with their fat storing and phagocytic capacities, their vacuolized
cytoplasm have now left the implanted bone marrow particle.
They advance with their fine, pointed, plasmatic pseudopodia to
the outskirts of the plasma clot. Their faintly chromatic nu-
cleus has only two nucleoli. This character is evident in the
youngest cells of that kind which are close to the network of the
bone marrow (figs. 36 and 37) and is also found in ‘Wanderzel-
len’ after Dantschakoff (cf. Dantschakoff, 09, page 133), plate 7,
figures 2 to 5. These ‘Wanderzellen’ which originate from a
mesenchyme or endothelial cell can, according to Dantschakoff,
either be histiotypic or lymphocytic. They form in the em-
bryonal development specific elements of the connective tissue
or the hematopoétic apparatus, according to the conception of the
monophyletic school. In older cultures nearly all basophil cells
have nuclei of true connective tissue cell character, e.1., the chro-
matic granules of the nucleus are connected with fine threads.
They are identical with those nuclei figured in figures 22 to 24.
Not so frequent are types of nuclei figured in figures 20 and 21.
The ‘Wanderzellen’ in the tissue culture lose, in the later days
of their existence, especially in unrenewed tissue cultures, their
fine cytoplasmatic processes but are—by the structure of their
nuclei and their cytoplasm—connective tissue cells of a more
mesenchymelike character. They are transformed to cells of
the cell culture type.
That these cells are descendents of the implanted cells, which
were lying close to the bone marrow, is further proved by the fol-
lowing experiment. After all loose cells in the meshes of the
bone marrow are washed out by repeated changing of the plasma
medium, cells of the type in figures 20 to 24, can be formed.
After three changes of the culture medium, with a period of
two days between, the cells close to the network formed vacuo-
lized cells which could be interpreted in no other way except as
‘Wanderzellen.’ Their nuclei had become nearly chromatinless,
and their plasma acidophil; they sometimes assumed the char-
acter of fat cells, but were generally of the ‘Wanderzellen’ type.
LOO RHODA ERDMANN
No large mononuclear lymphocytes could be seen. It is,
therefore, also evident that a new formation of this cell type,
the mononuclear large lymphocyte of the bone marrow, does not
occur in the tissue culture. The smaller and larger basophil
cells with a vesicular nucleus near the bone marrow network,
and the cells which later leave the network are ‘Wanderzellen,’
a type closely related to the mesenchymal cell. They can be
kept alive for longer periods in renewed culture-medium.
The empty network of the bone marrow, consisting of slender
connective tissue cells, has lost its power of sending new cells
into the surounding plasma clot. The network cells remain liv-
ing for long periods in renewed medium changing only their cyto-
plasma in the same manner as other connective tissue cells do in
plasma culture. It becomes perforated with sieve-like vacuoles
which may store fat.
SUMMARY
The growth of chicken bone marrow in chicken plasma may be
divided into two distinct periods. The first period has a more
regressive character. As process of this first period may be
enumerated:—the degeneration of the erythrocytes and the
nearly full-grown erythoblasts, the ripening of the granulocytes
implanted with the bone marrow into the tissue culture; and the
decay of the latter.
The eosinophil mononuclear or polymorphonuclear leucocytes
after rapid multiplication lose their granules, are flattened out,
and form cell chains of acidophil character which undergo slow
destruction.
The myelocytes moving at first amoéboid-like in the plasma
clot, and behaving like phagocytes, seldom divide, but ripen out
until they assume a large size. Then their plasma vacuolizes
and disappears, leaving only the nuclei.
The microlymphocytes show no signs of multiplying. They
leave the meshes of the bone marrow particle; later lose their
cytoplasm; and finally leave their condensed nuclei in the
culture.
CHICKEN BONE MARROW IN PLASMA MEDIUM 101
The large mononuclear lymphocytes of the type occurring in
the flowing blood, present in great numbers after the first day of
incubation, form now and then fine granules, but undergo no
further development into myelocytes. They lose their nuclear
chromatin, and their plasma becomes honeycombed and finely
vacuolized, and they finally leave as the only trace of their ex-
istence faint shadows in the plasma clot.
The so-called fat cells of the bone marrow flatten out; the
big fat globules divide into smaller droplets; their plasma either
vacuolizes and forms long needle-like projections, or fibroblast-
like cells with a central nucleus and honeycombed plasma. The
first cell type is phagocytic. These cells represent ‘Riesenzel-
len’ in the first period of the tissue culture growth. Not all
cells of this type are transformed into fibroblasts or ‘Riesenzel-
len.’ Some fat cells disintegrate filling the culture medium with
degenerating fat particles. Now and then the nucleus, with a
small amount of cytoplasm separates from the dying ‘fat cell’
and a young ‘rejuvenated’ cell of fat cell character appears. The
so-called fat cells combine the first regressive period of bone
marrow growth with the second of more progressive character.
Some undergo destruction, some survive, later assuming Foot’s
cell culture type.
From the first day of incubation, connective tissue cells of
elongated shape with very fine pointed projections migrate into
the plasma clot. They store fine droplets of fat and partially
vacuolize. They are also found in the second period of growth
in the tissue culture.
The second period begins with the loosening up of the cells
around the network of the bone marrow; the smaller, or larger
basophil cells, with vesicular nucleus migrate into the surround-
ing plasma and the network sends new cells into the plasma clot
till it is utterly devoid of cell forms. These cells represent an
intermediate type between the ‘histiotype Wanderzellen’ (Dant-
schakoff, 09) and the embryonic mesenchyme cell. They do not
resemble in all details the large nononuclear lymphocyte of the
blood. They move into the surrounding plama, send out pene-
trating needle- and bristle-like projections; divide into phago-
102 RHODA ERDMANN
cytes; store fat; lose their projections and partially vacuolize, as-
suming the form of the ‘‘cell culture type.”
The network of the bone marrow, having lost its cells, and no
longer able to send out emigrating cells, consists of slender con-
nective tissue cells. These show a remarkable paucity of
chromatin, are strongly acidophil, and possess sieve-like vacu-
oles of the finest type.
The ‘Riesenzellen’ of Foot comprehend several cell types:
1. Transformed fat cells and elongated, vacuolized connective
tissue cells.
2. Newly emigrated basophil cells of the bone marrow
network, which are related to the “histiotype Wanderzelle” of
Dantschakoff.
3. Some few myelocytes and flattened out eosinophil mono-
or poly-morphonuclear leucocytes.
These two phenomena, the dying of the cell forms which are
not adapted to the continued growth in tissue culture, and the
adapting of a new character by those cells which are capable of
living longer periods in the plasma medium, often overlaps.
They appear more sharply separated in cultures of almost fat-
less bone marrow, where few ‘Riesenzellen’ appear in the first
days of incubation. From the third to the fifth day, when the
loosening of the bone marrow network and its content has begun,
they become numerous. The duration of these periods may be
stated as follows: The first period lasts from the first to the third
day; the second period from the third day to the death of the
culture. The surviving cells of the cell culture type (Foot) are
modified fat cells and newly formed wandering cells of the mes-
enchymelike type. After fourteen days’ cultivation, they are,
except the elongated connective tissue cells the only living cells.
They belong to the connective tissue cell type and may, when
the medium is renewed, grow indefinitely.
DISCUSSION AND CONCLUSIONS
As one of the first results of our analytic study, let us discuss
the fact that the so-called X or ‘Riesenzellen’ of Foot represent
several different cell types. The myelocytes and larger eosino-
phil leucocytes acquire, as shown, good dimensions in the tissue
CHICKEN BONE MARROW IN PLASMA MEDIUM 103
culture of bone marrow. ‘The myelocytes, capable of amoéboid
moving, form few ‘Riesenzellen.’ They can easily be omitted
in the following discussion, as they are always distinguished by
their characteristic nuclei and the blunt form of their projections,
when stained and preserved. They are just as unmistakable
when living. The large mononuclear or polymorphonuclear
eosinophil leucocytes only need be considered, as X or ‘Riesen-
zellen’ when they have flattened out and formed rays of cells.
Then they are surrounded by the projections of the transformed
fat cells or cell types of the ‘histiotype Wanderzellen’ order.
Both cell types are true phagocytes, thus forming, chiefly in the
first days after incubation, cell masses of X or ‘Riesenzellen’ of
combined characters. The whole combination may even seem,
judged only by its acidophil staining, to be from a different
origin. But the daily observations reveal the facts of their de-
velopment. It is questionable if any necessity exists for giving
new names, as Foot did in 1912 and 1913, for the X cells ‘Riesen-
zellen’ and later forms. ‘They are either transformed fat cells,
or mesenchymelike wandering cells which have left their custom-
ary place and which assume in later life in tissue culture the
characters of connective tissue.
The name ‘Riesenzellen’ or true giant cells has already been
used for cells of the type represented in figure 10. This multi-
nuclear cell was seen in a tissue culture of bone marrow from a
two-months old chicken, and resembles in every particular the
true giant cells figured and described by many authors.
To call the questioned basophil cells ‘X cells’ when their ori-
gin is known would be a contradiction. They are either ‘fat
cells’ or mesenchymelike cells, and both types are transformed
from their original type by our cultivation method. The present
author would propose calling the latter simply wandering
mesenchymelike cells, and the fat cells, transformed fat cells.
Their close relationship to the mesenchymal cell type is again
proved by their physiological behavior in tissue culture, so closely
identical with that of the wandering mesenchymal type. It
even became evident that some ‘fat cells’ may assume the
character of fibroblasts when they are not transformed into
104 RHODA ERDMANN
highly vacuolized or fat-storing cells of mesenchymal character
with projections at first needle-like and later of a rounded or
elongated shape. This twofold manner of development of the
bone marrow fat cells is important, as it might probably be the
result of a non-uniform origin.
In judging the transformations of cell types of mesenchymal
origin in tissue culture, we already have established certain
facts as a basis of comparison. The mesenchymal cells always
erow more rapidly than any other known tissue; they have the
ability to store fat; they can vacuolize and can emigrate out of
the tissue clot. They can endure this highly artificial method of
breeding indefinitely. The bone marrow particle, with its loose
meshes, exhibits many ‘Wundflichen’ which are incited into new
growth by the stimulus given by the cutting of the tissue. By
repeatedly renewing the culture medium and transplantin — the
tissue particle, we stimulate the growth again and again, until
we have exhausted the power of the network to send newly
formed mesenchymelike cells into the plasma, and only a fine
thread-like network with a few oblong, small nuclei remains.
The pliability of the mesenchymal cell and its ability to undergo
transformations is known in embryonic life and is here demon-
strated in tissue culture life.
Two subjects of importance have not been touched. Can
these wandering mesenchymal cells form fibrils, and have they
any relation to the formation of the different elements of the
bone marrow? Throughout the whole description of the cell
transformations in tissue culture, the writer has avoided Foot’s
conclusion of 1912, namely, since his X cells form fibrils, they
must be of the mesenchymal type. The tissue particle of bone
marrow has a fibril-forming connective tissue of its own. When,
now and then, fibril-forming cells have been seen (as has been
the experience of the writer), they may either originate from
cells already implanted in the tissue culture, with the bone-
marrow particle, or the imbedded fibrils (Foot 712, plate 22, fig.
15) may represent fibrils or fibers formed by the fibrin-contain-
ing plasma of the culture medium (Baitsell 714, 715). Foot
maintains that his X cells form fibrils but he does not prove it.
CHICKEN BONE MARROW IN PLASMA MEDIUM 105
Proof could only be obtained by cultivating isolated cells of a
certain known type in a medium which does not contain fibrin
as the plasma does. This has never been done and still re-
mains a subject for future investigation.
The author agrees with Foot’s view of 1912, that X cells, or
the conspicuous cells in tissue cultures of bone marrow, are of
mesenchymal type, not because they contain fibrils, but be-
cause their origin could be traced and their cytological changes
could be recorded. Foot’s statement of 1913, must be refuted:
that the transformation passed through the stages of small mi-
crolymphocyte, macrolymphocytes, large mononuclear forms,
myelocytes, polymorphonuclear eosinophil leucocytes, X cells,
cell culture type, omitting one or the other forms of this stage,
so that directly a lymphocytic origin is considered. It was never
observed that true microlymphocytes were transformed into
macrolymphocytes in the tissue culture. The basophil cell with
vesicular nucleus, pale cytoplasm of various sizes in the net-
work of bone marrow, assumed the cell culture type, after wander-
ing into the cytoplasm, forming point-like projections, dis-
playing the capability of phagocytosis, storing fat, and being
vacuolized. There was no stage observed in this transformation
which resembled the large mononuclear lymphocyte or the ‘lym-
phocytoid Wanderzelle’ of Dantschakoff, though this type could
be easily observed in chicken bone marrow when the bird had
eyanolophia. The close resemblance with Dantschakoff’s ‘his-
tiotype Wanderzelle’—cells which form (09, page 177), after
some changes, the ‘ruhenden’ wandering cells of the connective
tissue—could, only be discovered when the basophil forms left
the net-work and began to emigrate.
It appears highly plausible that in tissue culture the indifferent
mesenchymelike cell in the bone marrow network does not show
its supposed duality, either to form the known elements of the
connective tissue or according to the views of the monophyletic
school, the different elements of the hemato- and granulopoésis.
In a medium, where circulation has ceased, where no oxygen
renovation takes place, the potency to form the lymphocytic
elements of bone marrow may not be strong enough to over-
106 RHODA ERDMANN
come the potency to form fat cells, fibroblast and ‘histiotype’
wandering cells. Therefore the present series of experiments
does not prove anything concerning the views of the mono- or
duophyletic schools, of the formation of blood and lymph in the
bone marrow. Here renewed experiments should be made, the
different cell types after emigration should be isolated and sub-
mitted to conditions reproducing either the condition of the
blood or of the lymph. Only with still more refined methods
would it seem possible to elucidate, outside the body, the com-
plicated process of blood and lymph formation.
But this series of experiments proves that the latent qualities
of the basophil mononuclear cells in the meshes of the bone
marrow can arise de novo in the adult animal, because their
wandering phagocytic, fat-storing character has been made evi-
dent. This fact ought to be considered in dealing with the ap-
pearance of these, and related cell types in the blood and lymph
during diseases.
BIBLIOGRAPHY
Ba1TseELL, G. A. 1915 The origin and structure of fibrous tissue which appears
in living cultures of adult frog tissues. Jour. of Exper. Medicine,
vol. 21, p. 455-479.
1916 The origin and structure of fibrous tissue formed in wound
healing. Jour. of Exper. Medicine, vol. 23, p. 739-756.
Bez, E. T. 1909 On the histogeneses of the adipose tissue of the ox. Am.
Jour. Anat., vol. 9, p. 412-438.
Burrows, M. T. 1910 The cultivation of tissues of the chick embryo outside
the body. Jour. of the Amer. Med. Assoc., vol. 55, p. 2057.
1911 The growth of tissues of the chick embryo outside the animal
body, with special reference to the nervous system. Jour. Exp. Zodl.,
vol. 10, p. 63-83.
CarRREL, A. 1913 Contributions to the study of the mechanism of the growth
of connective tissue. Jour. of Exp. Med., vol. 18, p. 287-299.
CaRREL, A. AND Burrows, M. T. 1913 Cultivation of tissues in vitro and its
technique. Jour. of Exper. Med., vol. 13, p. 387-397.
DantscHakorr, W. 1909 Untersuchungen iiber die Entwicklung von Blut und
Bindegewebe bei Végeln. Das lockere Bindegewebe des Hiihnchens
im fétalen Leben. Arch. f. mik. Anat, Bd. 73. p. 117-182.
1909 Uber die Entwickelung des Knochenmarks bei den Vogeln und
dessen Verinderungen bei Blutentziehungen und Ernihrungsst6-
rungen. Arch. f. mikr. Anat., Bd. 74, p. 855-929.
CHICKEN BONE MARROW IN PLASMA MEDIUM 107
Emmet, V. E. 1914 Concerning certain cytological characteristics of the
erythroblasts in the pig embryo and the origin of non nucleated
erythrocytes by a process of protoplasmic condition. Am. Jour.
Anat, vol. 16).p. 127.
Foot, N. C. 1912 Uber das Wachstum von Knochenmark in vitro. Ex-
perimenteller Beitrag zur Entstehung des Fettgewebes. Beitr. z.
path. Anat. z. allg. Pathologie Bd. 53, p. 446-477.
1913. The Growth of chicken bone marrow in vitro and its bearing
on hematogenesis in adult life, Jour. of Exper. Med., vol. 17, pp. 43-60.
Harrison, R. G. 1907 Observation on the living developing nerve fibre.
Proc. Soc. Exp. Biol. and Med., vol. 4, p. 140-46.
1910 The outgrowth of the nerve fiber as a mode of protoplasmic
movement. Jour. Exp. Zodél., vol. 9, p. 787-848.
Juspa, V. 1913-1914 Uber den Entstehungsmechanismus der Cabotschen
K6érper und ihre diagnostische Bedeutung bei den experimentellen
Aniimien oder den schweren Aniimien des Menschen. Folia Haemat-
ologica, Bd. 17, p. 429-441.
Lampert, R. A. 1912 The production of foreign body giant cells in vitro.
Jour. of Exper. Med., vol. 15, p. 510-516.
1914 The effect of dilution of plasma medium on the growth and fat
accumulation of cells in tissue cultures. Jour. of Exper. Med., vol.
19, p. 398-405,
LAMBERT, R. A. anp Hangs, F. M. 1911 Growth of sarcoma and carcinoma
cultivated in vitro. Jour. of Exper. Med., vol. 13, p. 495-504.
Lewis Reep, M. anp Lewis, H. W. 1911 Cultivation of chick embryo tissues.
Anat. Rec., vol. 5, p. 277-288.
Maximow, A. 1904 Uber entziindliche Bindegewebsneubildung bei der.
weissen Ratte und die dabei auftretenden Verinderungen der Mast-
zellen und der Fettzellen. Beitr. zur path. Anat. und zur. allg. Path-
ologie. Bd. 35, p. 93-127.
1909 Untersuchungen iiber Blut und Bindegewebe. Die friihesten
Entwickelungsstadien in Blut und Bindegewebszellen beim Siugetier
embryo, bis zum Anfang der Blutbildung in dem Leben. Arch. f.
mikr. Anat. Bd. 73, p. 380-444.
1910-1911 Untersuchungen iiber Blut und Bindegewebe. III. Die
embryonale Histiogenese des Knochenmarkes der Siugetiere. Arch.
f. mikr. Anat., Bd. 76, p. 1-114.
Oppet, A. 1912 Causal morphologische Zellenstudien. V. Mitteilung. Die
active Epithelbewegung ein Factor beim Gestaltungs und Erhaltungs
geschehen. Arch. f. Entw., Bd. 35 p. 371-456.
1912 Uber die Kultur von Siugetiergeweben ausserhalb des Orga-
nismus. Anat. Anz., Bd. p. 464-468.
1912 Kausal-morphologische Zellenstudien. IV. Mitteilung. Die
Explantation von Siugetiergeweben ein der Regulation von seiten
des Organismus nicht unterworfenes Gestaltungsgeschehen. Arch.
f. Entw., Bd. 34, S. 132-167.
Rous, P. 1913 Growth of tissue in acid media. Jour. of Exper. Med., vol.
18, p. 183-186.
108 RHODA ERDMANN
Watton, A. J. 1911 Variation in the growth of adult mammalian tissue in
autogenous and homogenous plasma. Proc. R. 8. L., B., vol. 87,
p. 452-61.
1914 The effect of various tissue extracts upon the growth of adult
mammalia cells in vitro. Journ. of Exper. Med., vol. 20. p. 554-573.
EXPLANATION OF PLATES
The drawings were made from total preparations, with Abbe camera lucida,
Zeiss homogeneous immersion 2 mm. and compensating ocular 12, with drawing
board level with stage of microscope. Magnification about 1500 diameters.
PLATE 1
EXPLANATION OF FIGURES
The bone marrow used for the preparations shown in figures 1 to 6 was taken
from a well fed, full grown chicken containing a large amount of fat. It was
incubated at a temperature of 38°C. in the chicken plasma medium.
1 The first cells emigrating from the particle into the plasma. Bone marrow
one hour in plasma, January 3, 1916, 10 a.m. to 11 a.m. Two mononuclear
eosinophil leucocytes, one lymphocyte, and one normoblast are visible.
2 Cells which have left the implanted bone marrow particle after twenty-
four hours and emigrated into the plasma. January 3 to January 4, 1916. Mon-
onuclear and polynuclear eosinophil leucocytes with rod-shaped granules and
large granulocytes with rounded, highly refractile granules are visible. Two
fat cells at the right and left side of the preparation have divided up their big
fat globule into small fat droplets (compare plate 6). In the middle a large non-
granular lymphocyte is to be seen.
3 Cells which have left the implanted bone marrow particle and have ad-
vanced to the border of the plasma clot after forty-eight hours’ incubation.
January 3 to January 6, 1916. One large ‘Riesenzelle’ and a small granulocyte
with highly refractile granules are visible together with one small lymphocyte
with vesicular nucleus. Red blood corpuscles with or without nuclei are present.
One red blood corpuscle extrudes its nucleus.
6 Cells which have stayed two hundred and sixteen hours in the plasma
medium December 25, 1915 to January 3, 1916. Cell culture types.
PLATE 1
HICKEN BONE MARROW IN PLASMA MEDIUM
RHODA ERDMANN
PLATE 2
EXPLANATION OF FIGURES
4 Cells near the implanted tissue particle after seventy-two hours’ incuba-
tion. January 3 to January 6, 1916. Extrusion of fat droplets and breaking up
of the ‘Riesenzellen.’
5 Cells on the outskirts of the surrounding plasma after ninety-six hours’
incubation. Disintegration of fat cells. Note the very small leucocyte.
110
ICKEN BONE MARROW IN PLASMA MEDIUM PLATE 2
RHODA ERDMANN
PLATE 3
EXPLANATION OF FIGURES
7 Total preparation: Bone marrow of a full-grown, well-fed chicken after
thirty hours’ incubation at 38°C. in the plasma medium. January 3 to January
4, 1916. Orth’s fluid, Giemsa stain. (Compare for explanation pages 89 and
98-100.) Actual field represented.
SF 4,
PLATE 3
113
RHODA ERDMANN
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B
CKEN BONE MARROW IN PLASMA MEDIUM
PLATE 4
EXPLANATION OF FIGURES
8 Total preparation: Bone marrow of a chicken not yet full grown, with
a small amount of fat, after ninety minutes’ incubation at 38°C. in the plasma
medium. June 7, 1916. Orth’s fluid, Giemsa stain. Small eosinophil leu-
cocytes and many basophil cells with vesicular nuclei are present.
9 Total preparation: Bone marrow of a full grown, well fed chicken, after
twenty-four hours’ incubation at 38°C. in the plasma medium. December 14
to December 15. Orth’s fluid, hematoxylin, eosin stain. The slender vacuolized
cell with its nucleus of connective tissue cell structure is already visible after
this short incubation period.
114
PLATE 4
ta
PLATE 5
EXPLANATION OF FIGURES
10 Giant cell from the bone marrow of a young, but full grown, well fed
chicken, after one day’s incubation; to represent the type which is generally
named giant cell and is not identical with Foot’s ‘Riesenzelle.’
11 to 19 White bone marrow of a young, nearly fatless chicken in tissue
culture at 38°C. After one hour’s incubation the tissue particle was extracted
and the emigrated cells were allowed to develop further. February 11 to Feb-
ruary 25, 1916. A detailed description of the changes of the eosinophil leuco-
cytes is given on page $2-S4.
20 to 27. The same bone marrow particle after having been freed from its
eosinophil leucocytes by the above described process was implanted for one
day again in a plasma medium and extracted again. The emigrated cells were
allowed to develop from February 12 to February 25, 1916. Figures 20 and 21
represent a cell type more related to fat cells, figures 22 to 24 a type more re-
lated to connective tissue cells, figures 25 to 27 show known cell types which have
not changed their character in the tissue culture. Note figure 24: a so-called
form of the cell culture type. All cells on plate 5 are conserved in Orth’s fluid
and stained with Giemsa stain.
116
PLATE 5
CHICKEN BONE MARROW IN PLASMA MEDIUM
RHODA ERDMANN
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117
PLATE 6
EXPLANATION OF FIGURES
28 to 32. Involution of the so-called fat cells of the bone marrow to ‘Riesen-
zellen’ in the plasma medium. White bone-marrow of a younger well-fed, full-
grown chicken in tissue culture from November 30 to December 1, 1915. Con-
servation: Formol. Osmium, Safranin stain.
118
CHICKEN BONE MARROW IN PLASMA MEDIUM PLATE 6
RHODA ERDMANN
PLATE 7
EXPLANATION OF FIGURES
33 and 34 White bone marrow from a younger full-grown, well-fed chicken
in tissue culture at 38°C. from February 29 to March 1, 1916. Foot’s ‘Riesen-
zellen’ already present after one day’s incubation.
35, 36 and 37 An identical piece of bone-marrow, as described above, was ex-
tracted after three hours and transplanted in a new culture medium. The next
morning, again extracted and transferred in a new medium. After eight hours
the preparation was conserved and the cells nearest to the network studied.
A cell, 35, of this preparation having migrated from the network, showing
phagocytosis.
38 A cell of the network which begins to become disconnected.
39 to 42. White bone marrow from a full-grown chicken in tissue culture from
February 22 to March 2, 1916, at 38°C. Regressive changes of cells of the large
mononuclear type or the myeolocytic type.
The cells figured on figures 33 to 38 were conserved with Orth’s fluid, those on
figures 38 to 42 with Schaudinn Sublimat Alcohol and stained with Giemsa
stain.
120
CHICKEN BONE MARROW IN PLASMA MEDIUM PLATE 7
RHODA ERDMANN
121
PLATE 8
EXPLANATION OF FIGURES
43. Emigrated cells after three hours incubation (mono- and poly-nuclear
eosinophil leucocytes.
44 Emigrated cells after 24 hours incubation (mononuclear basophil cells)
after the culture medium has been once changed after three hours.
Compare page 93-100 for detailed description.
CHICKEN BONE MARROW IN PLASMA MEDIUM PLATE 8
fay ae
‘ Ie ui is % “ J
sees ww
&
RHODA ERDMANN
PLATE 9
EXPLANATION OF FIGURES
45 Involution of the fat cells after 24 hours incubation near to the implanted
bone marrow particle.
46 Involution of the fat cells after 24 hours incubation. Cells near the
periphery of the plasma clot. Compare figures 33 and 34, plate 7, from the same
series of experiments.
124
CHICKEN BONE MARROW IN PLASMA MEDIUM PLATE 9
RHODA ERDMANN
THE RELATIONSHIPS AND HISTOGENESIS OF THY-
MUS-LIKE STRUCTURES IN AMMOCOETES!
IVAN E. WALLIN
Department of Anatomy and Biology, Marquette University Medical School
THREE TEXT FIGURES AND FOUR PLATES
CONTENTS
DEE CLITC LOU Spee eee ace Rhee Oh esi Sle lee aw) «eS ci ee Otc ra 127
ThTEA@UCOT SG Ti a a A Ta nL eres So. £5, S50, hofoNNa acho eae 129
WMieieriatlwand: MethOUSs 2 fas ceken ieee oh < oe <A ape chats Rename Mee ere ores heck 131
Comparative anatomy of the Ammocoete pharynx...............---++-----: 132
Organogenesis of the pharynx in the Ammocoetes.............-.++-+-+-+-->- 137
TRIPS; HOyUCSTEVEIS) TENN Aone alk alts meee as eae Aretha SI rt OP ol5 ond 6 Bis’o ttc, Om a 143
Early development of the. pharyngeal wall in Petromyzon marinus uni-
Color (lame ita wall eri: Yarns Aa.) o.oo ce atensls aes. ne eM RIC a ro oi hon nets 143
Dyas) olakehmanererell ly 0} EEC C0Y6 (=) eet eee EI), cools 8 even reoe ie 146
Development, of, lymphocytes: 6.6) 5542.) oh 2 eee os eel 152
Histogenetic comparisons between cells arising from placodes and -
feyzi OCW LES ss incre ase aS ests ste ooo 1% oo, sae eR entrees ends ore 154
‘DiS(CHS SC tae ts Bee ae a oe Oana ot Glo olds eens 6 155
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“Exile1Ficcytarn 26) dn alee Svs ear eae aan carpe ee PPP ERP ces) C Crd 5 chai eno iea Lae Oe 158
INTRODUCTION
The question of the source and mode of development of the
component structures of the thymus is one of the most difficult
problems in anatomy. Although a vast literature has accumu-
lated during the last fifty years some of the most fundamental
phases of the problem still remain unsolved.
The thymus has been described in every group of vertebrate
animals from the elasmobranchs up to and including man. The
involvement of gill pouches in the formation of the gland has
been established in almost all of the investigated forms. There
1 This thesis has been accepted by the Graduate School of New York Univer-
sity, in partial fulfillment of the requirements for the degree of Doctor of Science.
127
128 IVAN E. WALLIN
is still disagreement on the purely epithelial origin of the reticu-
lum and Hassal’s corpuscles, and the cardinal problem, the source
and nature of the development of the small thymus cells, has not
been definitely settled up to the present time. Three fundamen-
tally different views, each with its coterie of supporters, are held
regarding the source of these cells. A large number of investi-
gators believe that the small thymus cells are true lymphocytes
which are formed from the epithelium by a process of trans-
formation. An equally large number believe that these cells
represent true lymphocytes which have wandered into the epi-
thelial anlage from the mesoderm. <A remaining smaller group
of investigators believe that the small thymus cells have an
epithelial origin and are different from true lymphocytes.
Even in the most primitive animals in which the thymus has
been established, the elasmobranchs, the formation of the small
thymus cells does not occur until mesodermal tissue is present
in the epithelial anlage. The source of a new type of cell which
forms in a mixed tissue would not be difficult to determine if the
two tissues entering into the formation had different morpho-
logical characters and retained them. The methods employed
up to the present time have not shown sufficient morphological
differences in the mesodermal and endodermal cells present in
the thymus anlage to establish the source of the small thymus
cells.
The sudden appearance of the thymus as a well defined struc-
ture in the elasmobranchs, together with the probability of find-
ing a solution to the question of the source of the small thymus
cells, has stimulated a number of investigators to search for a
homologous structure in the more primitive types of chordate
animals. While the search has been a fruitless one in the asci-
dians and amphioxus, various structures have been described
for a thymus in the cyclostomes. The evidence offered in these
descriptions has not been sufficient to establish the organ in this
group of animals. The failure to find the thymus or its homo-
logue in the cyclostomes especially in the Petromyzontes, may
be attributed largely to the peculiar nature of the branchial
region in this primitive group of animals.
THYMUS-LIKE STRUCTURES IN AMMOCOETES 129
The bearing on the interpretation of thymus histogenesis in
higher animals suggested by the development of the organ in a
primitive type, led the author to undertake a systematic study of
the branchial region of, the petromyzon larva. The time and
work which have been given to this study have, I believe, been
amply repaid in the results obtained. Thymus-like placodes
have not only been located in the position which makes them
homologous with the thymus placodes of the elasmobranchs,
but the placodes have also been found in a more primitive con-
dition than they have been shown to exist in any other animal. °
LITERATURE
The search for a thymus in the most primitive chordate ani-
mals has been undertaken by a number of investigators Up to
the present time the organ has not been established in any of
these lower forms Willey (94) suggests that the tongue-bars
occurring in the gill-slits of amphioxus represents the thymus
gland. The position of these structures is apparently the only
basis for this suggestion. Their gelatinous structure, however,
would offset any argument that they were homologous with the
thymus placodes of fishes. Stannius (’84) credits the discovery
of the thymus in the myxinoids to Johannes Miiller. Later
investigators, however, have been unable to verify this dis-
covery. Stockard (’07) in his study of the thyreoid in Bdello-
stoma Stouti was unable to find a thymus in this form. M.
Schultze (56) described a tortuous sac in the ventral wall of
the branchial cavity ‘of Petromyzon planeri which he thought
represented’ a thymus. Schneider (’79) showed that a part of
this structure disappears in the development of the animal while
the remaining part changes into a group of follicles which repre-
sent the thyreoid.
Schaffer (94) described structures in the lateral branchial
wall of a 51 mm. larva of Petromyzon planeri, which he thought
represented thymus anlagen. He found in all twenty-eight
anlagen, seven pairs on each side which consisted of ventral and
dorsal portions. These anlagen were connected with the epithe-
hum of the branchial vestibules.
THE AMERICAN JOURNAL OF ANATOMY, VOL. 22, No. 1
130 IVAN E. WALLIN
The minute structure of these buds is summed up in the
following:
Was den feineren Bau dieser Knospen anlangt, so gestattet mir die
mangelhafte histologische Conservierung (Alkohol) vorléufig nur
folgende Bermerkungen zu’ machen: Von der kapsel dringen feine
Bindegewebsbilkchen in das Innere ein, welche ein sparliches, reticu- .
lumartiges Stutzgeriist fiir die zelligen Elemente bilden. Diese selbst
sind kleine Rundzellen von lymphoiden Aussehen, kaum wahrnehm-
barem Protoplasma, stark fairbbarem Kern und Kerngeriist. Zwischen
denselben finden sich ausserdem gréssere, blasse Kerne mit deutlicher
Kernmembran, unc Kernk6érperchen, welche dem Stiitzgewebe anzuge-
hoéren scheinen und rothe Blutkorperchen, von denen ich nicht sagen
kann, ob sie frei zwischen den lymphoiden Zellen liegen oder einge-
schlossen in Capillaren.
Die lymphoiden Zellen sind wahrscheinlich Abkémmlinge des Kie-
menepithels, wie ihr director Ubergang in das letztere vermuten lisst.
In a subsequent paper Schaffer (’06) withdrew his previous
interpretation and said that he did not believe these structures
represent thymus anlagen.
Giacomini (’00, 1 and 2) believed that ‘‘the lymphoid organ
in the basalar region of the gill lamellae (in ammocoetes) might
fulfill an analogous function to the thymus in the-fishes.”’
Castellaneta ('13) describes the structures which Schaffer
found, but insists that these structures correspond to lymphoid
organs in general and suggests the name ‘lymphoid formations’
for them.
He further calls attention to the fact that on the one side
these lymphoid formations are in contact with the peribranchial
vessels and on the other with the epithelium of the branchial
sac. He does not consider these structures as thymus anlagen
insofar that there is not a reciprocal penetration of epithelial
and lymphatic elements which should occur in a thymus. Cas-
tellaneta calls attention to the abundance of lymphoid cells in
the general branchial region. He suggests that these special
lymphoid accumulations of Schaffer may represent a primitive
condition of the thymus in which the epithelium participates
only to the extent of attracting the lymphoid cells.
These lymphocyte accumulations do not occur in the part of
the branchial cavity which would make them homologous with
THYMUS-LIKE STRUCTURES IN AMMOCOETES 131
the thymus placodes in the fishes. While lymphocytes are present
in these situations the evidence brought out in connection with
them is not sufficient to establish their origin or the cause of their
presence in these places.
A contribution on the ganoid thymus (Lepisosteus, Amia)
has been submitted by Ankarsvard and Hammar (13). They
found the organ a purely endodermal, unsegmented structure in
a medial position in the dorso-caudal part of the epibranchial
region. ‘‘It nevertheless has a segmented origin and the epi-
branchial unsegmented thymus structure représents a secondary
alteration from the branchial segments.’ In the older develop-
mental stages there is a rich infiltration of lymphocytes into the
sub-thymic and perivascular connective tissue which stands
out in striking contrast to the conditions in an earlier stage. The
authors discuss the question whether this condition represents an
immigration into the thymus or an emigration from it They
believe that the cells have migrated from the placode and repre-
sent the beginning of an accidental involution. A lobulization
of the organ does not occur. In the adult Lepisosteus the thymus
is strongly involuted.
The nature of the thymus in the ganoids as described by
Ankarsvird and Hammar is so suggestive of the conditions I
have found in the ammocoetes that it appears to me to repre-
sent but a very small advance beyond a primitive form in the
phylogenetic development of the organ. The origin of the
lymphocytes which were supposed to originally migrate into
the epithelial anlage in the Lepisosteus does not appear to have
been especially determined by the authors.
‘ MATERIAL AND METHODS
The material which is the basis for this work was gener-
ously supplied to me by Prof. Simon H. Gage. It consists of a
series of specimens ranging from the segmentation sphere up to
and including a transforming larva and the adult. These speci-
mens undoubtedly represent two species, Petromyzon marinus
unicolor and Lampetra wilderi (the lake and brook lamprey
of central New York).
132 IVAN E. WALLIN
A number of the 5 mm. specimens in my collection were
kindly given to me by Prof. C. R. Stockard. They were collected
in Naples.
I wish to take this opportunity to express my thanks and
appreciation to Professor Gage and Professor Stockard for this
valuable material.
The specimens were fixed in various fixing fluids: Zenker,
formol; Gilson’s, Bouin’s, picro-acetic, corrosive-absolute alco-
hol. After being imbedded in paraffin, transverse and frontal
sections were cut from 4 micra to 15 micra in thickness. The
sections were stained by various staining methods; methylene
blue and eosin, Weigert’s haematoxylin and eosin. Giemsa’s
eosin-azur, and haematoxylin (Delafield’s) and eosin. The best
differentiation was obtained by the use of the ordinary haema-
toxylin and eosin method.
A paraffined blotting paper model? of a part of the branchial
region of a petromyzon larva prepared by Mr. Warburton was
used in this study. A clay model of a part of the branchial
region was also prepared to facilitate the study of the arrangement
of the ciliated bands in the pharynx.
COMPARATIVE ANATOMY OF THE AMMOCOETE PHARYNX
The phylogenetic position of the lamprey is still a matter of
speculation. Various hypothesis have been advanced in regard
to its position. Some place this animal between the amphioxus
and the elasmobranchs, others claim that it represents a degen-
2 A description of the method of reconstruction referred to above may be of
interest to workers. This method is a modification of the late Mrs. Gage’s
blotting paper method. Sheets of blotting paper are dipped in melted paraffin
and dried. The drawings are transferred to the paraffined paper by the usual
methods when wax plates are used. The cutting is also done in the same way,
the knife used, however, must have a thin but strong blade. In stacking the
sections bank pins were used to hold the sections together. Small screws were
also used occasionally to give firmness. When the stacking has been completed
the sections may be smoothed down by means of any rounded instrument. A
hot iron may also be used to cement the sections together. To give the best
stability the complete model may be immersed in hot paraffin a few minutes.
Models made in this way have a great firmness and are admirably efficient for
class room use where a great deal of handling is necessary.
THYMUS-LIKE STRUCTURES IN AMMOCOETES 130
erate type. However, a comparative study of the branchial
region of the lamprey larva with the same region in ascidians and
amphioxus on the one hand, and with the elasmobranchs on the
other, suggests that the branchial region of the lamprey larva
represents a transitional stage between the amphioxus and the
elasmobranch types.
A few comparisons between the pharyngeal region of the
ammocoete and lower and higher forms may be found in the
literature. Dohrn (’84, ’85) discussed the homology of the thy-
reold of ammocoetes with the endostyle of ascidians and the
hypobranchial ridge in amphioxus and the cireumoral ciliated
ring in the ammocoetes with that of the ascidians. Cunning-
ham (’87) verifies the homologies Dohrn pointed out. Shipley
(87) calls attention to the homology of the dorsal ciliated ridge
in ammocoetes and the dorsal lamellae of ascidians and the
epipharyngeal groove of amphioxus.
The following considerations are based on my studies and
include besides the homologies just quoted a comparison of the
gills in these primitive animals:
The large branchial cavity with its medial gill arches of the
lamprey larva (text fig. 1) is very suggestive of the conditions
in the ascidians and amphioxus. In the ascidians there is a
central pharynx surrounded by a peribranchial cavity. The
two cavities communicate by means of numerous small pores,
the stigmata. It is an unsettled problem whether the peri-
branchial cavity is derived from ectoderm or endoderm. In
amphioxus there is a central pharynx which is partially sur-
rounded by an atrium (peribranchial cavity). In this form the
two cavities communicate by means of definite gill slits. The
atrium of amphioxus is developed from ectoderm. In both forms
there is a ventral endostyle and a structure homologous with the
epipharyngeal ridge. The branchial cavity of the ammocoetes
corresponds to a fusion of the two separate cavities in the asci-
dians and amphioxus. The primitive characters of these sepa-
rate cavities, however, are still present. The central portion,
that is the part bounded laterally by the gill arches (fig. 1,
a.p.), corresponds to the pharynx of the ascidians and amphioxus.
epr
c.e,
!)
IVAN E. WALLIN
THYMUS-LIKE STRUCTURES IN AMMOCOETES 135
It differs from the conditions in amphioxus in that the gill
clefts are very much wider. It is probable that the ammocoete
gill cleft represents the fusion of two or more gill clefts of am-
phioxus. There is an indication of such a fusion in the for-
mation of the tongue-bar or secondary gill bar of amphioxus.
The larger respiratory part of the ammocoete pharynx (text
fig. 1, rp.) corresponds to the peribranchial cavity of ascidians
and amphioxus. The entire branchial cavity of the petromyzon
larva is entodermal in origin. The ammocoete thus represents
a phylogenetic stage in which the respiratory cavity, originaliy
of ectodermal origin, is derived from the endoderm as it is in
most higher animals.
The elasmobranch pharynx, it seems to me, represents an
advanced stage of a modification which is already indicated in
the ammocoete. This modification consists of a lateral migra-
tion of the dorsal and ventral attachments of the gill arches,
resulting in a lateral enlargement of the central portion of the
pharyngeal cavity and a consequent reduction of the respiratory
part. This lateral migration is indicated by the dorsal at-
tachments of the second pair of gill arches in the lamprey larva.
Attention may also be called to the fact that the primitive
elongated character of the pharynx in the ammocoete tends to
obscure its relation to the elasmobranch pharynx, in which the
length has been reduced with a consequent reduction of the
number and size of the gill slits.
It is necessary to determine the character of the gills in ammo-
coetes in so far that it has been established that the thymus in
all higher forms has a more or less definite relationship to the
gill pouches and gill arches.
Text fig. 1 Model of a segment of the branchial region of a 15 mm. lamprey
larva. Cephalic aspect. The model shows the relationship of the primitive
thymus placodes to the epipharyngeal ridge and the ciliated epithelium, as well
as the relationship of the epipharyngeal ridge to the gill arches and general
branchial cavity. a., atropore; a.p., alimentary pharynx; c.e., ciliated epithe-
lium; d.a., dorsal aorta; ep.r., epipharyngeal ridge; g.a., gill arch; g.l., gill lamel-
lae; n., notochord; p.t.p., primitive thymus placode; r.p., respiratory pharynx;
s.c., spinal cord; v.a., ventral aorta; x., position of accumulations of lymphocytes
in lateral branchial walls.
136 IVAN E. WALLIN
Dohrn (84) made the statement:
the great difference between the Selachian, Teleost and Ganoid bran-
chial apparatus and that of the petromyzon consists therein that the
gill septa and lamellae (Kiemen-blatter und -blattchen) of the former
are directed outward while in the latter they are directed inward.
He further states that this arrangement in the petromyzon
exists from the beginning. ‘This interpretation of the gills of
petromyzon has been accepted in some of the textbooks on
Comparative Anatomy of Vertebrates The basis for this in-
terpretation is undoubtedly found in the position of the carti-
laginous gill bars, which form a complicated branchial basket
in the pharyngeal wall The branchial artery, however, is situ-
ated in the medial gill arch. From this medial gill arch the gill
septum extends caudo-laterally to its attachment in the lateral
wall. The gill lamellae are situated on the anterior and posterior
walls of the septum. The picture of a frontal section of the gills
in the ammocoetes is so much like the picture of a similar sec-
tion of the elasmobranch gills that it is difficult to consider
them as directed in opposite directions. The question resolves
itself ‘nto a choice between the cartilaginous branchial bars
and the branchial aortic arches as a basis of interpretation.
It is evident that the branchial basket of petromyzon is a special
modification meeting the requirements of a specialized mode of
breathing due to the life habits of the adult. The position of
the cartilaginous gill bars must then be considered the result of a
migration from a more medial position. Moreover, the pres-
ence of the ciliated bands in the medial gill arches point to a
direct phylogenetic relationship to the gill arches of amphioxus.
If we consider the gills of the ammocoete as directed inward it
would be necessary to consider as the gill arch, the part of the
respiratory portion of the lateral branchial wall to which the gill
lamella is attached. This would be contrary to the arrangement
of the gills in all other chordate animals.
THYMUS-LIKE STRUCTURES IN AMMOCOETES 137
ORGANOGENESIS OF THE PHARYNX IN THE AMMOCOETES
A complete detailed description of the development of the
branchial region in the lamprey larva isapparently not to be found
in the literature. Separate structures and the condition in a
single or in a limited number of developmental stages, however,
have been described by various investigators. These descrip-
tions have been accurate with the exception of minor details,
but having been hmited to a single stage in most cases they do
not include the changes which occur with the growth of the
larva. There are consequently contradictory statements in
the literature on the pharynx of the ammocoetes and especially
in the part dealing with the ciliated grooves and bands. Fur-
ther, the formation of structures which I interpret as primitive
thymus placodes is closely linked with the changes which occur
in the ciliated bands in the branchial lining.
The following descriptions are based entirely upon my own
material:
The transformations in the early larvae are very rapid so that
in 6 and 7 mm. larvae gill lamellae have formed on the branchial
septa, the pouches open to the outside, and the epithelium is rep-
resented by more than one layer. A system of ciliated epithelial
grooves and bands are present in this stage of development of the
pharynx. They form a connected system which may be looked
upon as beginning in two rather deep diverticula in the caudal
walls of the first pair of gill pouches. From each diverticulum
two ciliated grooves originate, one passing ventro-caudally, the
other dorso-caudally. These will be designated the ventral and
dorsal grooves respectively.
The two ventral grooves converge in a caudal direction as
far as the third pair of gill pouches where they come to lie
close together and parallel to each other near the median line.
Between the two grooves is a median ridge of non-ciliated epi-
thelium which disappears in the fourth pouch where the two cili-
ated grooves fuse to form a single one. A tubular divericulum
passes from the ventral groove into the thyreoid a short distance
caudad of the point where the grooves fuse. A second diverti-
138 IVAN E. WALLIN
culum connects the thyreoid with the fifth pouch. In the
seventh pouch the ciliated groove ends. It is directly continued
by non-ciliated epithelium which, in a few sections caudad,
becomes a ridge. The ciliated groove is a continuous groove
from the fourth to the seventh pouches. The ridge which be-
gins in the seventh pouch gradually becomes high and stalked
in the eighth pouch. The median columnar epithelium becomes
invaginated and is directly continuous into the floor of the oesoph-
agus. Surrounding the Junction it seems to me there is evi-
dence of a vestigial eighth gill arch in which an aortic arch is not
present. The respiratory part of the branchial cavity extends
a short distance caudad of the point of junction between the
pharynx and oesophagus.
The dorsal ciliated grooves arising in the diverticula follow
the course of the first aortic arch to the median dorsal line of the
pharynx. They fuse at this point to form a single ciliated band
which extends caudally the whole length of the branchial cavity
and which is directly continuous into the roof of the oesophagus.
A short distance caudad of the point of origin, this band forms a
rounded ridge which extends to the seventh sac where it is
converted into a groove. The aorta is lodged in the concavity
of the rounded ridge. At the point where the two dorsal grooves
of the first pouch fuse a tongue-like piece of non-ciliated epithe-
lium is pinched off (text fig. 2). Schaffer apparently mistook
this for ciliated epithelium and considered it the end of the fused
ciliated bands.
The first pair of gill arches come together dorsally in the
median line. Their ventral extremities, however, are far apart
and end in the ventro-lateral part of the respiratory pharynx.
Gill lamellae are present only on the caudal surface of the first
gill septum. The second pair of arches are farther apart and
thus they differ from the remaining caudal arches. Their dorsal
attachments are in the angle between the epipharyngeal ridge
and the dorso-medial part of the respiratory pharynx. Ven-
trally, the second gill arches are attached about midway between
the mid-ventral line and the ventro-lateral angle of the respira-
tory pharynx. The dorsal attachments of the third and remain-
THYMUS-LIKE STRUCTURES IN AMMOCOETES 139
ing pairs of gill arches is the ventro-lateral angle of the epi-
pharyngeal ridge. Ventrally, they are attached near the ven-
tral median line, a little to the side of the endostyle. The
second pair of arches are peculiar in that they contain no cili-
Text fig. 2 Camera lucida outline drawings to illustrate the course of the
dorsal ciliated grooves (the ventral grooves are not shown) from the diverticula
in the first pouch to the point where the grooves meet in the median dorsal line
to form a single band of ciliated epithelium. c.g., dorsal ciliated groove; d.a.,
dorsal aorta; e.p., epithelial placode; n., notochord.
140 IVAN E. WALLIN
ated bands. The third and remaining arches have a broad
ciliated band covering the medial and cephalic aspect. These
bands are directly continuous with the ciliated band on the epi-
pharyngeal ridge. ‘They have no connection with the endostyle
in this stage of development and I have been unable to deter-
mine whether such a connection exists or not in younger larvae.
The moving apart of the second pair of gill arches is very
suggestive of an approach to the condition in fishes where the
arches are attached in the lateral part of the roof of the pharynx.
Accompanying this lateral migration there is a loss of the ciliated
band on the arch.
The arrangement of the ciliated bands as described above
does not persist in older larvae. This undoubtedly accounts
for the contradictory descriptions given by Anton Schneider
(79) and Schaffer (95, 1 and 2) and others. Ina larva 9.5 mm.
in length growth and differentiation of the epithelium of the gill
arches has resulted in a new arrangement of the ciliated bands.
This new arrangement has gained its permanent larval condition
Imes mm. larva.
In the older larvae the median dorsal ciliated band which
represents the fused continuation of the dorsal ciliated grooves
of the first arch ends in the median dorsal line between the sec-
ond pair of gill arches. Immediately caudad of the dorsal at-
tachment of the second pair of gill arches two ciliated bands
appear on the ventro-lateral part of the epipharyngeal ridge.
Tracing these bands in a caudal direction, they are seen to come
together and fuse in the median ventral part of the ridge at the
caudal end of the dorsal equivalent of the third gill pouches.
From this single band a branch is given to each of the third pair
of gill arches. In the median line the ciliated band ends as a
pointed process in the angle between the dorsal attachments of
the third pair of gill arches. This arrangement of the ciliated
bands is repeated in the remaining arches and dorsal equiva-
lents of the gill pouches (text fig. 3, and c.e. in text fig. 1). In
the eighth pouch, however, the median ventral fused part does
not give off any lateral branches corresponding to the ones given
off to each gill arch in the third to the seventh arches. ‘This is
THYMUS-LIKE STRUCTURES IN AMMOCOETES 141
due to the nature of the dorsal attachment of what I have as-
sumed must be the eighth vestigial gill arch. This arch, like the
second, is not attached to the epipharyngeal ridge but to the
angle between the ridge and the dorsal wall of the respiratory
pharynx. Cilia, however, are present on the lateral side of the
eighth gill arch. They undoubtedly represent the vestigial
remains of a condition in which this arch had a dorsal attach-
ment to the ridge or its equivalent. The median ciliated band
Text fig. 3 Diagram illustrating the arrangement of the ciliated bands on
the epipharyngeal ridge and the gill arches in a 31 mm. larva. Ventral view.
The gill arches which extend ventrally are here represented as extending laterally.
The ciliated epithelium is represented in heavy black, the non-ciliated by the
stippled part. Roman numbers indicate the gill pouches and Arabic numbers
the gill arches. pl., primitive thymus placodes.
142 IVAN E. WALLIN
of the eighth pouch is directly continuous into the oesophagus.
It is interesting to find that the band divides into two por-
tions within the oesophagus. These perhaps represent the
branches which were given off to the eighth pair of gill arches in
an ancestral form.
Patches of ciliated epithelium are also present on the medial
aspect of each gill arch from the third to the seventh inclusive.
These ciliated patches undoubtedly were a part of the single
ciliated band on the gill arches in the younger larva. With the
growth of the non-ciliated epithelium of the gill arches, these
patches were cut off from the ciliated band. In the older larva
the ciliated band of the gill arch does not occupy the same rela-
tive position that it did in the young larva. The ventral end is
situated on the lateral side of the gill arch. When traced in a
dorsal direction it is found to take a slightly spiral course so
that the dorsal extremity which is continuous into the ciliated
band of the epipharyngeal ridge comes to occupy a cephalo-
medial position. This change in the course of the ciliated band
may also be looked upon as the result of the growth of the non-
ciliated epithelium. The ciliated patches on the medial side
of the gill arch may acquire a sensory function as Schaffer
suggested.
The arrangement of the ciliated epithelium on the epipharyn-
geal ridge in the older larvae is also the result of the growth of
the non-ciliated epithelium. In a larva between 8 and 9 mm. in
length the non-ciliated epithelium of the dorso-medial part of
the gill arches begins to invade the ciliated epithelium of the
epipharyngeal ridge. As a result of this invasion the continuity
of the ciliated band on the epipharyngeal ridge is lost. The two
cords of invading epithelium from the opposing gill arches fuse
in the median ventral line of the ridge. The invasion is continued
in a caudal direction dividing the ciliated band into two portions
which are pushed laterally. This fused portion (pl., text fig. 3)
becomes thicker and broader in a caudal direction and ends a
short distance cephalad to the attachment of the next pair of
gill arches. At the caudal end of this invading epithelium the
subsequent growth does not divide the ciliated epithelium fur-
THYMUS-LIKE STRUCTURES IN AMMOCOETES 143
ther, but produced a tongue-like process which projects into the
pharyngeal cavity (similar to the tongue-like non-ciliated epi-
thelial process represented in text figure 2).
The non-ciliated epithelium which has invaded the ciliated
epithelium of the epipharyngeal ridge begins to show histogenetic
activities in a larva between 20 and 30 mm. in length. The
nuclei of the cells of these areas, or placodes, wander out into the
underlying connective tissues and are transformed into lympho-
eyte-like cells. A study of the histogenetic processes in these
areas in various developmental stages leads to the conclusion
that these areas represent specialized regions of the branchial
epithelium which are suggestive of primitive thymus structures.
From the foregoing description it is evident that there are in
all seven placodes. The seventh and the first are smaller than
the remaining ones but they take part in the histogenetic proc-
esses and are therefore to be considered true functional placodes.
The placodes increase in size with the growth of the larva.
In the mature larva, however, they show a depletion of cells.
When the larva undergoes metamorphosis the whole structural
arrangement of the branchial-region is altered. In the single
specimen of a transforming larva of my collection, the adult
arrangement has been attained, so I am unable to describe the
nature of this process. In this transforming specimen I have
also been unable to find any remains of the epithelial placodes of
the larva. Serial sections of the branchial region of an adult
lamprey have also been examined but with negative results.
It is evident that an involution of the placodal organ has taken
place as one would expect of a thymus. This involution began
in the maturing larva and was completed in the early stages of
metamorphosis.
HISTOGENESIS
Early development of the pharyngeal wall in Petromyzon marinus
unicolor, Lampetra wilderi
The search for a thymus in the lamprey larva has revealed an
unusual accumulation of lymphocytes in the lateral walls of the
branchial cavity. These accumulations were first observed by
144 IVAN E. WALLIN
Schaffer (94) and later described more in detail by Giacomini
(00, 1 and 2) and Castellaneta (13). The origin of these
lymphocytes as well as the cause for their accumulation in these
places has not been determined and consequently constitutes a
problem to be solved in the consideration of a possible thymus
structure in this animal. The descriptions in the literature
have been limited to single stages of development and are con-
sequently incomplete. The following descriptions are based on.
my own material and includes the essential developmental
stages:
The branchial cavity of a 5 mm..larva represents a very simple
condition. The gill pouches are present as wide evaginations
extending to the ectoderm in the mid-lateral plane leaving the
gills as simple projections of the lateral endodermal walls.
Loose mesenchyma cells fill up the space within the gill. The
aortic arches are forming near the free medial border of the
gills, but the vascularization of the body of the gill has not begun
as yet. Although the larva contains a great quantity of yolk
in this stage the branchial region is quite free from it.
The epithelium lining the branchial cavity including the gills
consists of a single layer of columnar cells. Dorsal and ven-
tral to the mid-lateral plane of each gill pouch and correspond-
ing to the position of the future lymphoid accumulations of
Schaffer the endoderm shows a slight thickening (fig. 2). In
these places which may be called placodes the cells have lost
their columnar shape and their outlines have more or less dis-
appeared. The area appears to be taking on a syncytial char-
acter in which the nuclei do not have any definite grouping.
Marked changes have occurred in these placodes in a 9.5 mm.
larva. In general, the placodes have become enlarged both in
thickness and area (fig. 3). Cell outlines are practically all
obliterated. The cytoplasm is streaky in appearance suggest-
ing a degeneration. The nuclei exhibit variations in character.
Some are very dark with a large chromatin content while others
are pale and contain a small amount of chromatin. Still others
show amoeboid characters. I have not been able to determine
whether all these nuclei are indigenous to the placode. The
THYMUS-LIKE STRUCTURES IN AMMOCOETES 145
general epithelium of the branchial cavity has also acquired a
new character in this stage. Beneath the placodes and in
direct contact with them the peribranchial blood channels are
forming. It is difficult to distinguish an endothelial lining of
these channels in all cases.
The degeneration of the placode has progressed farther in a ~
15 mm. larva (fig. 4). In places the cytoplasm has taken the
stain very faintly.. Scattered about in the placode are streaks of
cytoplasm which are very deeply stained. Vacuoles are also
present. The nuclei appear to be fewer in number than in the
earlier stages. They appear more constant in their general
appearance and chromatin content. The amoeboid character
of the nuclei has also become more prominent. Some nuclei
have taken up positions at the surface of the placode and the
cytoplasm appears to be cutting off a layer of flattened cell (fig.
4, s.l.). The formation of a layer of flat cells at the surface of
the general epithelium was begun in a much earlier stage of
development.
The changes which occur in these placodes in older larvae
approximate the character represented in the 63 mm. larva
(fig. 1). It is a significant fact that cells in mitosis have not
been seen in any stage of the development of these placodes.
Furthermore, patches of epithelr'um giving the appearance of a
degeneration are present in various other parts of the branchial
lining, especially at the lateral attachments of the gill septa.
Lymphocytes are present in the placodes in the older larvae,
but they are also present in the general branchial epithelium.
They do, however, occur in greater numbers at these placodes.
From these brief descriptions it is apparent that these placodes
do not represent active anlagen of a future structure. Their
development and structure do not suggest anything which might
indicate their significance.
The lymphocyte accumulations in relation to the above de-
scribed placodes are contained within vascular channels. These
vascular channels contain red blood cells, and as has been shown
by Mozejko (10) and others they are in communication with
THE AMERICAN JOURNAL OF ANATOMY, VOL. 22, No. 1
146 IVAN E. WALLIN
similar channels within the body of the gill as well as with the
definitive blood vessels of the pharynx.
Lymphocytes begin to make their first appearance in the blood
in larvae of about 9 mm. length. They increase in number
with the growth of the larvae, but chiefly remain outside of the
main blood vessels. They are especially abundant in the peri-
vascular spaces of the gill arches.
The accumulations of lymphocytes in the lateral branchial
walls are foreign to these situations so far as their origin is con-
eerned. Furthermore, the epithelial placodes in these situations
together with the lymphoid accumulations do not exhibit the
characters which are essential in either a well-established or
rudimentary thymus. I can offer no suggestion in regard to any
special significance of these accumulations. They appear to be
merely a part of a rich accumulation of lymphocytes in the con-
nective tissue spaces of the branchial region. It is probable
that the apparently degenerating placodes play a réle of attrac-
tion for lymphocytes.
Epipharyngeal placodes
The placodes in the epipharyngeal ridge are present in an un-
differentiated condition in a 15 mm. larva. They form distinct
masses of cells in the mid-ventral part of the epipharyngeal ridge
between the ciliated bands. They are very nearly circular in
outline in a transverse section, producing a bulging into the
interior of the ridge (figs. 5 and 6). A loose mesenchymatous
tissue caps the dorsal surface of the placodes. Red blood cells
are occasionally present in the spaces of the mesenchymal
tissue. These spaces are apparently in communication with the
dorsal aorta by means of minute apertures and are directly con-
tinuous with similar spaces in the connective tissue of the gill
arches. Through the spaces of the gill arches a communication
is also made with the peribranchial sinuses and the perivascular
spaces in the gills.
Within the placode the cells are in an active state of pro-
liferation. The nuclei of the resting cells are rather clear
THYMUS-LIKE STRUCTURES IN AMMOCOETES 147
structures with the chromatin generally collected into small
lumps situated next to the nuclear membrane. The nuclei are
smaller than those of the ciliated epithelial cells. Cell outlines
are more or less distinct in the placodes. <A peculiar type of
vacuolization is in progress in some of the cells in which the
complete cell becomes vacuolated leaving the protoplasmic
remains as free bodies within the hollow cell. The proto-
plasmic bodies in these cases are small lumps of nucleated
protoplasm in which the nuclear material generally stains an
intense black and the cytoplasm a light red. These protoplasmic
bodies are not limited to the epithelial placodes, but may be
found everywhere in the branchial epithelium, especially in the
15 mm. larva.
A layer of flat cells clothes the surface of the placode. This
layer is not distinct in every section and may easily be over-
looked. ‘At the connective tissue border of the placode a base-
ment membrane sharply marks off the epithelium from the
mesoderm (b.m., fig. 5). Lymphocytes have not been found
in the placodes in a 15 mm. larva although they are present in
the blood. They may be seen, however, in the general branchial
epithelium and also in the ciliated epithelium (lm., fig. 6).
The placodes have increased considerably in size in a 31 mm.
larva. The mesenchymatous tissue which was present above the
placode in the 15 mm. stage has changed to connective tissue
(fig. 7). Large spaces containing various kinds of blood cells
are present in this connective tissue. Larger and smaller nuclei —
may be seen in the walls of these spaces. The smaller undoubt-
edly represent the nuclei of endothelial cells. The larger, how-
ever, are apparently derived from the placode and are in a stage
of migration into the vascular spaces. It is doubtful whether
these spaces should be considered true blood channels. While
red blood cells are quite abundant in the spaces in this stage of
development they are practically absent in them in the full
grown larva. It is probable that they represent a primitive
type of lymph vessels, as has been suggested by various authors.
The connective tissue is of the fibrous variety in which the
individual fibers are quite slender. The fibers interlace to
148 IVAN E. WALLIN
form a loose mesh work. Figure 7 represents a transverse sec-
tion through the cephalic part of a placode with its neighboring
connective tissue and the ciliated epithelium of one side. In
such a region the nuclear elements are very scarce in the con-
nective tissue when compared to the region above the central
part of aplacode. ‘The basement membrane which is present only
on the right-hand side in the section illustrated in figure 7 (b.m.)
bridges across the entire placode a few sections cephalad of the
one illustrated. In the central part there is no line of demarca-
tion between the placode and the connective tissue. The cyto-
plasm of the placode in this place is directly continuous with the
connective tissue. :
The cells within the placode have greatly increased in num-
bers in this stage of development. Near the free surface of the
placode they are loosened from each other, displaying their
rounded outlines distinctly. Toward the deeper part of the
placode the cells become oblong in shape. Near the connective
tissue border the cell outlines are lost which gives the appear-
ance of a syncytium. The nuclei of the cells in the placode are
not unlike the nuclei of the ciliated and the general branchial
epithelium in their general morphological characters, except in
size. They are smaller than the nuclei of the ciliated and gen-
eral epithelium. The chromatin of the nuclei, for the most part,
is collected into a single lump which stains a reddish-purple
with the haematoxylin-eosin stain. The nuclei also change
from a circular to an oblong outline from the free surface of the
placode to the connective tissue border. At the place where
the cytoplasm of the placode is continuous with the connective
tissue, the nuclei become quite elongated, having the appear-
ance suggestive of a migration into the connective tissue. This
migratory appearance is more prominent at the central part of
the placode. Figure 10 represents a part of a transverse sec-
tion from the central region of the placode. The two lower
nuclei marked a in the figure lie in the cytoplasm of the placode.
All the nuclei and cells above this level are in the connective
tissue and spaces above the placode. The nuclei in the connec-
tive tissue show degrees of gradual variations in morphological
THYMUS-LIKE STRUCTURES IN AMMOCOETES 149
characters from the typical epithelial nucleus of the placode to
the mature lymphocyte-like cell. Nuclei showing these degrees
of variation may all be found in a single section. Figures 10
and 11 show the most obvious stages in this gradual variation.
The nuclei marked a are typical placode epithelium nuclei ap-
parently in a state of emigration. The nucleus marked 6 is in the
connective tissue. The chromatin in this nucleus is apparently
breaking up into a number of granules, a process which has
proceeded farther in nucleus c. In nucleus d the chromatin
granules are apparently arranging themselves on the nuclear
membrane, an arrangement which has been completely attained
in nucleus e. Nucleus e further shows a tendency towards ac-
quiring a circular outline which becomes more manifest in
nucleus f. Nucleus f also shows a reduction in size. Nucleus g
(fig. 11) has a circular outline and further shows a change in the
character of the protoplasm. The nucleus h shows a still
further reduction in size, the protoplasm stains darker as does
also the chromatin. The chromatin, further, forms a continuous
layer at the periphery. In 7 (figs. 10 and 11) the nuclei have
acquired a thin covering of cytoplasm which is not visible at all
points of the nuclear surface. The cytoplasm stains a gray-
blue. The nucleoplasm and the chromatin of these cells take
the stain more intensely than the nucleus h. These cells have also
become free from the connective tissue mesh work. In the
cells 7 the nucleoplasm stains a deep purple. The chromatin
appears to have left the nuclear membrane and is now present
as granules scattered about in the nucleus. In some nuclei the
chromatin granules are connected together by slender processes,
in others this is apparently not the case. Still other cells show
nuclei in which the chromatin is represented by a single large
lump. These cells (j, figs. 10 and 11) represent the typical
lymphocyte-like cell in this region of the 31 mm. larva. Some
of these cells may be found in which the nucleoplasm stains a
gray-blue (k, fig. 10). They are similar to the lymphocytes in
older larvae and may either represent a final stage in the de-
velopment of the cells, or they may represent cells foreign to
this locality.
150 IVAN E. WALLIN
From the above described transitional conditions and from a
study of the stained sections, I can draw no other conclusion
than that, the nuclei of the epithelial placode transform into
lymphocyte-like cells. It is a significant circumstance that the
nuclei alone migrate from the placode, i.e., no cytoplasm is vis-
ible. Complete cells bearing epithelial characters may be found
in the connective tissue spaces. However, I have never found
them migrating from the placode while I have found migrations
of the complete cell from the epithelium of other regions.
Cells in mitosis may be seen occasionally in the placodes of
the 31 mm. larva. Cells in a state of amitotic division, how-
ever, are quite abundant in a 44 mm. larva, suggesting that
cell-proliferation takes place chiefly by simple fission. Figure
15 shows the nucleus of a placode cell apparently in a process of
simple fission. Mitotic cells are especially scarce in the con-
nective tissue above the placode. A single instance has been
found and is represented in figure 18. It is quite evident from
the lack of mitotic or amitotic cells or nuclei in the connective
tissue that cells or nuclei are not being formed in any significant
quantities in this situation.
Transformation stages have not been found within the plac-
ode in the 31 mm. larva. Lymphocyte-like cells, however, are
present in the placodes. Their presence may be accounted for
by means of an immigration from the connective tissue.
The further development of the placodes is a repetition of the
above-described processes except that the transformation is more
rapid and begins within the placode. Figure 8 represents a part
of a transverse section of the placode and the connective tissue
above it in a 44 mm. larva. The illustration was drawn to the
same magnification as figure 7. The nuclei in the placode are
elongated and show amoeboid characters. They also appear
to be in an active state of emigration. The transformation
process appears to have begun in the placode in this stage.
The nuclei near the connective tissue border have taken on
characters which approach the characters of some of the nuclei
in the connective tissue. This change is shown in the staining
reaction, the condition of the chromatin, and the shape of the
THYMUS-LIKE STRUCTURES IN AMMOCOETES Lot
nuclei. The nuclei at the border show a tendency to stain blue,
the chromatin takes a darker stain, and in some cases is broken
up into granules, and the nuclei approach the globular shape.
The transformation of the nuclei in the connective tissue appears
to be of the same character as in the 31 mm. stage, but appar-
ently more rapid. Nuclei may occasionally be found in the plac-
ode which show phagocytic properties. Figure 14 represents a
placode nucleus in the act of engulfing protoplasmic bodies.
The spaces in the connective tissue in the 44 mm. larva appear
to be smaller than in the 31 mm. stage. Some of them have a
distinc wall while others appear like transient spaces in the
connective tissue. Red blood cells are only occasionally seen
in the connective tissue spaces of this stage.
The placodes in a 63 mm. larva are larger in area but thinner
than in the preceding stages. The nuclei of the epithelial cells
of the placode have lost their original character. The chromatin
is no longer represented by a single large lump, but is present
in the form of granules corresponding to the chromatin in the
nuclei which had migrated into the connective tissue in the 3]
mm. stage. The number of lymphocyte-like cells has increased
considerably within the placode. All the stages of transforma-
tion from epithelial nucleus to the mature lymphocyte-like cell
may be found within the placode in this stage of development.
A basement membrane is re-forming at the connective tissue
border of the placode. The ‘vascular spaces’ of the connective
tissue are now chiefly limited to the peripheral part of the whole
connective tissue within the ventral half of the epipharyngeal
ridge. The mature lymphocyte-like cells are chiefly located in
these channels, leaving the central connective tissue core quite
free from cells. The central core consequently has a much
lighter appearance. Some nuclei are present in the central core,
the morphological characters of which are similar to the charac-
ters of connective tissue nuclei in other parts of the body.
Other nuclei may occasionally be seen in which the characters
agree with the various transformation stages of the lympho-
cyte-like formation shown in younger larvae.
1p2 IVAN E. WALLIN
The activities within the placodes of the full grown larva (120
mm.) have diminished and are apparently approaching a condi-
tion of cessation. The number of epithelial nuclei has been
reduced considerably. ‘Transitional stages may be found, but
are quite scarce. Mature lymphocyte-like cells are also pres-
ent, but not in great numbers. A definite basement membrane
is now present at the connective tissue border of the placode.
Figure 9 represents a portion of a transverse section of the
placode and the tissue above it in a 120 mm. larva. The sec-
tion is taken near the cephalic end of the placode. In such a
region a peculiar formation has occurred in the connective
tissue, the significance of which I am quite unable to explain.
This formation consists of what appears to be red blood cells
held in the meshes .of the connective tissue (a, fig. 9). The cells
have the morphological characters of the red blood cells. The
cytoplasm has a decided yellow tint, while the pale nuclei have a
green tint. In some cases what appears to be the nuclei have
morphological characters similar to the lymphocyte-like cells.
These formations are present in the periphery of the whole con-
nective tissue. A section through the central part of the plac-
ode would show the same character that was indicated in the 63
mm. larva, that is, a central core of connective tissue in which there
are no ‘vascular channels’ surrounded by a ‘vascular area.’
The tissue between the ‘vascular channels’ in the 120 mm. larva
consists entirely of the peculiar tissue just described.
Development of lymphocytes
A brief description of the general development of lympho-
cytes in the petromyzon larva is here given since the nature of
this formation in the advanced larvae has a.direct bearing on the
interpretation of the histogenetic processes in the above de-
scribed placodes. My observations do not include the first
appearance and development of the blood in the embryo, but
begin with the development in the 5 mm. larva. The nature
of the blood formation in this stage of larval development need
not be described here for the reason that it occurs at a time when
the placodes have not begun to form. However, in larvae
THYMUS-LIKE STRUCTURES IN AMMOCOETES ep)
ranging from 9.5 mm. in length up to the mature individual,
blood cells develop from the epithelial cells of the gills, gill
arches, and probably the branchial wall by a process of trans-
formation. It is the blood formation occurring in the gills and
gill arches which is of especial interest in connection with the
histogenesis in the placodes. The description of this formation
will be limited to the formation of lymphocytes only, in the 31
mm. larva.
The similarity of the cytoplasm of the gill epithelium to the
cytoplasm of some of the blood cells was early noticed. This
similarity was found to be due to an actual relationship between
the two kinds of cells and thus not a mere coincidence. This
relationship was demonstrated when epithelial cells were found
migrating through the walls into the lumen of the blood channels
in the gill. Figure 13 represents a part of the gill epithelium
and a blood vessel and shows an epithelial cell beginning its
migration into the vessel. Figure 12a shows another epithelial
cell in the state of migration, almost half of the cell in this case
is inside of the vessel. The cells to the left in figure 12 repre-
sent blood cells (in the vessel) in various stages of transformation.
In this figure, the chief stages in the transformation of the epi-
thelial cells to lymphocytes are represented. The lettering a
to h in the figure shows the line of transition from an epithelial
to the mature lymphocyte.
In this formation of lymphocytes, it is noteworthy that the
entire epithelial cell migrates from the ‘epithelium’ and takes
part in the transformation. The transformation consists of a
reduction in the size of the nucleus and also in the amount of
cytoplasm. The cytoplasm retains its staining qualities through
these changes so that even in the mature lymphocyte a cytoplas-
mic ring which stains red may be seen in many instances. It is
very seldom that a lymphocyte containing a cytoplasm which
stains a blue or gray-blue is. seen in these situations. All the
transforming cells have a cytoplasm which stains red with the
haematoxylin-eosin stain.
Although some of the epithelial cells in this transformation
migrate directly into the blood vessels, the great majority wan-
154 IVAN E. WALLIN
der into the perivascular spaces and undergo their transformation
in these places. The sluggish character of the blood flow in
these spaces must account for the retention of the large num-
ber of transforming and mature lymphocytes which are present
in these situations. The entrance of these cells into the main
blood vessels is of a slow nature.
The tall epithelial cells in the dorsal part of the epipharyngeal
ridge also enter into the blood formation. Figure 16 shows a
cell taken from the space in the connective tissue of the dorsal
part of the epipharyngeal ridge. The nucleus has the morpho-
logical characters of the epithelial nuclei. It appears to be in a
state of simple fission. The cell in figure 17 was taken from
the same locality. Two nuclei are present in this cell which still
show the epithelial character.
Histogenetic comparisons between cells arising from placodes and
lymphocytes
In the study of the histogenetic processes in the placodes it
was shown by means of various transitional stages that the epi-
thelial cells of the placode transform into lymphocyte-like cells.
Lymphocytes were shown to develop from the ‘epithelial’ cells
of the gills and gill arches. The lymphocyte-like cells formed
from the placodes do not have the same mode of development nor
do the transitional forms have the same morphological charac-
ters as the lymphocytes and transitional forms developed from
the gill and gill arch ‘epithelium.’ In the placode the nuclei
alone migrate away from the original epithelial bed and the
transformation occurs in the connective tissue meshwork. The
complete cell migrates away from the epithelial bed in the gills
and gill arches, the transformation occurs in the perivascular
spaces and the blood vessels. A small amount of cytoplasm
becomes visible in the placode ‘lymphocyte’ just before it attains
its maturity. This cytoplasm stains a gray-blue. The cyto-
plasm of the gill and gill arch lymphocytes represent the original
cytoplasm of the ‘epithelial’ cells and stains red. These im-
portant differences in the lymphocytes and lymphocyte-like cells
THYMUS-LIKE STRUCTURES IN AMMOCOETES 155
occur in the same section and thus cannot be attributed to differ-
ence of technique. A lymphocyte with red cytoplasm may occa-
sionally be found in the epipharyngeal ridge just as a ‘lympho-
cyte’ with gray-blue cytoplasm may occasionally be found in the
gill region. The great majority of ‘lymphocytes’ in the placode
region, however, contain cytoplasm which stains gray-blue.
It was also pointed out above that the lymphocytes in the
gill region are chiefly the type which have red cytoplasm. The
presence of the lymphocytes with red cytoplasm in the placode
region and the type with gray-blue cytoplasm in the gill region
may be accounted for by migration from their seats of origin.
They may also be brought to these situations by the flow of the
blood.
On account of the morphological difference of the develop-
ing lymphocytes in the gill region and lymphocyte-like cells of
the placodes, the conclusion seems justifiable that the placodes
are segregated portions of the ‘epithelium’ representing indi-
vidual organs which produce cells of a lymphocyte appearance,
but differing from the lymphocytes formed in the ‘epithelium’
of the gills.
. DISCUSSION
The data submitted in the consideration of the lymphocyte
accumulations in the lateral branchial wall of the lamprey larva
does not supply any evidence that these formations represent
primitive thymus anlagen. Although placode-like formations
are present in the lateral branchial wall, similar formations are
also present in other parts of the pharyngeal epithelium.
An important component of the thymus of higher animals is a
reticulum. In my study of the thymus-like placodes in the lam-
prey larva, I have been unable to find any undisputable evidence
of a reticulum in the placode. At the connective tissue border
of the placode the epithelial cytoplasm apparently has a fibrous
character (fig. 10). I have been unable to determine whether
this represents connective tissue or transformed epithelial cyto-
plasm. Judging by its appearance and position it probably
represents connective tissue which has been invaded by cyto-
156 IVAN E. WALLIN
plasm from the placode. The connective tissue outside the
placode plays the role of a reticulum insofar that the trans-
formation of the epithelial nuclei occur within its meshes.
Hassal’s corpuscles, or any structures comparable to them
have not been found in the placodes or in the connective tissue
outside of the placode.
The history of the placodes in the successive developmental
stages indicates a gradual involution of the placodes. The
maximum size of the placodes occurs in a larva of 50 to 60 mm. in
length. From this stage of development the placodes diminish in
size so that in the mature larva very few lymphocyte-like cells
remain. In the transformation of the larva, Nestler (10) main-
tains that the oesophagus of the adult is formed by a transforma-
tion of ‘‘the under edge of the dorsal fold in the branchial
chamber” (the epipharyngeal ridge). If such a process occurs,
is is only after the histogenetic activities in the placodes have
ceased and consequently does not affect the status of an earlier
thymic function in these placodes.
An examination of the descriptions given in the preceding
pages give the impression that the primitive thymus placodes and
lymphocytes are formed from an endodermal epithelium. While
I am not ready at this time to supply the evidence, the changes
which occur in the general branchial epithelium in the early
stages of development seem to point to a general fusion of the
original endoderm with the underlying mesenchyma. The
character of the epithelium in the more advanced larvae has such
an important bearing on the interpretation of the histogenesis
of the primitive thymus cells and lymphocytes that a separate
and detailed study of this process seems warranted.
In a recent article on the Development of the Human Pharynx,
Kingsbury (’15) discusses the intrinsic and extrinsic factors in
thymus formation and challenges the view that the thymus is a
branchiomeric organ definitely located in the branchial epithe-
lum. The basis for this interpretation
is found in the recognition that it is a structure whose appearance is
determined by extrinsic factors of relation and position and not in-
trinsic factors located in any particular group of cells. In support of
THYMUS-LIKE STRUCTURES IN AMMOCOETES roy
such an interpretation and giving us, I believe, a better comprehension
of its morphologic significance, we have the fundamental plan of its
histogenesis.
The true nature of the endodermal-mesenchymal relationship
in the ammocoete pharynx has not been definitely determined.
Whatever these extrinsic factors may be, they are apparently of
the same nature in the thymus-like placodes and the lympho-
eyte-forming ‘epithelium’ of the branchial arches. The prod-
ucts of these two regions, however, are not similar and it seems
to me that this dissimilarity can only be explained on the basis
of an intrinsic value or specificity of the ‘epithelium’ of the
placode.
The nature of the formation of lymphocytes and the primitive
thymus placodes in the lamprey larva point to an ontogenetic
relationship in the histogenesis of thymus cells and lympho-
cytes. The branchial region of the lamprey larva may be looked
upon as possessing general lymphocyte-forming properties in
which the primitive thymus placodes represent specialized regions
of the general lymphocyte-forming ‘epithelium.’
SUMMARY
From the evidence obtained in this investigation of the
ammocoetes the following conclusions seem justified:
The placodes in the lateral branchial wall are apparently
patches of degenerating epithelium and have nothing to do with
a thymus structure. The collection of lymphocytes at these
places are foreign to this situation so far as their origin is con-
cerned.
The gills in the ammocoetes are homologous with and extend
in the same direction as the gills in elasmobranchs.
The branchial ‘epithelium’ does not represent a pure endo-
dermal epithelium. This ‘epithelium’ develops haemopoetic
properties in the advanced larva. .
‘Epithelium’ from the gill arches invades the ciliated epithe-
lium of the epipharyngeal ridge and produces placodes. These
placodes have a relationship to the gill arches and gill pouches
which makes them homologous with the thymus placodes of
158 IVAN E. WALLIN
elasmobranchs and are to be considered primitive thymus
structures.
The lymphocyte-like cells which originate in the primitive thy-
mus placodes have different morphological characters and have a
different mode of formation than the lymphocytes which are
formed in the gill arches and lamellae.
This investigation has been pursued in the laboratories of anat-
omy at Cornell University Medical School and Marquette Uni-
versity Medical School. While I hope to have established a prim-
itive thymus structure in the ammocoetes, many of the important
problems of the histogenesis of the lymphocytes and primitive
thymus cells must be left undecided until more exhaustive
investigations can be completed.
BIBLIOGRAPHY
ANKARSVARD, G., UND Hammar, J. 1913 Zur Kenntnis der Ganoidenthymus.
Zool. Jahrb. Abt. f. Anat. u. Ontog. der Tierre, Bd. 36, p. 3.
CASTELLANETA, V. 1913 Sulla questione del timio in ‘Ammocoetes.’ Monitore
zool. Italiano, Anno 24, pp. 161-174.
Cunnincuam, J. Y. 1887 Dr. Dohrn’s inquiries into the evolution of organs
in the chordata. Quart. Journ. of Micr. Science, vol. 27, pp. 265-266.
Dourn, A. 1884 Studien zur Urgeschichte des Wirbeltierkorpers. IV. Die
Entwickelung und Differenzierung der Kiemenbogen der Selachier.
Mitteil. a. d. Zool. Station zu Neapel, Bd. 5.
1885 Studien zur Urgeschichte des Wirebeltierkorpers; VII. Entste-
hung und Bedeutung der Glandula Thyreoids; VIII. Die Thyreoidea
bei Petromyzon, Amphioxus und den Tunikaten, Mitteil. d. Zool.
Station zu Neapel, Bd. 6, pp. 44-92.
GracomInI, E. 1900 a Sulla Struttrua dells branchiedei Petromyzonti. Monit.
Zool. Ital., Anno 11, Suppl. 9-10.
1900 b Ibid. (cited from Oppel ’05).
GorTTE, A. 1875 Die Entwickelungsgeschichte der Unke. Leipzig (cited from
Hammar, ’10).
1890 Entwickelungsgeschichte des Flussneumauges. Hamburg and
Leipzig.
Mouuisr, 8. 1906 Die Entwickelung von Blut und Gefassen. In Hertwig’s
Handbuch der vegl. u. exp. Entwickelungsgeschichte der Wirbeltiere,
Jena.
MozesKo 1910 Uber die Injektion des Vascularsystems von Petromyzon fluvia-
talis. Zeitschr. f. wiss. Mikrosk., Bd. 27.
1911 Uber den Bau und den morphologischen Wert des Vascularsys-
tem der Petromyzon. Anat. Anz., Bd. 40.
THYMUS-LIKE STRUCTURES IN AMMOCOETES 159
Rabu, C. 1886 Zur Bildungsgeschichte des Halses. Prager Med. Woch., Bd.
11, p. 52 (cited from Hammar, ’10). 3
Raruke, H. 1827 Bemerkung uber den imeren Bau des Querder (Ammocoetes
branchialis) und des Kleinen Neunauges (Petromyzon Planeri (cited
from Oppel, ’05).
Scnarrer, J. 1894 Uber die Thymusanlage bei Petromyzon Planeri Sitzungsb.
d. K. Akad. d. Wiss. Wien., Bd. 103, p. 3.
1895a Zur Kenntnis des Histologischen und Anatomischen Baues
von Ammocoetes. Anat. anz., Bd. 10, pp. 697-708.
1895 b Uber das Epithel des Kiemensarmes von Ammocoetes nebst
Bemerkungen uber intraepitheliale drusen. Arch. f. Mikr. Anat.,
Bd. 45, pp. 294-338.
1906 Berichtigung, die Schilddriise von Myxine betreffend. Anat.
Anz., Bd. 28.
Scuneiper, A. 1879 Beitr. zur Vergl. Anatomie und Entwickelungsgeschichte
der Wirbeltiere, Berlin.
Scuuttze, M. 1856 Die Entwickelungsgeschichte von Petromyzon Planeri.
Naturkundige Verhandel, van d. hollandsche Maatschappij. d. Weten-
schappen te Haarlem, II Versam, d. 12, p. 28 (cited from Hammer,
710).
Suiptey, A. E. 1887 Onsome points in the development of Petromyzon fluvia-
tilia. Quar. Journ. of Mict. Sc., vol. 27, pp. 325-371.
Srannius, H. 1854 Handbuch der Anatomie der Wirbelthiere (cited from
Schaffer, ’94).
Stockarp, C. R. 1906 The development of the thyroid gland in Bdellostoma
Stouti. Anat. Anz., Bd. 29.
WHEELER 1899 The development of the urogenital organs of the lamprey.
Zool. Jahrb., Bd. 13.
- Witty, A. 1894 Amphioxus and the ancestry of the vertebrates. New York.
PLATE 1
EXPLANATION OF FIGURES
All figures were drawn with the aid of the camera lucida. Higgin’s carmine
and true blue inks were used to reproduce the colors of the stained sections repre-
sented in the colored plate.
1 Lymphoid accumulation in the lateral branchial wall of a 63 mm. larva.
Ep., Endodermal epithelium; End., endothelium of blood sinus; :b.b.s., peri-
branchial blood sinus; trab., connective tissue trabecula in blood sinus. (75
oil immersion obj., ocular No. 3.)
2 Portion of a frontal section of a5 mm. larva showing the epithelial placode
in the lateral branchial wall. EHct., ectoderm; End., endoderm; Mes., mesen-
chyma. (-'s oil immer. obj., ocular No. 3.)
3 Epithelial placode in lateral branchial wall of a 9.5 mm. larva. Frontal
section. Am.n., amoeboid nuclei; b.c., red blood cells; lm., longitudinal muscle
fibers; ¢m., transverse muscle fibers. (;'s oil immer. obj., ocular No. 3.)
4 Epithelial placode in lateral branchial wall of a 15 mm. larva. Frontal
section. pb.b.s., peri-branchial blood sinus; s.l., layer of flat cells forming at
surface of placode. (;'; oil immer. obj., ocular No. 3.)
160
PLATE 1
THYMUS-LIKE STRUCTURES IN AMMOCOETES
IVAN E. WALLIN
161
THE AMERICAN JOURNAL OF ANATOMY, VOL. 22, No. 1
PLATE 2
EXPLANATION OF FIGURES
5 Epipharyngeal ridge containing primitive thymus p'acode from a 15 mm.
larva. d.a., dorsal aorta; mes., mesenchyma containing vascular spaces; pl.,
primitive thymus placode; b.m., basement membrane separating placode from
mesenchyma. (,'5 oil immer. obj., ocular No. 3.)
6 Primitive thymus placode in 15 mm. larva. Im., lymphocyte; mes.,
mesenchyma; v., vacuoles containing protoplasmic bodies. (,/; oil immer. obj.,
comp. ocular No. 12.)
7 Primitive thymus placode in a 31 mm. larva (ventral surface to the left).
ep., nuclei derived from the placode; c.n., connective tissue nuclei; b.m., remains
of basement membrane. (4: oil immer. obj., ocular No. 3.)
162
THYMUS-LIKE STRUCTURES IN AMMOCOETES PLATE 2
IVAN E. WALLIN
163
PLATE 3
EXPLANATION OF FIGURES
8 Primitive thymus placode in a 44 mm. larva. Ventral surface to the
right. (,'; oil immer. obj., ocular No. 3.)
9 Portion of primitive thymus placode in a 120 mm. larva.
ment membrane; x., cells which are apparently red blood cells held in the con-
b.m., base-
nective tissue. (,4 oil immer. obj., ocular No. 3.)
THYMUS-LIKE STRUCTURES IN AMMOCOETES PLATE 3
IVAN E. WALLIN
PLATE 4
EXPLANATION OF FIGURES
10 A small portion of a primitive thymus placode and the connective tissue
in relation to it in a3l mm. larva. The lettering a to 7 shows the line of transi-
tion from the typical epithelial nucleus (a) to the completed lymphocyte-like
cell (j). (4's oil immer. obj., comp. ocular No. 12.)
11 Transforming cells from primitive thymus placode of a 31 mm. larva.
Cells g and h (not represented in fig. 10), complete the series of transforming
cells shown in figure 10. c¢.f.c., connective tissue nucleus. (4/; oil immer. obj.,
comp. ocular No. 3.)
12 Portion of the epithelium of a gill in a 31 mm. larva showing the migra-
tion of an epithelial cell (a) into a blood vessel. Cells in the left part of the
figure (a to h) show various stages of transformation of the epithelial cell to
lymphocyte. ery., red blood cells; 7, blood cell in vessel in which the nucleus
appears to be dividing; 7., blood cell in vessel in which there are two nuclei.
(js oil immer. obj., comp. ocular No. 12.)
13. Epithelial cell beginning migration into blood vessel. (;'s oil immer. obj.,
comp. ocular No. 12.)
14 Nucleus in primitive thymus placode showing phagocytic properties.
(5 oil immer. obj., comp. ocular No. 12.)
15 Nucleus in primitive thymus placode dividing by simple fission. (,'s oil
immer. obj., comp. ocular No. 12.)
16 Epithelial cell found in a connective tissue space in dorsal part of epi-
pharyngeal ridge. Nucleus beginning to divide. (44 oil immer. obj., comp.
ocular No. 12.)
17 Cell found in a connective tissue space in dorsal part of epipharyngeal
ridge. Two nuclei in the cell which still retains epithelial characters. (,'s oil
immer. obj., comp. ocular No. 12.) te
18 Connective tissue nucleus dividing by simple fission. (;4 oil immer.
obj., comp. ocular No. 12.)
166
THYMUS-LIKE STRUCTURES IN AMMOCOETES PLATE 4
IVAN E. WALLIN
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BEHAVIOR OF CROSS STRIATED MUSCLE IN
TISSUE CULTURES
WARREN H. LEWIS AND MARGARET R. LEWIS
From Johns Hopkins University and Department of Embryology,
Carnegie Institution of Washington
FOURTEEN FIGURES
Abundant outgrowth of skeletal muscles of chick embryos
can readily be obtained by means of tissue cultures in Locke’s
solution, with or without the addition of other substances.
The characteristic outgrowth can be recognized at a glance
and presents features of unusual interest. That such a highly
differentiated tissue as cross-striated muscle should grow out
so abundantly in Locke’s solution is somewhat surprising.
Harrison 710 noticed in cultures of tadpole tissues in frog
lymph in a few instances, where the explanted myotome was
thin, that the primitive myoblasts differentiated into cross-
striated fibers. He did not find, however, that the myoblasts
grew out into the culture medium. That amphibian embryonic
tissue, where the amount of stored egg yolk supply is consid-
erable should retain the power of differentiation outside the body
agrees in general with what we know in regard to the power of
self-differentiation exhibited by such tissues when they are
transplanted to other parts of the same or different embryos.
It indicates that muscle, or better, premuscle tissue can proceed
along the path or at least a certain portion of its path of differ-
entiation independently of any specific influences from the other
tissues of the embryo. The possibilities of such self-differen-
tiation are already inherent in the cells that are destined to
form muscle in the wide open blastopore stage of the frog.
For, as pointed out by Lewis, pieces of the rim of the blastopore
when transplanted into older embryos continue to differentiate
into muscle, notochord and nervous system.
169
THE AMERICAN JOURNAL OF ANATOMY, VOL. 22, NO. 2
SEPTEMBER, 1917
170 WARREN H. LEWIS AND MARGARET R. LEWIS
Sundwall (712) obtained growth of muscle tissue from the
embryos of guinea pigs 2 em. in length. He found three main
types of cells, (a) elongated spindle forms, (b) polygonal, and
(c) giant cells. He also observed every gradation between these
three types of cells. The elongated spindle forms described by
Sundwall evidently correspond to the isolated fibers and myo-
blasts which are frequently abundant in our cultures. The
polygonal and giant cell forms correspond perhaps to the more
irregular multinuclear pieces of muscle buds that we sometimes
find when the connection between the muscle bud and the ex-
plant becomes broken. Sundwall does not seem to have found
in his cultures the large muscle buds which are so characteristic
of our cultures.
Congdon (15) observed in plasma cultures the outgrowth of
premuscle cells from the limb buds of seven day chick embryos.
The cells were in the form of much elongated spindles. The
outgrowth was rather scanty and not nearly so abundant as
are the spindle shaped myoblasts in our cultures in Locke’s
solution.
Levi (16) has recently described in a few words the fact that
he obtained the outgrowth of striated muscle fibers of chick
embryos in plasma. He gives the impression that the outgrowth
of the skeletal muscle corresponds more or less to that of the
heart muscle with which his paper is more especially concerned.
Previous to this M. R. Lewis (’15) briefly described this out-
growth of skeletal muscle in Locke’s solution in her paper deal-
ing with the rhythmical contractions exhibited by some of the
isolated skeletal muscle fibers found in these cultures.
It is possible that cross striated muscle fibers grow much
better in Locke’s solution than in other media since among the
numerous contributions to tissue culture so little has been said
of cross striated muscle by other observers who have confined
themselves mostly to plasma diluted with water or Locke’s
solution as a culture medium, while we have used Locke’s solu-
tion with or without the addition of other substances. The
outgrowths of muscle in Locke’s solution present such striking
features, and they are so characteristic in shape as well as so
CROSS STRIATED MUSCLE IN TISSUE CULTURES 1g
abundant in quantity that they could not well be overlooked
if present in plasma cultures.
THE EXPLANTED PIECES
The explants consist of small pieces of muscle a millimeter
ov less in diameter taken from the muscles of the back, wing
or leg of chick embryos. of seven to eleven days incubation.
The muscle fibers in the explanted pieces show somewhat vary-
ing degrees of differentiation of the cross-striations. The gen-
eral character of the outgrowth, however, is much the same
from pieces of muscle of the above ages, although no two cultures
are exactly alike.
In the seven day chick the cross striations are but slightly
developed in the myotomic muscles of the back and they are
practically not developed at all in the limb muscles. In the
nine day chick, however, the cross striations are very apparent
in the muscles of both the back and the limbs, especially the
muscles of the upper part of the wing and the leg.
The explanted pieces consist for the most part of a matrix
of mesenchymal cells in which are embedded the young muscle
fibers many of which are cut across at one or both ends. Huber
has recently shown that in the adult rabbit muscle the fibers
vary greatly in length even in the same fasciculus and probably
the same condition holds in the young developing muscles of
the chick embryo. We should expect then that the fibers in
the piece at the time of transplantation would be of various
lengths.
The variations in the size and the length of the fibers in the
explanted pieces would explain in part at least the great differ-
ence in the length and the size of the outgrowing muscles buds.
The medium does not, of course, afford all the necessary sub-
stances for growth. The muscle bud is probably derived for
the most part from the substance of the old muscle fiber, the
medium may furnish some food and the substances derived
from the disintegration of cells within the explanted piece may
also contribute.
AND MARGARET R. LEWIS
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CROSS STRIATED MUSCLE IN TISSUE CULTURES [73
In many of the cultures, owing to extensive migration, from
the explanted piece, of the mesenchymal cells during the first
two days the explanted piece often becomes thinned out so
that one can observe the muscle fibers within it more clearly
than at the time of the first appearance of the muscle buds. In
such cases the direct continuity of the muscle buds with the old
fibers is definitely demonstrated in the living cultures and this
continuity can also be observed after the culture is fixed and
stained. Sections through the explanted piece and the culture
in a plane parallel to the cover slip likewise show this continuity
of the old muscle fibers and the new muscle buds.
THE GENERAL CHARACTER OF THE MUSCLE OUTGROWTHS
The muscle outgrowths, though somewhat varied in details,
have on the whole certain general characteristics that enable
one to readily distinguish them from other tissues which grow
out from the explanted piece (figs. 1, 2, 3, 4, and 5).
The muscle outgrowths occur either in the form of muscle
buds that are continuous with the cut ends of the muscle fibers
or as free fibers which wander out into the medium among the
mesenchyme cells on the under surface of the cover slip. In
most cultures both the attached buds and the free wandering
fibers are found in abundance. The muscle buds vary in size
from short, slender, pointed processes to large flat masses with
many processes at the peripheral end and many nuclei. In
practically all of the cultures the outgrowth of the mesenchymal
cells begins earlier than that of the muscle fibers and forms a
considerable zone of cells about the explanted piece before the
muscle buds appear.
The muscle buds usually begin to appear around the edge of
the explanted piece at the end of the first day or during the
Fig. 1 Muscle from the leg of a seven day chick embryo cultivated in 4
Locke’s solution plus 3 bouillon plus 0.5 per cent dextrose for forty-eight hours.
Osmic acid vapor fixation, Benda stain. The long muscle buds radiate out
from the explanted piece and are easily distinguishable from the mesenchyme
cells. The explanted protoplasmic end of the muscle buds contain many nuclei.
The muscle buds show branches and anastomoses. X 100.
iad
ont
Fig. 2 Somewhat different character of muscle outgrowth from an explanted piece
of the same leg and cultivated in the same way as in figure 1. The enlarged
protoplasmic ends are not so abundant. There are many isolated muscle fibers and
myoblasts among the mesenchyme cells. > 100.
174
CROSS STRIATED MUSCLE IN TISSUE CULTURES 175
second day and do not reach their maximal growth until the
end of the third or fourth day. The buds even at the beginning
of their growth appear to be less differentiated than are the fibers
in the explanted piece from which they grow. This is especially
true in the case of muscle buds from fibers where the cross
striations are well marked, as in the explanted pieces taken
from the older chicks (nine to eleven days).
The bud first appears projecting from the edge of the ex-
planted piece as one or more pointed processes which adhere to
the cover slip. These processes are continually changing in
length and size and slowly advance farther and farther out on
the coverslip, pulling behind them, as it were, a broad thin
expanded mass of muscle cytoplasm that retains its continuity
with the end of one of the muscle fibers within the explanted
piece. As the whole mass creeps out farther, nuclei begin to
appear in the more proximal part of the mass (fig. 5). As the
large flattened protoplasmic mass creeps still farther out on the
cover slip, that part of the bud which connects it with the old
piece in many cases becomes narrower or more slender and is
apparently not so closely attached to the cover slip. The brush
like protoplasmic tips with the slender connecting fibers are well
shown in figure 1. The protoplasmic tips are evidently the
actively migratory part of the bud (figs. 1, 3, 4,5). The proc-
esses are at all times more or less active. They are often Jong
and slender and usually are more numerous at the extreme end
of the bud than along its sides.
As the protoplasmic end migrates farther and farther out on
the cover slip it apparently exerts more or less of a pull on that
part of the bud which connects it with the old piece. It is not
uncommon for the resulting slender part to break in two and for
both ends to rapidly contract, as though the fiber had been
under considerable tension. The entire muscle bud may con-
tract back towards the explanted piece if the protoplasmic end
becomes loosened from the cover slip.
There is a marked tendency for anastomoses and fusion of
muscle buds either directly or by branches. The muscle buds
from neighboring fibers often fuse near the edge of the explant
176 WARREN H. LEWIS AND MARGARET R, LEWIS
CROSS STRIATED MUSCLE IN TISSUE CULTURES sed
and continue to grow out in this manner (figs. 1, 3, 4, 8). Buds
widely separated at their origin often fuse at some distance
from the explanted piece when their direction of outgrowth is
such as to bring them into contact with each other (fig. 3).
The muscle buds very often send off branches of different
sizes, such branches project at various angles and often unite
with other branches or buds. This may result in the formation
of more or less complex networks (figs. 3, 4). In some cases
the anastomoses are probably without direct continuity of the
cytoplasm but in many cases there is undoubted continuity of
the cytoplasm (fig. 8).
There is a very curious resemblance between the outgrowths
of muscle and nerves in the tissue cultures. The formation of
protoplasmic buds with numerous long processes that are con-
tinually changing and the migration of this mass away from the
explanted tissue pulling out the muscle or the nerve fiber present
somewhat similar phenomena. The two differ markedly in one
important respect. The nerve outgrowths are entirely without
nuclei while the muscle fibers contain many nuclei both in the
protoplasmic buds and in the connecting fiber.
Different muscle buds, although they have the same general
character, vary considerably in the more detailed appearances.
Figures 1 and 2 show long slender outgrowths from a piece of the
leg muscle of a seven day chick embryo. The two explanted
pieces were from the same leg and planted in the same medium
(one-half Locke’s plus one-half bouillon plus 0.5 per cent dex-
trose). In figure 1 the ends are rather broad and fan-shaped
while in figure 2 they are narrow or pointed. There are more
anastomoses in the former culture than in the latter. In figure
2 there are to be seen many free fibers with one or more nuclei.
Th se fibers are very slender, pointed at either end and have the
Fig. 3 Muscle outgrowth from an explanted piece of the leg of a nine day
chick embryo cultivated in Locke’s solution plus bouillon plus 0.5 per cent dex-
trose plus 2 per cent distilled water for four days. Osmie acid vapor, iron he-
matoxylin. The muscle buds have not extended out nearly as far as the mesen-
chyme. Several large isolated fibers are to be seen, also anastomoses of muscle
buds. X 100.
178 WARREN H. LEWIS AND MARGARET R. LEWIS
CROSS STRIATED MUSCLE IN TISSUE CULTURES 179
same general direction as the muscle buds from which they
have p obably separated.
The muscle buds ‘rom the explanted pieces of the seven day
chick embryo are much slenderer than those shown in figure 4
from the leg of an eight day chick embryo. The latter culture
was made in Locke’s solution plus a little yolk. Whether the
differences in the growth are the result of the differences in the
media is not clear. They do not seem to depend upon the
differences in the ages of the chicks for we see in figure 3 the
slender type of growth from a nine day chick embryo, somewhat
similar to that from explants from the seven day chick embryo.
It is not uncommon for branches to split off completely from
the outgrowing buds and to wander freely among the mesen-
chyme cells. “uch isolated fibers may have one or two or sey-
eral nuclei. Some seem to come directly from the explanted
piece. The mononuclear and binuclear fibers are usually long
and slender, very pointed at both ends and resemble young
myoblasts. Others are somewhat irregular as in figure 13.
The multinuclear ones vary somewhat in shape but are usually
long and slender as in figure 12. Figures 2, 3, and 4 show vari-
ous types of these free fibers. Some of them represent the entire
peripheral end of a muscle bud and are more or less irregular,
occasionally branched. They all have a cytoplasmic texture
similar to that of the muscle buds and are easily distinguished
from the mesenchyme cells by this as well as by their charac-
teristic shape and by the nuclei.
Occasionally the more proximal part of the muscle bud becomes
spread out into a thin veil-like membrane as in figure 14. Here
two neighboring fibers are thus spread out against the cover
slip and fused together to form an exceedingly thin membrane.
The general appearance of the entire culture was similar to that
shown in figure 4. The nuclei are abundant in this veil-like
membrane.
Fig. 4 Muscle and mesenchyme outgrowth from an explanted piece of the
leg of an eight day chick embryo cultivated in Locke’s solution plus 0.5 per
cent dextrose plus few drops of yolk for two days. The deeply staining muscle
buds and smaller isolated fibers are easily distinguished from the mesenchyme.
Osmic acid vapor, iron hematoxylin. X 100.
CROSS STRIATED MUSCLE IN TISSUE CULTURES 181
Some of the muscle buds seem to consist 0° chains of myo-
blasts which extend far out into the culture. Such buds tend
to break up or give off the individual myoblasts.
The muscle buds do not degenerate in the cultures as a rule
until after the mesenchyme cells.
THE CYTOPLASM
The muscle buds from the eight or nine day chick embryos
that arise from the cut ends of cross striated fibers are with very
rare exceptions entirely devoid of cross striations. Sections
through the explanted piece from a nine day chick embryo show
even after two or three days in vitro well marked cross striations
in most of the muscle fibers. The muscle fibers within the ex-
planted pieces then do not seem to suffer any loss of differ-
entiation. The area of transition between the cross striated
muscle fiber within the explant and the unstriated muscle bud
covers a very short distance in which there is a gradual fading
out of the cross-striations. In one or two instances we have
seen in fixed specimens indications of cross-striations in the out-
growing muscle buds. Such cross-striations are not well marked
and only occupy a small portion of the bud, usually at the edge
of the bud in the part of the fiber connecting the protoplasmic
end with the old fiber in the explanted piece. These cross-
striations were not directly continuous with those in the old
fiber. Rarely also cross-striations are seen in the isolated myo-
blasts but in no cases were they well developed. We are not
prepared to state definitely whether such cross striations are
Fig. 5 Muscle buds with many nuclei from an explanted piece of the leg of
an eight day chick embryo cultivated in Locke’s solution plus bouillon plus 0.5
per cent dextrose plus 1 per cent distilled water for two days. Osmic acid
vapor, iron hematoxylin. X 100.
Fig. 6 Protoplasmic ending of muscle bud showing fine striae, spindles and
processes. Osmic acid vapor, iron hematoxylin. Leg eight day chick embryo,
cultivated in 80 per cent Locke’s solution plus 20 per cent bouillon plus 0.5 per
cent dextrose for two days. X 525.
Fig. 7 Another protoplasmic ending from the same specimen as the above.
Fig. 8 From the same specimen as above showing fusion of two normal
buds.
182 WARREN H. LEWIS AND MARGARET R. LEWIS
due to a redifferentiation or are remnants of the cross striations
of the old fibers which have been carried out into the muscle
bud. In regenerating mammalian muscle fibers Waldeyer has
pictured isolated groups of cross striations in the young muscle
bud which were apparently carried out into the muscle bud and
so do not indicate the beginning of redifferentiation. From
the work of Waldeyer, Volkman, Ziegler and others it is well
known that the regenerating muscle buds In mammals are in
the early stages entirely devoid of cross-striations except for
such instances as quoted above.
The similarity between the muscle buds in tissue cultures
and those pictured for the regeneration of muscle in mammals
indicates that we have here in tissue cultures a process essen-
tially the same so far as the initial stages are concerned.
The cytoplasm in the living cultures shows a very fine striation
which has in general a longitudinal direction. This gives to
the cytoplasm of the muscle bud a very characteristic appear-
ance that distinguishes the muscle buds and the isolated fibers
from other cells of the culture. One gets the impression that
this cytoplasm has a firmer consistency than that of the mesen-
chyme cells. The cytoplasm is also somewhat more refractive
than that of the mesenchyme. These longitudinal striae are
much finer than the so-called sarcostyles or myofibrils seen in
fixed normal muscle. The myofibrils are apparently wanting
in the muscle buds of the tissue cultures and in the early buds
of regenerating muscle.
Cultures fixed in osmic acid show the same characteristic
fine Jongitudinal striations. This is especially well seen in the
expanded ends of the muscle buds (figs. 6, 11).
In some of the fixed preparations it 1s not uncommon to find
in the muscle buds especially in the enlarged ends, spindle-
Fig. 9 Protoplasmic end of muscle bud from eleven day chick embryo cul-
tivated in 90 per cent Locke’s solution plus 10 per cent bouillon plus 0.5 per
cent dextrose for two days.
Figs. 10 and 11 Protoplasmic ends from muscle bud of the wing of an eight
day chick embryo cultivated in Locke’s solution plus 0.5 per cent dextrose for
three days. Figure 11 shows the striae and spindles.
183
CROSS STRIATED MUSCLE IN TISSUE CULTURES 185
shaped bodies. They stain dark with iron hematoxylin and
red with Mallory’s stain. In favorable specimens, these spindles
were seen to fray out in places into fine striae similar to those
composing the cytoplasm (figs. 6, 7, 8, 10, 11). Such spindles
have not been observed in the living buds.
Specimens fixed with acetic acid combinations and especially
with acetic acid vapor give pictures of fibrils and other struc-
tures within the muscle buds, which are not present in the Jiving
cultures. Such methods are of course entirely useless so far
as the study of the optical structure of the cytoplasm is con-
cerned. The fibrils ‘brought out’ by the acetic acid are espe-
cially marked in that part of the muscle bud connecting the
amoeboid end with the explanted piece. This portion of the
muscle bud is evidently under considerable tension as we have
already noted. It is probable that coagulation of the cytoplasm
when in a state of stress or pull takes place in lines parallel to
this stress and hence the formation of the longitudinal fibers.
Under such conditions the fibers brought to view are no indica-
tion whatsoever of their being differentiated structures in the
cytoplasm.
The mitochondria are especially abundant in the muscle buds
and are arranged longitudinally between the fine longitudinal
striae. They are smaller than those in the mesenchyme cells
and in the healthy fibers do not show the same irregular arrange-
ment. It is rather difficult to make them out in the living buds.
With Janus green, however, they usually appear as strings of
minute granules of varying lengths and sometimes as long
threads which seem to taper off at either end to the limits of
visibility. The mitochondria are best seen in the enlarged
protoplasmic end of the buds and undoubtedly contribute to
the appearance of longitudinal striation.
Fig. 12 Isolated muscle fiber from the same culture as the above.
Fig. 13 Isolated myoblast from the cultures from the wing of an eight day
chick embryo cultivated two days in 80 per cent Locke’s solution plus 20 per
cent bouillon; plus 5 per cent dextrose. 525.
Fig. 14 Veil-like spreading out of the stem of a muscle bud from a two day
culture of the muscle from the wing of an eight day chick. Locke’s solution p!us
few drops yolk plus 0.5 per cent dextrose. 455.
THE AMERICAN JOURNAL OF ANATOMY, VOL. 22, NO. 2
186 WARREN H. LEWIS AND MARGARET R. LEWIS
Aside from the mitochondrial inclusions the cytoplasm con-
tains varying numbers of neutral red granules. These are
minute and not very abundant, and are usually situated in the
neighborhood of the nuclei.
THE NUCLEI
The nuclei appear in the young muscle buds soon after the
protoplasmic ends begin to project from the explanted piece.
They gradually increase in number as the bud increases in length
and size. There is usually a Jarge group of nuclei in the ex-
panded end. They occupy the more proximal part of this
expansion while the more distal part is usually free from nuclei.
The narrow part of the muscle bud connecting the protoplasmic
end with the explanted piece has a varying number of nuclei
scattered along it. The isolated myoblasts and fibers contain
varying numbers of nuclei from one to many. We have exam-
ined repeatedly both living and fixed cultures for indications
of nuclear division but only in a few instances have we seen
mitotic divisions and those occurred in the mononuclear myo-
blasts that were free in the culture. When the nuclei of the
muscle buds were studied the condition of the mesenchyme in re-
gard to the frequency of cell division was usually noted and it was
not uncommon to see three or four mitotic figures in the mesen-
chyme cells in the neighborhood of the muscle buds in one field
of the microscope. In spite of the fact that we have very little
direct evidence of nuclear division in the muscle buds it seems
probable that nuclear division does take place. Some muscle
buds have thirty or forty or more nuclei and they must either
have arisen by division from a few or more that came out from
the old piece or have all migrated out from the old fiber as the
muscle bud grew out from it on to the cover slip. The indirect
evidence in favor of nuclear division is revealed through the
staining of fixed specimens. In such specimens, stained either
with iron hematoxylin or with Ehrlich’s hematoxylin and eosin,
it is seen that the nuclei vary considerably in their staining
teaction. Some are darkly stained, others rather lightly, and
CROSS STRIATED MUSCLE IN TISSUE CULTURES 187
this holds even among the nuclei that lie side by side in the same
group. We have often noticed similar differences among the
nuclei of mesenchyme cells when active mitotic division is taking
place. In fact everyone who has studied embryonic material
has probably noted such differences in the staining reactions
of nuclei. It is especially well marked, for example, in the cells
of the neural tubes of young amphibian embryos where active
mitotic division is taking place. We have been able to demon-
strate in our cultures that the nuclei of the young daughter
cells of the mesenchyme always stain deeper than the nuclei
of the resting cell. This ability of the daughter nuclei to stain
more deeply lasts for an hour or two after the mitotic division.
If mitosis were taking place to any great extent in the muscle
buds we should probably have observed it especially in the ex-
panded end of the bud. Yet here as well as elsewhere in the
muscle bud the stainable differences in the nuclei are found in
abundance. Of course it may be that the nuclei undergo mitotic
division in the old piece out of range of direct observation in the
living. On the other hand, there is, of course, the possibility
of direct division. Direct division seems to be extremely rare
in our cultures and Macklin, after an extensive series of obser-
vations, was able to observe but one case of direct division of
the nucleus in the mesenchyme celJs, and that without division
of the cytoplasm. We have not observed direct division of
muscle nuclei and have no data on the staining reaction of nuclei
after direct division.
The observations on the nuclei of muscle buds in the living
are much more difficult than are those upon the nuclei of the
mesenchymal cells and for the present at Jeast many questions
in regard to the origin of these nuclei must be left unsettled. It
is often stated that direct as well as indirect division of the nuclei
takes place in the regeneration of muscle in amphibia and mam-
mals. Such statements are based not on direct observation of
the living but on fixed preparations. It is evident from our
studies on the living cells in tissue cultures that such observa-
tions on fixed and stained material in regard to direct division
are no indication of what actually occurs in the living. Many
188 WARREN H. LEWIS AND MARGARET R. LEWIS
fixed specimens seem to indicate that the nuclei show all stages
in the process of direct division while observations on similar
cultures in the living fail to give evidence of a direct division.
DISCUSSION
The muscle buds from the explanted pieces of the older em-
bryos (nine to eleven days), which arise from the cut ends of
the cross-striated fibers, appear to be less differentiated or more
embryonic in type than normal muscle fibers of the same age.
A process of dedifferentiation has evidently occurred in the for-
mation of these muscle buds from the old fibers. Is this a true
reversibility or merely a breakdown with elimination or absorp-
tion of some of the more differentiated parts of the cytoplasm?
Such unstriated buds are still capable of contraction and when
portions of them become separated off they may undergo
rhythmical contractions. It is then not necessarily loss of
function which determined this dedifferentiation. Contractions
occur however rather rarely. The fibers in the old piece are
of course entirely severed from all nervous connections and there
is no indication that they contract yet they retain their cross-
striations.
This process of dedifferentiation or a return to a more embryonic
condition probably underlies all types of regeneration. We
doubt if there is ever-any regeneration of differentiated tissue
without a preliminary return of the cells involved to a more
embryonic condition. In regeneration this preliminary stage
of dedifferentiation prepares the way for growth and redifferen-
tiation. The dedifferentiation in regeneration does not neces-
sarily proceed to the extent in which the cells of the various
tissues return to a common embryonic type, such as Champy
maintains happens to practically all cells in tissue cultures.
As we have seen this process of dedifferentiation does not pro-
ceed in our cultures to such an extent as to render the muscle
cells indistinguishable from other types of cells. Prolonged
cultivation might result in a return to a still more embryonic
type of the outgrowing muscle tissue.
CROSS STRIATED MUSCLE IN TISSUE CULTURES 189
Champy, in a series of articles, has maintained that most of
the cells in the body dedifferentiate in tissue cultures. They re-
turn, he claims, to a completely indifferent type of cell that no
longer shows the imprint of its origin. In explants from late
fetal stages he finds that cells of the kidney tubules, of the thyroid,
of the parotid andof the submaxillary glands, of the smooth
muscle, of the mesenchyme, etc. dedifferentiate into an indifferent
embryonic type indistinguishable from each other. This dediffer-
entiation, he claims, is associated with the phenomena of cell
division.
The rapidity of dedifferentiation is a function of the rapid-
ity of the cell-division. Furthermore, according to Champy,
all cells differentiated for a special function lose or tend to lose
during mitosis, their characteristic function. In the animal
organism they recover immediately after the telephase, since
they are subject to the same functional excitation as before
division. In the body, function does not maintain the differ-
entiation but the function provokes and creates anew the dif-
ferentiation after each mitosis. Champy’s ideas are based in
part on a law formulated by Prenant that a cell during mitosis
does not secrete. Among the tissues which do not dedifferen-
tiate he finds the liver cells of the rabbit near term, the true
gray substance of the central nervous system and striated
muscle. Such tissues he finds do not grow out into his cultures
and he reasons that since they do not grow and vegetate they
are not susceptible of dedifferentiation. Maximow, on the
other hand, takes exception to Champy. He finds that fibro-
blasts continue indefinitely as such through many generations
of the culture and for this reason he calls them ‘immortal’
cells. Maximow also finds that the endothelial cells of blood
vessels and of lymphatics as well as the mesothelial cells lining
the serous cavities change into fibroblasts and become indis-
tinguishable from those of connective tissue origin. This de-
differentiation is according to Maximow only apparent since he
considers the endothelium of blood vessels and lymphatics and
the serosa but flattened-out fibroblasts.
190 WARREN H. LEWIS AND MARGARET R. LEWIS
The foregoing conclusions of Champy and the less general
conclusions of Maximow in regard to the fate of endothelium
and mesothelium are certainly in need of further substantiation.
During the process of regeneration, in vertebrates at least, the
dedifferentiation never proceeds to an indifferent stage; muscle
is regenerated from muscle, nervous tissue from nervous system,
bone or cartilage from bone or cartilage, ectoderm from ecto-
derm, ete.
In prolonged cultivation by means of frequent retransplanta-
tion of the culture such as was carried on first by Carrel, the fibro-
blasts seem to be the only cells which survive so that finally they
are obtained in pure cultures.’ It is probably that both Champy
and Maximow failed to realize that it is a question of the sur-
vival of the fittest and not complete dedifferentiation which is
responsible for the appearance in cultures that have been carried
on for many generations of but a single type of cell. Then too
we must bear in mind the fact that even in the early stages of
cultivation there is often great difficulty in distinguishing the
various types of cells.
We are more especially concerned in this preliminary and es-
sential process of dedifferentiation. That it should take place
in a minute isolated piece of muscle outside the body, in an
artificial medium, is of great significance. It makes possible
an analysis of the process in a way that was not realizable in the
living organism. Attempts to get growth and regeneration
from small pieces of muscle (one-half to one centimeter in diam-
eter) in vivo have failed. Such pieces even when transplanted
into muscle itself always degenerate (Volkman). It may be
that pieces as small as those used in tissue cultures would have
continued to live in vivo.
The nature of the changes in the organization of the cells of
tissue cultures undoubtedly depends in part on the tissue ex-
planted, in part on the age of the embryos or animal employed
and in part on the culture medium and the peculiar conditions
to which the cultures are subjected. Tissues of late fetal stages
or of stages subsequent to birth in which differentiation is com-
plete could remain either stationary or dedifferentiate, while
CROSS STRIATED MUSCLE IN TISSUE CULTURES 191
tissues of early embryonic stages might continue to differentiate,
or remain stationary or dedifferentiate. In either case, patho-
logical changes and degeneration may supervene. We know
that the anlage of many tissues of amphibian embryos (central
nervous system, the eye, otic vesicle, notochord, voluntary
muscle, heart, etc.), when transplanted into strange environ-
ment of the same or another embryo will continue to differen-
tiate. There is a period during which many young embryonic
tissues are self-differentiating. It is not surprising then that
Harrison should have obtained an outgrowth of the axis cylin-
ders from young nerve cells and a differentiation of cross-striated
muscle from young embryonic myoblasts in tissue cultures.
On the other hand, it is perfectly evident that in older embryos
(chick embryos of nine days, for example) cross-striated muscle
as it grows out into the culture loses its cross-striations and as-
sumes a more embryonic condition. The portion of the fiber
which remains in the explanted piece retains, however, its cross-
striations.
The muscle buds found in tissue cultures resemble in many
ways the early stages of the regeneration of muscle in the higher
mammals after injury or rupture of the muscle fibers as described
by Waldeyer (’63) and Volkmann (’83) and Ziegler (98). In
mammals the buds which grow out from the cut ends of the:
fibers are more or less homogeneous and unstriated. There are
often lateral buds as well. These buds elongate and extend be-
tween the connective tissue cells filling in the wound. Such
buds are crowded with nuclei which are supposed to increase
in number for the most part by direct division. Mitoses are
also found. There are also found free myoblasts, long spindle
cells with one or more nuclei, which come from the old piece.
There is also a disappearance of the cross-striations in the old
fibers near the cut ends. The process of regeneration is slow,
extending over weeks. A redifferentiation occurs in these buds
with the formation of longitudina] and cross-striations so that
finally they come to resemble the old fibers. The free myo-
blasts also differentiate in a manner similar to that of embryonic
myoblasts.
192 WARREN H. LEWIS AND MARGARET R. LEWIS
The experiments on the regeneration of muscle in amphibia
also show that there is a return first to an embryonic type of
muscle cell followed by a redifferentiation in a manner similar
to the differentiation of embryonic cells. These myoblasts
come from the injured muscle fibers (Fraisse, Barfurth and
Towle). According to Towle, the outer bundles of the cut
muscle disintegrate leaving nuclei surrounded by cytoplasm.
The nuclei increase in number by amitosis. Some of the cells
thus formed later divide by mitosis and from them are formed new
muscle fibers. The inner bundles of the muscle do not disin-
tegrate but split longitudinally into myoblasts which later dif-
ferentiate into muscle. Barfurth finds that in the very young
larvae of Siredon, terminal and lateral buds grow from the in-
jured fibers. The outgrowths contain nuclei and form sarco-
blasts (myoblasts) and these differentiate into muscle fibers in
the same way as do the myoblasts of the normal embryo. In
the older larvae of the frog and in mature animals, there occurs a
degeneration of the muscle with the accumulation of nuclei and
the formation of giant cells. He also finds that there is a split-
ting of old fibers into myoblasts as well as sarcoblast-like out-
growths which form myoblasts which later become new muscle
fibers.
The initia] stages in the process of regeneration of muscle
in mammals and amphibia are in many respects very much like
the behavior of muscle in our cultures. In both there is (1) a
formation of young myoblasts, a return to a more embryonic
condition; (2) the formation of protoplasmic buds which grow
out from the ends of the old fibers. Such buds contain many
nuclei and lack cross-striations.
The factors involved in the formation of these muscle buds
are probably the same in the tissue cultures and in regeneration
and consequently are common to each. We can eliminate at
the outset then various possible factors that are present where
muscle buds are formed in the regeneration of muscle in the
experimental animals, such as the influence of the nervous sys-
tem, of substances brought by the blood or body fluids or of
other influences that might come from the organism itself.
CROSS STRIATED MUSCLE IN TISSUE CULTURES 193
The formation of the muscle buds seems to be inherent in the
muscle fiber itself and becomes manifested when the fiber is cut
across or is injured. The peculiar form which they take as long
narrow fibers is to be attributed to the specific complex of mate-
rials which compose the muscle substante and to the dynamic
processes which occur there.
Although the initial stages are much the same in cultures and
in regeneration, it is not to be expected even after prolonged
cultivation in vitro there will be a redifferentiation of the muscle
buds. Especially will this be true, if, as Morgan suggests, the
same factors which affect the normal growth and differentiation
of the embryo affect in the same way the regeneration of a part.
In the healing of wounds a similar process of dedifferentiation
followed by a redifferentiation is involved.
The anastomoses between muscle buds suggests that in the
normal muscle there may yet be found a syncytial like condition
even in the adult. It lends some support to Huber’s suggestion
that muscle may be syncytial in character which suggestion he
makes in spite of the fact that he has succeeded in isolating
fibers of various lengths. On the other hand, it may be that the
peculiar conditions found in tissue cultures produce conditions
not normally present. We have in the past often observed
anastomoses of nerve axones in cultures of sympathetic fibers.
Even if such phenomena are the result of peculiarities of cul-
tures that are not present in the living organism, they serve to
show us at least some of the potentialities of muscle and nerve
protoplasm.
194 WARREN H. LEWIS AND MARGARET R. LEWIS
BIBLIOGRAPHY
Apam1 1908 Principles of Pathology, vol. 1.
CarreL, A. 1914 Present condition of a strain of connective tissue 28 months
old. Jour. Expt. Med., vol. 20, 1914.
Cuampy, ©. 1912 Sur les phénomenes cytologiques qui s’observent dans les
tissues cultivés en dehors de |’organisme. (tissue epitheliaux et glandu-
laires). Comptes rendus de la Soc. d. Biol., T. 72, p. 987.
1913 La dedifférentiation des tissues cultives en dehors de l’or-
ganisme. Bibliogr. Anat., T. 22.
1914 Quelques resultets de la méthode de culture des tissues. I.
Généralitiés. II. Le muscle tissue. Arch. Zool. Exper. et Gén.,
aaS:
1914 Notes de biologie cytologique. Quelques resultats de la
méthode de culture de tissues. III. Le rein. Arch. de Zool. Exp.,
ee 54:
Conapon, E. D. 1915 The identification of tissues in artificial cultures. Anat.
Rec., vol. 9.
Fraisse, P. 1885 Die Regeneration von Geweben und Organen bei den Weibel-
thieren, besonders bei Amphibien und Reptilien. Berlin und Kassel.
- Harrison, R. G. 1910 The outgrowth of the nerve fiber as a mode of proto-
plasmic movement. Jour. Exp. Zool., vol. 9.
Huser, G. C. 1916 On the form and arrangement in fasciculi of striated vol-
untary muscle fibers. Anat. Rec., vol. 11.
Levi, G. 1916 Migrazione di elementi specifici differenziati in colture di
miocardio e di muscoli scheletrici. Archivio per le scienze Medichi.,
Ann. 40.
Lewis, M. R. 1915 Rhythmical contractions of the skeletal muscle tissue ob-
served in tissue cultures. Am. Jour. Physiol., vol. 38.
Mackuin, C. C. 1916 Binucleate cells in tissue cultures. Contributions to
Embryology, No. 13. Publication 224, of the Carnegie Institution of
Washington.
Maximow, A. A. 1916 The cultivation of connective tissue of adult mammals
in vitro. Arch. Russes d’Anat., d’Hist. et d’Embry., T. 1.
Moraan, T. H. 1901 Regeneration.
SunpwWatL, J. 1912 Tissue proliferation in plasma medium. Bull. U. 8. Hyg.
Lab. and Mar. Hosp., vol. 81.
Tower, E. W. 1901 On muscle regeneration in the limbs of Plethedon. Biol.
Bull., vol. 2.
VoLKMANN, R. 1893 Ueber die Regeneration des quergestreiften Muskelge-
weckes bein Menschen und Siugethier. Beitrige zur path. Anat. u.
Path. Bdea b2:
WaupeEyeR, W. 1865 Ueber die Verinderungen der quergestreiften Muskeln
bei der Entziindung und den Typhusprozess sowie tiber die Regen-
eration derselben nach Substanzdefecten. Arch. fiir Path. Anat.,
Bd. 34.
ZIEGLER, E. 1898 Lehrbuch der allgemeinen Pathologie und. d. Path. Anat..
Bale
AUTHOR'S ABSTRACTS OF THIS PAPER IS-
SUED BY THE BIBLIOGRAPHIC SERVICE
STUDIES ON THE MAMMARY GLAND
Il. THE FETAL DEVELOPMENT OF THE MAMMARY GLAND IN THE
FEMALE ALBINO RAT
J. A. MYERS
Institute of Anatomy, University of Minnesota
TWELVE FIGURES
Henneberg (00) made a careful study of the development of
the mammary glands in the albino rat from the earliest appear-
ance of the glands through the conditions found in sixteen day
fetuses. Also the postnatal (birth to ten weeks) development
of these glands has been investigated (Myers, 716). Heretofore
the developmental conditions between sixteen day fetuses and
newborn rats have presented a gap in our knowledge of the
mammary glands. The object of the present investigation is to
fill up this gap, thus completing the history of the mammary
glands in the albino rat (Mus norvegicus albinus) to ten weeks
after birth. An abstract of the results has already been pub-
lished (Myers, 17).
: LITERATURE
No attempt is made to review all the literature pertaining
to the development of the mammary gland, which is thoroughly
discussed in the works of Bonnet (’97), Brouha (’05), Bresslau
(10) and Schil (12). Henneberg’s work (’00) in the early de-
velopment of the mammary glands in the albino rat is here
briefly reviewed, however, since the earlier stages must be
kept in mind to make clear their relations with the later foetal
stages described in the present paper.
Henneberg (’00) found in an albino rat embryo of eleven
days, in the region of the dorsal limiting furrow (on only one
side), some cubical cells in a single layer representing the anlage
of the mammary streak. In an embryo of twelve days a mam-
195
196 J. A. MYERS
mary streak is present on each side. Hach streak consists of a
single layer of cubical epithelium. The breadth of the streak
has increased and now extends from a few cells dorsal to the
dorsal limiting furrow ventrally to cover nearly half of the
parietal zone. Its cephalic and caudal ends blend with the
cubical epithelium of the limb anlages.
At twelve days and thirteen hours, the cells of the mammary
streak are larger and in the region of the dorsal limiting furrow a
second layer of cells is beginning to appear superficial to the
cubical cells. Immediately beneath the mammary streak the
mesenchymal cells have condensed. The mammary streak
shows two distinct cell layers in embryos of thirteen days and
one hour. The superficial layer—stratum corneum—consists of
flat cells with oval nuclei with their long axes parallel to the
surface. The deep layer—stratum mucosum—is composed of
large round or cubical to cylindrical cells with oblong nuclei.
The streak is separated from the mesenchyma by a distinct light
line—the basement membrane.
Henneberg found the first appearance of the mammary line
in a rat embryo of thirteen days and fourteen hours. At this
stage it is produced by a thickening of parts of the mammary
streak. In some places a part of the mammary streak is con-
verted into the mammary line by the appearance of a third layer
of round cells between the superficial and deep layers. In other
places the cells have slightly thickened thus producing the first
appearance of the mammary line without the addition of a third
layer. In other embryos of the same age the mammary line
in the thoracic region is three to four layers of cells thick and its
greatest breadth shows twelve to fourteen layers of cells. It dis-
appears a short distance cephalad to the anterior extremity.
In the inguinal region the line is still very indistinct and requires
special technique for its study. In some embryos a complete
interruption exists between the region of the future thoracic
glands and the-adbominal gland. ‘This is the first intimation
of the future interspace between the glands of the thoracic
region and those of the abdominal and inguinal regions. From
this stage, Henneberg designated the cephalic part of the lne
STUDIES ON THE MAMMARY GLAND 197
as the pectoral portion and the caudal part as the abdominal
portion.
In rat embryos of fourteen days Henneberg found that the
cephalic end of the mammary line has been transformed into a
structure about the shape of a biconvex lens. This is the earliest
appearance of the first pectoral mammary hillock. In other
embryos of the same age the second and third pectoral and the
abdominal hillocks are beginning to appear. The greater con-
vexity of each hillock lies embedded in the mesenchyma. The
remaining parts of the mammary streak and line represented
by the space between the hillocks are beginning to atrophy.
At this stage the mammary line for the inguinal glands resembles
in structure the line for the pectoral and abdominal glands in the
thirteen day and fourteen hour stage.
Henneberg found in fifteen day rat embryos that the mammary
gland anlages are no longer elevated above the surface but that
their deep surfaces have pressed deeper into the mesenchyma
thus presenting the ‘mammary point’ stage. At this stage the
inguinal glands are still somewhat retarded in their development.
At sixteen days Henneberg states that the mammary gland
-anlages correspond to the club-shaped stage which Rein (’82)
found in rabbit embryos. Henneberg did not investigate the
later stages in the rat.
MATERIAL AND TECHNIQUE
The fetuses for the present work were collected in the follow-
ing manner. Adult males and females were placed in the same
cage from six o’clock in the evening until six o’clock in the
morning. As found by Danforth (16) in case of mice, better
results were obtained when the females were placed in the cage
which the males occupy permanently. The females were then
returned to their respective cages. In all cases of pregnancy
semination was dated at the ninth hour after the females were
placed in the cages with the males. The possibility of error in
the age of the fetuses is plainly obvious. However, the error
could only be a matter of a few hours. Sobotta and Burck-
hard (’11) estimated that spermatozoa of the albino rat do not
198 J. A. MYERS
live more than nine or ten hours in the reproductive tract of the
female.
During 1914-1915 a large number of observations were made
on females with the hope of finding a definite way of knowing
just when the animals is in heat or when copulation has taken
place. No definite gelatinous plug was found closing the va-
ginal orifice after copulation as Sobotta (’95) observed in white
mice. A yellow and somewhat viscid vaginal secretion appears
at rather regular intervals. This: secretion usually makes its
first appearance shortly after the opening of the vagina which
occurs about the eighth week. In young females it occurs
thereafter at quite irregular intervals but later it may be seen
about every fifth to eighth day. No definite relation has yet
been established between the appearance of the vaginal secre-
tion and the time of insemination. However, it was noticed
that many of the females became pregnant while the secretion
was present. The origin of the vaginal secretion and its relation
to ovulation is still being studied with the hope of obtaining
definite knowledge as to the time of ovulation in the white rat.
Some of the fetuses were fixed in Zenker’s fluid, others in 10
per cent formalin. In the earlier (fifteen day and nine hours,
sixteen day and twelve hours, and seventeen day and two
hours) stages several fetuses were cut for each stage described
while in the later (eighteen days and nine hours, nineteen days
and six hours, and twenty days and six hours) stages only one
fetus was entirely sectioned and merely the skin containing the
mammary glands from several other individuals was sectioned.
The mammary glands of other fetuses were studied macroscopi-
cally. In all 30 individuals were examined. A part of the ma-
terial was cut at 5 uw or 7 w and stained with iron hematoxylin;
the remainder was cut at 10 « and stained with alum hematoxylin
and eosin or with Mallory’s connective tissue stain. Weigert’s
elastic tissue stain was also applied to some of the fetuses of the
latest stages. For a study of the varieties of white blood cor-
puscles Dominici’s combination stain was used.
A few dissections and observations proved that in the late fetal
stages the sex could be determined by the relative ano-genital
STUDIES ON THE MAMMARY GLAND 199
distance as described by Jackson (’12) in determining the sex
of the newborn. In the earlier fetal stages the sex was deter-
mined by studying the developing reproductive organs.
The wax reconstructions were made according to Born’s
method.
OBSERVATIONS
Henneberg states that in fifteen day and fourteen hour em-
bryos the six pairs of mammary glands occupy their definitive
positions. Since Henneberg made only a macroscopic study of
the glands at this stage, a further account is here given of the
condition found in embryos of nearly the same age.
Fifteen days. On the surface of the skin at this stage (fif-
teen days and nine hours) is a small eminence (fig. 7) over each
developing gland. Such eminences are very prominent in fresh
preparations. A cross section through a gland (fig. 1) shows
that the epidermis in the neighborhood of the gland is composed
of only two layers, a superficial layer (periderm) of flattened
cells with their long axes parallel to the surface, and a deeper
layer (stratum germinativum or Malpighian layer) of round or
cubical cells. The nuclei of the latter layers are located toward
the free end of the cells. The basal ends of the cells have a
quite clear appearance and rest on a definite basement membrane
(fig. 1).
The basement membrane dips down into the underlying mesen-
chyma to surround the spheroidal mass of epithelial cells form-
ing the gland anlage. Likewise the stratum germinativum of the
epidermis passes deep around the same circular mass of cells and
forms the basal layer of the mass. The cells of the spheroidal
mass are differentiated and arranged so that they possess a
characteristic appearance. The cells of the basal layer appear
much more elongated than those in the stratum germinativum
of the adjacent epidermis. The cells occupying the center are
irregular in shape and closely packed.
Superficially the gland anlage projects somewhat producing
the eminence visible from the surface. Around its deep surface
the mesenchyma is condensed. The mesenchymal cells lying
MYERS
A.
J.
STUDIES ON THE MAMMARY GLAND 201
nearest the developing mammary gland are somewhat elongated
and arranged in two or three very regular layers concentrically
placed (fig. 1). Outside of the concentric layers, the condensed
mesenchymal cells seem to have no definite arrangement. In
the condensed mesenchyma is seen an occasional small blood
vessel containing nucleated red blood corpuscles.
Wax reconstructions (fig. 10) show that the differentiated
mass of cells which appears circular in cross section, forms an
oblong ellipsoidal body which is attached to the epidermis by a
very short, constricted neck (nk).
Sixteen days. In fetuses of sixteen days and twelve hours the
mammary eminences still appear on the surface of the skin as
slightly elevated areas which in fresh preparations have a
somewhat lighter appearance than the surrounding tissue.
In microscopic sections the epidermis presents the two distinct
layers of cells found in the preceding stage. In addition an
intermediate layer of cells has appeared in some parts of the
skin. In some places the epidermis is slightly thickened to form
hair anlages, but in no case were such anlages observed in the
epidermis adjacent to the mammary gland anlages. The so-
called basement membrane appears as a homogeneous band im-
mediately below the stratum germinativum. Just beneath the
basement membrane the mesenchymal cells are densely placed
thus forming a fairly definite layer. Immediately beneath this
layer the mesenchymal cells are less numerous and apparently
have no regular arrangement. Mitotic figures are very com-
Fig. 1 Drawing of a section through the right second thoracic mammary
gland region of an albino rat fetus of fifteen days and nine hours. X 300.
Zenker’s fixation; hematoxylin-eosin stain. Drawn with the aid of a camera
lucida. b.m., basement membrane; c.m., condensed mesenchyma; e.s., eminence
(mammary hillock) on surface of skin produced by mammary gland anlage;
m., loose, irregularly arranged mesenchyma; m.a., mammary gland anlage; p.,
periderm; s.g., stratum germinativum.
Fig. 2. Drawing of a section through the left second thoracic developing
mammary gland of a female albino rat fetus of eighteen days and nine hours.
300. Zenker’s fixation; hematoxylin-eosin stain. Drawn with the aid of a
camera lucida. b.m., basement membrane; c.m., condensed mesenchyma; 7.p.,
early appearance of mammary pit; p.d., deep portion of mammary gland anlage
(primary duct); s.m.a., superficial part of mammary anlage, becoming cornified.
THE AMERICAN JOURNAL OF ANATOMY, VOL. 22, NO. 2
202 J. A. MYERS
mon in the mesenchyma immediately surrounding the gland.
An occasional small blood vessel is seen coursing toward the
mammary gland area.
The mammary gland anlages show about the same stage of
development as in the preceding stage. A study of all six pairs
shows that the inguinal mammary glands are slightly behind
the others in their stage of development.
Seventeen days. At seventeen days and two hours the emi-
nences described in the previous stages have disappeared. The
gland areas instead appear as slight depressions or pits on the
surface of the skin. These mammary pits represent the point
of ingrowth of the epithelium. The epidermis is slightly thicker
than in the preceding stage and in the regions of the mammary
glands presents a very definite basement membrane. The gland
anlages now measure only about 0.05 mm. in length.
Eighteen days. Fresh preparations, sections, and wax re-
constructions from fetuses of eighteen days and nine hours show
a definite mammary pit on the surface of the epidermis over each
future nipple area (figs. 2 and 8, n.p.). In cross section the
stratum germinativum is now depressed so as to form a shallow
funnel-shaped outline. The mouth of the funnel is directed
toward the surface and is partly filled with epithelial cells which
show traces of cornification and desquamation. Intercellular
vacuoles are also being formed. The outlet of the funnel ex-
tends into the corium and becomes continuous with the anlage
of the primary mammary duct.
At this stage the gland anlage, which in the earlier stages was
an oblong, ellipsoidal mass of epithelial cells, has increased in
length. Its deep part now becomes the anlage of the primary
duct, while its superficial portion is undergoing vacuolization,
cornification, and desquamation, thus forming the pit superficial
to the primary duct. The end of the primary duct anlage
directly beneath the surface pit is attached to the epidermis and
throughout this paper will be designated as the attached end.
The opposite end of the anlage is unattached and throughout
this paper will be known as the free end. The stratum germi-
nativum of the adjacent epidermis continues over the mam-
mary anlage as its future primary peripheral layer of cells. The
STUDIES ON THE MAMMARY GLAND 203
primary duct anlage is roughly L-shaped with its attached end
perpendicular and its free end parallel to the surface (figs. 2
and 8). The anlage in elongating has pushed ahead of it the
above mentioned layers of condensed mesenchyma representing
the corium and tela subcutanea. These layers now completely
surround the free part of the anlage. In the first thoracic gland
the free end of the anlage is directed cephalad. In the second
inguinal gland, the free end points caudad. Likewise the free
end of each of the remaining ducts is directed toward the position
which the future duct and its branches will occupy.
The anlages of the ducts are longer than in the seventeen day
and two hour stage. In one of the first thoracic glands of one
fetus and in one of the abdominal glands of another fetus the
primary duct presents two secondary ducts (fig. 17, s.d.). All
other glands observed at this stage possess a single undivided
primary duct.
When seen in cross section at this stage, the primary duct of
most of the glands possesses a basal layer of cuboidal cells with
large oval nuclei. The basal ends of the cells rest on a some-
what indistinct basement membrane while the opposite ends are
directed toward the center of the duct. The center of the duct
is filled with cells of irregular shape. Somewhat nearer the free
than the attached end of some of the ducts the cells occupying
the center of the duct show a tendency toward separation from
each other. In other ducts some of the central cells have en-
tirely separated, thus producing small cavities or lacunae, the
first appearance of a very indefinite lumen (fig. 4). Such a
condition obtains in many of the thoracic and abdominal glands
examined, but is very rare in the inguinal glands of this stage.
It is interesting to note that in the thoracic and abdominal
glands which have already developed secondary ducts, only one
of these ducts shows a slight indication of a lumen. The mes-
enchymal cells of the corium and tela subcutanea are somewhat
condensed around the ducts. Those nearest the ducts are
much elongated and are concentrically arranged.
In one abdominal gland about half way between the outlet
and mouth of the funnel the cells of the stratum germinativum
have slightly elongated thus forming a low ridge which projects
204 J. A. MYERS
into the subjacent corium. The ridge extends entirely around
the funnel and is the anlage of the epithelial hood, which was
described in the postnatal stages of the albino rat (Myers 716).
Nineteen days. ‘The funnel-shaped epithelial area correspond-
ing to the mammary pit at nineteen days and six hours con-
tains some cornified epithelium. This is apparently being cast
off by the process of desquamation, thus deepening the mam-
mary pit superficial to the attached primary duct.
The primary mammary ducts have made a rapid growth and
present secondary ducts in all glands, while in most glands
examined the secondary ducts present tertiary ducts. The two
inguinal glands present lumina in about the same stage of de-
velopment as was described in the thoracic and abdominal
glands in the eighteen day and nine hour stage. The rudi-
mentary lumina in all glands are slightly further developed
toward the free ends of the ducts but are by no means confined
to the free ends. Many of the cells near the developing lumina
are undergoing mitotic divisions. There is no pyknosis or other
evidence of cell degeneration.
The anlage of the epithelial hood is composed of elongated
cells of the stratum germinativum, but a second layer of cells deep
to the layer described as forming a low ridge in the preceding
stage is beginning to appear. The ridge now projects deeper
into the subjacent corium. Numerous mitotic figures are seen
in the epithelial cells in the region of the free edge of the hood.
The developing hair follicles have grown more deeply into the
corium than those described in a preceding stage. Ordinarily
the follicles are located a considerable distance from the mam-
mary pits. No follicles were observed in the mammary pits. .
Twenty days. At twenty days and six hours well defined mam-
mary pits in the epidermis represent (as in the preceding stage)
the regions of the mammary glands. Wax reconstructions,
however, show that at the bottom of each pit there is a rounded
elevated portion of the epidermis (fig. 9, n.a.). This elevated
part is the anlage of the nipple. In the preceding stage as noted
the depression or funnel was partly filled with cells, which be-
came cornified as age advanced, thus giving the integument
STUDIES ON THE MAMMARY GLAND 205
over the mammary glands a thickened appearance. Later the
cornified cells were cast out and thus the funnel corresponding
to the mammary pit was deepened. The anlage of the nipple
in the present stage seems to have pushed from the bottom of the
mammary pit toward the surface leaving a surrounding furrow or
sulcus (figs. 3 and 9, s.). The superficial part of the epidermis
over the nipple anlage now appears no thicker than that in
adjacent regions.
The anlage of the epithelial hood has grown more deeply
into the corlum now encroaching upon the tela subcutanea.
Cornified epithelial cells occupy the space between the inner and
outer surfaces of the hood.
When the stratum germinativum of the epidermis is traced
toward the region of the mammary gland it is seem to pass
deeply and form the outer surface of the epithelial hood. It then
covers the free edge of the hood and turning back forms the
inner surface of the hood. Next it covers the deep surface of
the nipple anlage. Throughout its extent in the mammary
region the cells of the stratum germinativum rest on a base-
ment membrane (fig. 3).
The corium within the epithelial hood is composed of con-
nective tissue cells the processes of which take a deep blue stain
when treated with Mallory’s connective tissue stain. Small
blood vessels and nerves are also included. From the surface
of the nipple anlage the primary duct is seen coursing through
the corium in the center of the hood on its way tothe subcutaneous
tela where it turns at right angles after which it lies parallel
with the surface of the integument. Soon after reaching the
subcutaneous tela and turning at right angles the duct divides
into secondary ducts each of which in turn divides into tertiary
ducts. Quaternary ducts are beginning to arise from the ter-
tiary ducts (fig. 12). The terminal ducts present small knob-
like enlargements or end-buds. Not every gland observed at
this stage presents all of the above mentioned branches. For
example in the second inguinal gland of one specimen the pri-
mary duct has divided into two secondary ducts which remain
undivided.
206 J. A. MYERS
The time of formation of the lumen evidently is subject to
considerable variation. While its first appearance was observed
in eighteen day and nine hour and nineteen day and six hour
Roca . DIiak S:
p.d. Et. Cc. ep. in.
Fig. 3 Drawn from a section through right first thoracic developing mam-
mary gland of a female albino rat fetus of twenty days and six hours. X 300.
Zenker’s fixation; hematoxylin-eosin stain. Drawn with the aid of a camera
lucida. c., irregularly arranged developing connective tissue cells; c.t., develop-
ing connective tissue forming sheath around duct; ep. in., epithelial ingrowth or
hood; n.a., nipple anlage; p.d., primary duct ; s., sulcus surrounding nipple anlage.
STUDIES ON THE MAMMARY GLAND 207
fetuses there are still systems of ducts at twenty days and six
hours which show absolutely no trace of a lumen. In other
glands of this stage the lumina are much larger than in the pre-
ceding stages (fig. 5). When present, the lumina are better
developed in the free ends of the system of ducts, i.e., in the ter-
minal ducts and the ones from which they arise; however, quite
frequently traces of lumina are observed in the primary and sec-
ondary ducts. In no part of any system of glands observed is
there a definitive lumen present. The walls of all are irregular,
but have quite sharp boundaries. In no case are degenerating
cells found within the lumen.
Figures 4 and 5 show that the first indication of a lumen is the
appearance of a few independent lacunae. In cross section of the
ducts such lacunae are usually seen located near the center of the
developing ducts; however, they are not uncommonly found near
the periphery, at the central ends of the peripheral layer of cells.
When traced longitudinally any individual lacuna is found to
extend only a very short distance; but in serial sections other
lacunae are found forming more or less definite rows extending
along the ducts. In some glands the lacunae are present from
the end-buds well into the primary ducts.
The lacunae later increase in size and apparently flow together,
thus forming the lumina found in some individuals of this stage
. (fig. 5,1). The lumina at this stage are never continuous through-
_ out the system of ducts. But a lumen may extend throughout a
terminal duct, then with an interruption appear again in the
tertiary or secondary ducts.
Owing to individual variation, it is possible to find all of the
above described developmental stages of lumina in twenty day
and six hour fetuses.
Several of the glands of this stage were stained with Dominici’s
combination stain. In blood vessels, the corium within the epi-
thelial hood, the connective tissue immediately surrounding the
ducts, and the ordinary connective tissue in the entire gland
region were found various kinds of white blood cells including
eosinophiles. In one gland a few lymphocytes were observed
in the developing lumina of the ducts. None of the glands ex-
208 J. A. MYERS
STUDIES ON THE MAMMARY GLAND 209
amined showed such an infiltration of leucocytes as Keiffer (’02)
and others have described in the human newborn.
The processes of the connective tissue cells have elongated and
when treated with Mallory’s connective tissue stain many of
them now appear as true white fibrous connective tissue fibers.
Weigert’s elastic tissue stain revealed no trace of elastic fibers
at this stage. The developing connective tissue has so differ-
entiated that the anlages of two adult parts may now be recog-
nized. That part immediately adjacent to the ducts forms a thin
sheath around them. This sheath is the anlage of the mantle
layer. While the connective tissue between the ducts represents
the anlage of the true stroma (fig. 6, m.l., s.t.).
Lobules have not yet formed in the mammary gland.
The masses of fat which are so conspicuous in the postnatal
stages are not developed at this stage.
The foregoing stage at twenty days and nine hours brings the
description up to the condition at birth which was the starting
point in my previous paper (Myers, ’16). In newborn rats the
lumina were found to extend through the primary ducts (except
the intraepidermal portion) into the secondary ducts and to ter-
minate in the end-buds. In the primary ducts the lumina are
small irregular slit-like spaces which become continuous with the
more regular rounded lumina of the remaining ducts. One can
Fig. 4 Drawn from a section through the primary duct (near free end) of the
left second thoracic gland of a female albino rat fetus of eighteen days and nine
_ hours to show development of lumen. 550. Zenker’s fixation; hematoxylin-
‘eosin stain. Drawn with the aid of a camera lucida. c.m., condensed mesen-
chyma; l.c., small cavities (lacunae) which later fuse to form lumen.
Fig. 5 Drawing of a tangential section through a secondary duct of the
right first inguinal gland of a female albino rat fetus of twenty days and six
hours to show developing lumen. > 550. Zenker’s fixation; hematoxylin-
eosin stain. Drawn with the aid of camera lucida. c., irregularly arranged de-
veloping connective tissue cells; c.t., developing connective tissue forming shéath
around duct; J., lumen formed by fusion of small cavities (lacunae); J.c., small
cavities (lacunae).
Fig. 6 Drawn from a section through four tertiary ducts of the left first
thoracic gland of a female albino rat fetus of twenty days and six hours. 175.
Zenker’s fixation; hematoxylin-eosin stain. Drawn with the aid of a camera
lucida. t.d., tertiary ducts; m.l., developing connective tissue to form mantle
layers; st., developing connective tissue forming true stroma; l.c., lumen.
210 J. ay MYERS
safely assume that the process already begun in the eighteen to
twenty day fetuses continues until the time of birth, thus pro-
ducing the continuous lumina found in newborn rats.
The lumina at birth have not assumed their definitive form,
however. In a later study the details of the further develop-
ment of the lumina in the postnatal stages of the albino rat
will be described.
DISCUSSION AND CONCLUSIONS
In the following discussion, the nipple, the milk-ducts, the
epithelial hood, gland stroma, variation, and cephalocaudal
‘sequence in development will be successively considered.
The nipple
A comparison of figures | and 7 is sufficient to show that in the
albino rat fetus slight eminences occur in the region of the future
nipples. These eminences evidently correspond to the mam-
mary hillocks described in other forms. The mammary hillocks
in the rat fetus (as in other forms) are temporary eminences,
each being soon replaced, as has been shown, by a shallow
depression, the mammary pit. At the bottom of this pit later
occurs a slight elevation representing the nipple anlage. The
true nipple reaches only a very rudimentary stage of develop-
ment in rat fetuses. The latest stage studied (twenty days
and six hours) shows the nipple anlage as a rather slight emi-
nence at the bottom of the mammary pit (figs. 3 and 9).
The phenomena of development in the nipple and the asso-
ciated hillock and pit are rendered more intelligible by a com-
parison with the conditions found in lower forms.
The mammary hillocks first appear in rat embryos of fourteen
days (Henneberg, ’00). The present work shows that they
persist through the sixteenth day at which time they are less
conspicuous than at the fifteenth day. These hillocks apparently
occupy the positions of the future nipples. Because of their
positions and resemblance to a nipple, Schultze (92 and ’93)
in the pig and other species called them primitive nipples
STUDIES ON THE MAMMARY GLAND 211
(‘primitive Zitzen’), a misleading term since, as he observed,
they are merely transient structures.
Similar hilloeks have been observed in human embryos by
Langer (751), Rein (’82), Brouha (05), Lustig (16), and others.
They have been described by Rein (’82), Schultze (92 and ’93),
Bonnet (92) and Brouha (’05) in the following species: pig,
sheep, dog, fox, cat, rabbit, squirrel, rat, mouse, and mole.
The name mammary hillocks (‘Milchhiigeln’) was applied to them
by Bonnet (792).
The depression or fossa (mammary pit) which forms over each
developing gland resembles the pocket which contains the
nipple in some marsupials and which Owen (’68), Gegenbauer
(73) and others believed to exist in Monotremes. Bresslau in
1908 proved the non-existence of such a pouch in echidna and
ornithorhynchus. In an earlier work, however, Bresslau (’02)
observed that a definite pocket (‘Zitzentasche’) developed in
some marsupials in the region of the future nipple. Bresslau’s
findings in marsupials confirmed the work of Klaatsch (’84)
and others who showed that in marsupials a fairly deep pocket
is developed in the region of each mammary gland; and at the
bottom of each pocket a small papilla-like eminence occurs
which is believed to be the first appearance of a nipple in mam-
mals. During the resting phases of the glands the nipples
remain in the pocket, but they actually protrude from the pocket
and may be drawn out to a considerable extent while the glands
are active.
The ontogeny of the mammary gland nipple of the albino
rat apparently repeats in most respects the above described
conditions in the lower forms of mammals. In the rat we have
seen the surface over the future nipple region excavated (chiefly
by the processes of cornification and desquamation) so as to
form a definite pocket (figs. 8 and 9), the mammary pit. At
the bottom of this pit is seen in sections the proximal end of
the primary duct. Later a papilla-like elevation (the nipple
anlage) appears at the bottom of the pit. At this time the
nipple is so small that it occupies only a part of the pocket.
At birth the nipple has enlarged so as to fill the pit, with the
212 J. A. MYERS
exception of a shallow suleus which still surrounds the nipple.
The nipple in the newborn rat thus produces a slight eminence
on the surface of the skin. In an earlier paper (Myers, 716)
my low power drawings do not show the sulcus around the nipple
in rats at birth and one week of age. This is due to the fact
that over the sulcus the epidermis is slightly thickened, and also
because the sulcus contains some cornified cells. Nevertheless
under high power the sulcus is still very evident in these postna-
tal stages.
The mammary pit which develops before the appearance of
the nipple is apparently homologous with the nipple pocket
which Gegenbauer (73 and.’76), Rein (’82), Klaatsch (’84),
Bresslau (’02), and many others observed especially in mar-
supials. Bresslau (’02) believed that the mammary pit is
homologous with the marsupial pouch. Later, however (Bress-
lau 710), he regarded it as a homologue of the nipple pocket
of marsupials.
The milk ducts
In the rat fetuses the anlage of the milk duct was first ob-
served about the seventeenth or eighteenth day. At this time
the deep part of each epithelial mammary gland anlage apparently
elongates or sends out a single bud-like process which is the
primary duct anlage. This stage may be said to correspond to
Rein’s (’82) period of bud formation (‘Knospenbildung’) in
rabbits. It differs, however, from the findings of Langer (51),
Huss (’71), Kolliker (79), Rein (’82), Profé (’98), Hamburger
(00), Brouhia (05), Lustig (16), and many others in that they
observed a variable number of buds (primary duct anlages) in
man and other animal species including the horse, pig, cat and
rabbit. On the other hand it agrees with the observations of
De Sinety (77), Gegenbauer (’76), Klaatsch (84), and Brouha
(05) who reported the existence of a single primary duct in
rodents and insectivorous mammals.
Between the eighteenth and nineteenth days each primary
duct in the rat fetus presents two secondary ducts. The second-
ary ducts later present tertiary ducts. Quaternary ducts are
STUDIES ON THE MAMMARY GLAND 213
present at twenty days. Very rapid growth takes place be-
tween the twenty day stage and the newborn, as my reconstruc-
tions and cleared preparations (Myers 716) show that the ducts
are much elongated and several new divisions have occurred in
the latter.
The first few divisions of the milk-ducts in the twenty day
fetus (fig. 12) follow the true dichotomous method of branching.
The divisions farther away from the primary ducts, however,
do not come off so regularly, yet they present a very irregular
form of dichotomy. ‘The same condition obtains in the newborn
and later postnatal stages (Myers 716). Langer (51), Kolliker
(79), and Lustig (16) found that for the most part the milk-
ducts of human fetuses branch dichtomously. Ko6lliker (’79)
states that the human mammary ducts branch two to eight
times by the true dichotomous method after which the branch-
ing is somewhat irregular. The method of branching of the
milk-ducts of the albino rat, therefore, appears to be similar
to that of the human.
The terminal end of each milk-duct in all stages of the rat
fetus studied presents an enlargement. Langer (’51) noticed
such enlargements at the terminal ends of developing milk-
ducts in the human, and they have since been reported by num-
erous investigators. Formerly such terminal swellings were
believed to be true acini. The present work, however, as well
as my previous study (Myers, *16), confirms the view that they
are not true acini, but are merely growing end-buds.
The first indication of a lumen in the ducts was observed in
a rat fetus of eighteen days and nine hours. The lumina ap-
pear, however, in only a part of the ducts observed at this stage,
while at twenty days and six hours the majority of the ducts
show lumina in an early stage of development. At birth the
lumina extend from the intra-epidermal portion of the primary
ducts to within 20 or 30 micra of the free extremities of the ter-
minal ducts. Such lumina, however, have not yet reached their
definitive state.
The time of development of the lumen in the mammary ducts
is subject to considerable variation, not only in different species
214 J. A. MYERS
but in individuals of the same species. In the rabbit, Rein
(82) found the first vestige of a lumen in a very late fetus. At
five days after birth canalization is not entirely complete, but
at fifteen days the lumen extends to the tip of the nipple. It
does not open on the surface, however, owing to the presence of
cornified cells in the proximal end of the primary duct. Brouha
(05) in the rabbit four days old found two of the milk-ducts with
lumina throughout, other ducts at the same age showing only
faint traces of lumina. At twenty-five days he found the
limina completely formed for all of the ducts. In a kitten
twelve hours after birth Brouha found a part of the ducts pro-
vided with lumina. In Vespertilio murinus he found a trace
of a lumen in the milk-ducts of 20 mm. fetuses, while at birth
the lumina are quite well represented throughout the ducts.
De Sinety (75) and Lustig (16) found the Jumina begin to
appear in human milk-ducts about the sixth or seventh fetal
month, but are not completely developed until birth or later.
From the present work on rat fetuses and the foregoing ob-
servations of De Sinety (75), Rein (’82), Brouha (05), and
Lustig (16) it may be concluded that the lumina of milk-ducts
usually begin to develop during the later fetal stages, but the
definitive lumen does not appear until birth or later.
The earliest appearance of the lumen has been reported in
different parts of the milk-ducts. In the previously published
abstract of the results of the present paper (Myers, ’17) it was
stated that the lumina make their earliest appearance in the
free ends of the milk-ducts. This statement agreed with the
findings of Rein (’82), Eggeling (04), Raubitschek (04), and
Lustig (16). Further observations on a larger number of al-
bino rat fetuses, however, indicate that the lumina may appear
first in the excretory or external portions of the milk ducts, as
observed by Kolliker (50) and Brouha (’05) in the glands of
the mouse, rabbit, cat and man. We must therefore conclude
that the first appearance of the lumina of the milk-ducts is
variable and may occur in various parts of the ducts. In the
rat, however, in the majority of cases the lumina show slightly
further progress in development toward the free ends of the
ducts.
STUDIES ON THE MAMMARY GLAND 215
The manner in which the lumen is formed has likewise been
a subject of considerable controversy. It will be recalled that
in the rat fetus of about the eighteenth or nineteenth day small
irregular intercellular cavities or lacunae appear in the epithe-
lium of the milk-ducts. The lacunae are chiefly confined to
the center of the developing ducts, but may occur peripherally.
The cells and their nuclei in the region of the lacunae show no
signs of degeneration. A little later the lacunae flow together,
thus forming a lumen which is in a very incomplete stage of
development at this age. The lumina are better developed at
birth (Myers, 716), but are still incomplete. De Sinety (75),
Rein (’82), and Keiffer (02) have described the formation of
the lumina in human as a process of degeneration. ‘They state
that the central cells of the solid epithelial duct anlage degene-
rate, the débris being found in the developing lumina. My
fetal stages show no such condition, but agree rather with the
findings of Benda (’94) and Brouha (’05), who described the
formation of the lumen in the mouse, rabbit, cat and man as
a process of cell-rearrangement, rather than cell-degeneration.
The epithelial hood
The anlage of an epithelial ingrowth or hood was first observed
in one of the abdominal glands of an eighteen day and nine hour
rat fetus. Such anlages are present in most of the glands in
ninteen day fetuses. These anlages were seen to bud off
from the deeper epithelial surface funnel-shaped mammary pit.
About the twentieth day the ingrowth forms a real hood around
the proximal end of each primary duct. When examined
microscopically, the part of the hood attached to the walls of
the mammary pit is seen to be filled with a thin layer of corni-
fied cells which is continuous with the mass occupying a part of
the mammary pit. No cavity is yet present in the hood, al-
though its attachment corresponds to the region of the sulcus
between the nipple anlage and the wall of the mammary pit.
The epithelial hood has been observed by several investi-
gators (Gegenbauer, ’76, Rein, ’82, Klaatsch, ’84, in rodents and
216 J. A. MYERS
insectivorous mammals) some of whom believed it to be homol-
ogous with the marsupial pouch or the nipple pocket of marsup-
ials. As to the significance of the epithelial hood in the albino
rat I have as yet reached no definite conclusion.
Gland stroma
The majority of the investigators have observed and described
the mammary gland stroma. In the rabbit and man at the
end of the period of ‘Knospenbildung,’ Rein (82) found the
first appearance of the gland stroma. In the albino rat ac-
cording to Henneberg, the mesenchyma deep to the first anlage
of the mammary gland is condensed. The present work shows
that in the rat fetus at fifteen days the mesenchymal cells lying
nearest the mammary gland anlage are elongated and arranged
in two or three distinct rows around the anlage. At about
seventeen and eighteen days, as the primary duct buds out
from the main gland anlage it becomes well surrounded with
developing connective tissue cells, which at this stage present
long fibrous processes. As many as three or four layers of the
cells and their fibers surround each duct, while farther from the
ducts the connective tissue cells and fibers are arranged parallel
with the surface of the skin. A short time before birth, at
twenty days and six hours, the ducts are covered with a sheath
of fibrous tissue. The connective tissue external to this sheath
is somewhat condensed (fig. 6). The sheath which intimately
surrounds each duct corresponds to the part which Berka (712)
described as the mantle layer of young girls and older virgins.
The condensed tissue external to the sheath he designated as
the true stroma. In the true stroma, blood vessels and nerves
are found, but the blood vessels are not as abundant as one might
expect.
The fatty tissue enclosed by the gland stroma, which takes
an important part in the later development of the gland, was
not observed in the fetal stages.
STUDIES ON THE MAMMARY GLAND 217
Variation
Individual variations in the development of the mammary
gland are so frequent that at least mention should be made of
them. Moreover, no work on the mammary gland should be
regarded complete until the conditions have been studied in
a sufficient number of individuals to rule out all possibility of
error from individual variations.
Rein (’82) found many individual fluctuations in the develop-
ing mammary gland of human. In one pig embryo of 1.5 cm.
Schultze (’93) found only the milk line while in another embryo
of about the same size he found the ‘primitive Zitzen.’ Hen-
neberg (’00) found in one rat embryo of eleven days no indica-
tion of a mammary streak while in another embryo of the same
age a well developed streak appeared only on one side. Rau-
bitschek (04) states that probably no other organ is subject to
such great fluctuations in its development as the mammary
gland. Aki
In the present study, it has been noted that in the eighteen
day and nine hour stage of the albino rat fetus some of the
glands possessed anlages of only the primary ducts while in
others there were secondary ducts, Also the lumen began to
appear in one individual of this stage while in others there was
no trace of a lumen present. The lumen continued to develop
until at twenty days and six hours it was represented by a con-
siderable cavity in some part of most of the ducts. Yet even at
this stage an occasional individual possesses a gland without
the slightest manifestation of a lumen.
The number of mammary glands of the rat likewise is subject
to individual variation. Schickele (’99) found that in 6.66 per
cent of the rats examined, only 11 nipples were developing. In
80 per cent of his rats 12 nipples (the normal number) were pres-
ent. While in 13.33 per cent there were 13 nipples present. In
no case did he find more than 13 nipples. Henneberg (’00),
Myers (’16), also reported a variable number of glands in albino
rats. Schultze (93) in describing the mammary glands of a rat
embryo of 1.2 cm. mentioned only two thoracic pairs of glands
THE AMERICAN JOURNAL OF ANATOMY, VOL. 22, No. 2
218 J. A. MYERS
but found the usual number of abdominal and inguinal pairs.
In the case of the rat, some authors fail to report the species
studied, which should always be stated in order to avoid errors
and confusion in making.comparisons. Lantz (10) states that
the female brown rat (Mus norvegicus) has usually 12 mammae
—3 pairs of pectoral and 3 pairs of inguinal—although these
numbers are not constant, one or more teats frequently being
undeveloped. He also states that the black rat (Mus rattus)
and the roof rat (Mus alexandrinus) have only 10 mammae—2
pairs of pectoral and 3 pairs of inguinal—with but little tendency
to vary. <A variable number of mammary glands has also been
reported in many other forms, including man. Therefore, in all
morphological and histological work as well as experimental
work on the mammary gland, individual variation must be con-
sidered before drawing any definite conclusions.
Cephalo-caudal sequence in development
Henneberg’s (’00) work shows that in the early stages of de-
velopment of the mammary gland the more cephalic or thoracic
glands are better developed than the caudal or abdominal and
inguinal glands. In fact the inguinal gland anlages remain con-
siderably behind the thorad¢ic anlages. In carnivora Schultze
(93) found the more cephalic mammary gland anlages earlier
and better developed than the posterior ones at the same age.
A similar condition was found in a part of the fetuses examined
during the present work. However, when the twenty day and
six hour stage is reached the difference is not so noticeable. The
order of sequence is therefore in accordance with the general
rule that those parts occupying a more cephalic position tend
toward earlier development than those parts occupying a more
caudal position.
SUMMARY
1. In fetuses at fifteen days and nine hours the mammary
glands of the albino rat are in the club-shaped stage, the epi-
thelial anlage forming an ellipsoidal body attached to the epi-
dermis by a constricted neck.
STUDIES ON THE MAMMARY GLAND 219
2. About the seventeenth or eighteenth day the deep portion
of each anlage elongates into a long solid cord of epithelium—
the anlage of the primary duct. At this time each anlage is only
about 0.05 mm. in length. The free end of each primary duct is
directed toward the position which the future system of ducts
will occupy. At eighteen or nineteen days each of the primary
ducts present. two secondary ducts. About the twentieth day
tertiary and quaternary ducts are present. The first few divi-
sions are usually dichotomous, while the more distal ones become
somewhat irregular. Growing end-buds are present on the free
ends of the terminal ducts.
3. Between the eighteenth and nineteenth days an epithelial
projection grows in from the stratum germinativum around each
gland area. Each projection extends entirely around the pri-
mary ducts thus forming the epithelial hood.
4. The mammary pit first appears on the surface as a slight
depression over each developing gland. It is apparently formed
by the processes of cornification and desquamation of the thick-
ened epithelium. The pit is well developed at nineteen or
twenty days.
5. The nipple anlage was first observed in twenty day and six
hour fetuses. At this stage it is a small papilla-like eminence
lying at the bottom of the mammary pit. The nipple reaches
only a rudimentary stage of development in the prenatal stages
of the albino rat.
6. The lumina of the ducts were first observed in eighteen day
and nine hour fetuses. They were not confined to any definite
part of the system of ducts, but usually appeared slightly better
developed toward the free ends of the ducts. The lumina do
not reach their definitive stage in the fetal state. In the fetuses
examined, the lumina are apparently formed by a rearrangement
of the cells, thus producing numerous lacunae which later flow
together to form the incomplete lumina of the Jatest stage studied.
No traces of cell degeneration were observed.
7. In the earliest stages studied the mesenchymal cells are
condensed. around the mammary gland anlage. Later these
cells elongate and develop long fibrous processes. At twenty
220 J. A. MYERS
days and six hours these cells and fibers constitute the greater
part of the gland stroma which may be divided into two parts:
(1) the mantle layer which is a thin layer immediately sur-
rounding the ducts; (2) the true stroma which les between the
ducts and outside of the mantle Jayer. The true stroma con-
tains the Jarger blood vessels and nerves of the glands.
LITERATURE CITED
Benpa, L. 1894 Das Verhiltnis der Milchdriisen zu den Hautdriisen. Derma-
tolog. Zeitschr., Bd. 1.
Berka, F. 1911 Die Brustdriise verschiedener Altersstufen und wahrend der
Schwangerschaft. Frankfurter Zeitschrift fiir Pathologie, vol. 8.
Bonnet, R. 1892 Die Mammarorgane im Lichte der Ontogenie u. Phylogenie.
Ergebn. d. Anat. u. Entw., Bd. 2. \
1897 Die Mammarorgane im Lichte der Ontogenie u. Phylogenie.
Ergebn. d. Anat. u. Entw., Bd. 7.
Bressuau, E. 1902a Beitrige zur Entwicklungsgeschichte der Mammaror-
gane bei den Beutelthieren. Zeitschrift f. Morphologie u. Anthrop-
ologie, Bd. 4.
1902 b Weitere Untersuchungen iiber Ontogenie und Phylogenie des
Mammarapparates der Séugetiere. Anat. Anz., Bd. 21.
1908 Die Entwickelung des Mammarapparates der Monotremen,
Marsupialier und einiger Placentalier. I. Entwicklung und Ur-
sprung des Mammarapparates von Echidna. Semon’s Zoolog.
\ Forschungsreisen, Bd. 4, Lieferung 5.
1910 Der Mammarapparat (Entwicklung und Stammesgeschichte).
Ergebn. d. Anat. u. Entw., Bd. 19.
1912 Ueber Hyperthelie. Miinchener Med. Wochenschr., Jahrg. 59,
S. 2793-2795.
Brovuwa, Dr. 1905 Recherches sur les diverses phases du developpement et de
l’activite de la mamelle. Archives de Biologie, T. 21.
Danrortu, C.H. 1916 The use of early developmental stages in the mouse for
class work in embryology. Anat. Rec., vol. 10.
Dr Stnety 1875 Recherches sur la mamelle des enfants nouveau-nes. Arch.
de physiol. norm. et patholog., T. 2.
1877 Sur le developpement et l’histologie comparée de la mamelle.
Comptes rendus des Séances de la société de biologie.
Eaartine, H. 1904 Ueber ein wichtiges Stadium in der Entwicklung der
foetale Mamma beim Menschen. Anat. Anz., Bd. 24.
1905 a Ueber die Driisen des Warzenhofs beim Menschen. Jenaische
Zeitschr. Naturwiss., Bd. 39.
1905 b Ueber die Stellung der Milchdriise zu den iibrigen Haut-
driisen. Semon’s Zool. Forschungsreisen, Bd. 4, Lieferung 5.
GEGENBAUER, C. 1873 Bemerkungen iiber die Milchdriisen-papillen der
Ssugethiere. Jenaische Zeitschr. f. Med. u. Naturw., Bd. 7.
STUDIES ON THE MAMMARY GLAND Do
'GEGENBAUER, C. 1876 Zur genaueren Kenntniss der Zitzen der Siiugethiere.
Morpholog. Jahrb., Bd. 1.
1884 Zur niheren Kenntniss des Mammarorgans von Echidna.
Morpholog. Jahrb., Bd. 9.
Haackr, W. 1885 On the marsupial ovum, the mammary pouch and the male
milk glands of Echidna hystrix. Proce. of the Royal Society, London.
HamBurGER, Ciara 1900 Studien zur Entwickelung der Mammarorgane. I.
. Die Zitze von Pferd und Esel. Anat. Anz., Bd. 18.
HENNEBERG, BRuNNO 1900 Die erste Entwickelung der Mammarorgane bei
der Ratte. Anat. Hefte, Bd. 13.
Huss, M. 1871 Beitrige zur Entwicklungsgeschichte der Milchdriise. Je-
naische Zeitschr. fir Naturw., Bd. 7.
Jackson, C. M. 1912 On the recognition of sex through external characters in
the young rat. Biological Bulletin, vol. 23.
Kerrrer, H. 1902 La glande mammaire chez le foetus et chez le nourrisson.
Bull. Soc. Belge de Gyn. et d’Obstet., T. 13.
Kuaatscu, H. 1884 Zur Morphologie der Siugethierzitzen. Morphol. Jahrb.,
Bd. 9.
1895 Studien zur Geschichte der Mammarorgane. I. Theil: Die
Taschen und Beutelbildungen am _ Driisenfeld der Monotremen.
Semon’s Zool. Forschungsreisen, Bd. 2.
KO6uirkEeR, TH. 1850 Mikroskopische Anatomie. Bd. 2.
1879 Beitrige zur Kenntniss der Brustdriise. Verh. d. phys.-med.
Ges. zu Wiirzburg, N. F., Bd. 14.
LANGER, Cart 1851 Ueber Bau und Entwicklung der Milchdriise. Denk-
schrift der Wiener Akad. d. Wiss., Bd. 3.
Lantz, Davip E. 1910 The natural history of the rat. In “The rat and its
relation to the public health,” by various authors. P. H. and M. H.
Service, Washington, D. C.
Lustic, Hirnpa 1916 Zur Entwicklungsgeschichte der menschlichen Brust-
driise. Archiv f. mikr. Anat., Bd. 87.
Morean, J. 1833 Description of the mammary organs of the kangaroo. Trans-
act. of the Linnean Society of London, vol. 16.
Myers, J. A. 1916 Studies on the mammary gland. I. The growth and dis-
tribution of the milk-ducts and the development of the nipple in the
albino rat from birth to ten weeks of age. Am. Jour. Anat., vol. 19.
(Abstract also published in the Anat. Rec., 1916, vol. 10, p. 230.)
1917 The fetal development of the mammary gland in the female
albino rat. (Abstract.) Anat. Rec., vol. 11, p. 390.
Owen, R. 1832 On the mammary glands of the Ornithorhynchus paradoxus.
Philos. Transactions, vol. 122.
1865 On the marsupial pouches, mammary glands and mammary
foetus of Echidna hystrix. Philos. Transactions, vol. 155.
1868 Comparative Anatomy and Physiology of Vertebrates, vol. 3.
Prork, O. 1898 Beitrige zur Ontogenie und Phylogenie der Mammarorgane.
Anat. Hefte, Bd. 11.
RaupitscHek, H. 1904 Ueber die Brustdriisen menschlicher Neugeborencn.
Zeitsch. f. Heilkund. Abth. f. pathol. Anatomie, Heft 1.
222 J. A. MYERS
Rein, G. 1882 Untersuchungen iiber die embryonale Entwicklungsgeschichte
der Milchdriise. Archiv fiir mikr. Anatomie, Bd. 20 and 21.
Ruce, G. 1895 Die Hautmusculatur der Monotremen und ihre Beziehungen
zu dem Marsupial- und Mammarapparate. Semon’s Zool. For-
schungsreisen, Bd. 2 (Jenaische Denkschriften, Bd. 5).
ScHICKELE, G. 1899 Beitriige zur Morphologie und Entwickelung der normalen
und iiberziihligen Milchdriisen. Zeitschrift f. Morphologie und
Anthropologie, Bd. 1, Heft 3.
Scuin, L. 1912 Recherches sur la glande mammaire, sur les phases qu’elle
présente au cours de son évolution et leur determinisme. Thése,
Lyon.
Scnuttze, O. 1892 Ueber die erste Anlage des Milchdriisenapparates. Anat.
Anz., Bd. 8.
1893 Beitrag zur Entwicklungsgeschichte der Milchdriisen. Ver-
handl. d. phys. med. Gesell. in Wurzburg, Bd. 26.
Sosporra, J. 1895 Die Befruchtung und Furchung des Eies der Maus. Archiv
f. mikr. Anat., Bd. 45.
Soporra, J., AND BurckHARD, G. 1911 MReifung und Befruchtung des Eies der
weissen Ratte. Anat. Hefte, Bd. 42.
PLATE 1
EXPLANATION OF FIGURES
7 External view of a wax model reconstructed from the right first thoracic
gland of an albino rat fetus of fifteen days and nine hours. X 100. e.s., emi-
nence (mammary hillock) on surface of skin produced by developing mammary
gland. ;
8 External and part of internal view of a wax model reconstructed from the
left first inguinal gland of a female albino rat fetus of eighteen days and nine
hours. X 50. n.p., depression representing mammary pit; p.d., primary duct
anlage.
9 External view of a wax model reconstructed from the left second inguinal
gland and surrounding region of a female albino rat fetus of twenty days and
six hours. »X 50. n.a., nipple anlage; n.p., mammary pit; s., sulcus surround-
ing nipple anlage.
10 Internal view of a wax model reconstructed from the right first thoracic
gland of an albino rat fetus of fifteen days and nine hours. X 100. m.a., ellip-
soidal mass of cells (mammary gland anlage) connected to epidermis through a
constricted neck (nk).
11 Internal view of a wax model reconstructed from the right abdominal
gland of a female albinorat fetus of eighteen daysand nine hours. X 50. e.6.,
end-bud; p.d., primary duct; s.d., secondary ducts.
12 Internal view of a wax model reconstructed from the left first inguinal
gland of a female albino rat fetus of twenty days and six hours. X 50. e.b.,
end-bud; ep.in., epithelial ingrowth (hood); p.d., primary duct; s.d., secondary
duct; t.d., tertiary duct.
i
STUDIES ON THE MAMMARY GLAND PLATE 1
J. A. MYERS
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AUTHORS’ ABSTRACT OF THIS PAPER ISSUED
BY THE BIBLIOGRAPHIC SEPRVICH AUGUST IS.
THE EXISTENCE OF A TYPICAL OESTROUS CYCLE
IN THE GUINEA-PIG—WITH A STUDY OF ITS HIs-
TOLOGICAL AND PHYSIOLOGICAL CHANGES
CHARLES R. STOCKARD AND GEORGE N. PAPANICOLAOU
Deparliment of Anatomy, Cornell University Medical School, New York City
ONE TEXT FIGURE AND NINE PLATES
1. INTRODUCTION
The existence of a more or less regular and definite oestrous
eycle has been recognized in a number of mammals, particularly
among the different classes of primates, carnivores, ungulates
and insectivores. Yet very little is actually known or under-
stood regarding the oestrous cycles and heat periods of a great
many other very common mammals. Strangely enough, our
knowledge of the sexual rhythm in the guinea-pig is much con-
fused and not properly understood despite the great number of
breeding experiments and the several studies of the sexual con-
ditions which have been performed on this animal.
While conducting an extensive breeding experiment with
guinea-pigs for the past several years it has become more and
more desirable to know their exact oestrous periods.! A care-
ful study of the existing literature bearing on this subject serves
merely to produce uncertainty and confusion regarding their
1 Throughout this paper we have used the terminology proposed by Heape,
Quar. Jour. Mic. Se., vol. 44, 1900, and adopted by Marshall and others. An-
oestrous period or anoestrum, period of rest in the female; prooestrum, the
first part of the sexual season; oestrus or oestrum, especial period of desire in
the female; metoestrum, the short period when the activity of the generative
system subsides and the normal condition is resumed in case conception did not
occur; dioestrum, the short period of rest which in some mammals lasts only
afew days. Such a short cycle as we shall describe in the guinea-pig consisting
of four periods the prooestrum, oestrum, metoestrum and dioestrum is known as
a dioestrous cycle.
226 CHARLES R. STOCKARD AND G. N. PAPANICOLAOU
ovulation times and heat seasons. The reason for such a lack
of knowledge is that these small rodents do not reveal in a very
evident manner the existence of their typical sexual rhythm as
do many mammals of other classes.
The guinea-pig never, or only in rare cases, shows an external
flow from the vagina, and there is no easily noticeable change in
the appearance of the external genital organs during the differ-
ent periods of sexual activity. The only expression generally
observed of the sexual condition or heat period in the female
is her willingness to accept the male, and this sign is, of course,
only manifested when a male is present and a copulation takes
place. The copulation then brings about the disturbing factor
of pregnancy and the observation of the return of the heat
period is prevented. The practical difficulties in observing
successful copulation in these animals makes the study of their
sexual conditions still more difficult.
Marshall (10), in a recent summary has stated the case as
follows:
It is difficult to determine the length of the prooestrum and oestrus
in rodents, since the external changes which characterize these condi-
tions are comparatively slight. Heape says that the prooestrum in
the rabbit lasts, probably, from one to four days. At this time the
vulva tends to become swollen and purple in color, but there is no
external bleeding. The same may be said of the rat and the guinea-
pig; but, in the experience of the writer, zt 2s generally impossible. to
detect the prooestrous condition in either of these animals with absolute
certainty.
It must be recalled here that Marshall has devoted a great
deal of study to this subject.
The difficulty in observing signs of heat in the guinea-pig has
led a numbers of workers during the past fifty years to a study of
the ovaries in order to establish the ovulation cycle. The re-
sults of such studies, as we shall point out beyond, are inaccurate
and confusing in all cases.
Recognizing the above state of affairs, we determined to as-
certain whether by a more minute examination of the genital
organs of the female it might not be possible to observe an oestrous
cycle. In order to examine the vagina thoroughly we have in-
DIOESTROUS:- CYCLE IN THE GUINEA-PIG Di
troduced a small nasal speculum which facilitates a clear view
of the interior and a smear is made of any fluid that may be
present.
A microscopic study of these vaginal fluids, to be described
in the following pages, has shown that the guinea-pig possesses
a perfectly regular and typical dioestrous cycle. And further,
the surprising fact that the composition of the fluids is exactly
comparable to the menstrual fluid taken from so high a mammal
as the monkey. Heape, (99), states that the menstrual fluid of
the monkey contains a mucous secretion of the uterine glands,
blood corpuscles, particles of stroma and epithelium from the
uterus and the vagina and leucocytes. All of these elements are
present in the fluid from the vagina of the guinea-pig during
heat though the relative amounts differ from those in the
monkey and the fluid is rarely sufficiently abundant to be recog-
nized on the vulva.
The great advantage of this simple method of examination
for the study of the oestrous cycle in these mammals which show
no external signs of heat is evident, and we trust that the method
may prove useful to those who find it necessary or desirable to
know accurately the sexual periods in animals used fo: experi-
mental breeding.
Having begun a study of the vaginal smears from guinea-pigs
we have been led to a more complete consideration of the uterine
changes which alter the composition of these smears, and finally
to an investigation of the changes in the ovary and the process
of ovulation and corpus luteum formation which accompany the
activities on the part of the uterus. The present contribution
comprises the results of these investigations.
2. CONSIDERATION OF THE LITERATURE ON OVULATION IN THE
GUINEA-PIG
It has been recognized for more than half a century that the
guinea-pig comes into heat very quickly after giving birth to a
litter of young. This period immediately following parturition
has been the starting point for the great majority of studies on
the sexual behavior of this animal and it has been demonstrated
228 CHARLES R. STOCKARD AND G. N. PAPANICOLAOU
frequently by such studies that ovulation takes place a few
hours after parturition, the female accepting the male at that
time. These facts are generaily admitted but the most varied
opinions prevail regarding the times of the subsequent ovulations,
when conception does not occur soon after parturition.
The question whether ovulation in the guinea-pig is spontane-
ous or dependent upon copulation has often been raised by vari-
ous workers. The majority are of the opinion that ovulation is,
or may be, spontaneous although influenced by copulation, and
that there is no definite regularity or typical periodicity in the
ovulation cycles.
Bischoff, was one of the oldest advocates of the theory of spon-
taneous ovulation. In a special paper devoted to the study of
this problem in 1844, and later in a study of the development of
the guinea-pig (’52), he defended the view that the guinea-pig,
like all other mammals, has a spontaneous ovulation. Bischoff
states that the mature eggs reach the oviducts through the rup-
ture of the greatly distended Graafian follicles during the first
twenty-four hours following parturition. This fact, he points out,
had previously been observed and was generally accepted by the
earlier investigators with the exception of Schulz, 1829, who
failed to recognize a heat period before the fifteenth day after
parturition, and sometimes even to the forty-ninth day.
According to Bischoff copulation takes place within three hours
after parturition. He agrees with the earlier statements of
Aldrorandi, Legullois, Fraser and Schultz regarding the length
of gestation, or period of pregnancy, as being about nine weeks,
which is very nearly correct, sixty-two days being the normal
length of time. He held that the return of the heat period did
not follow any regular periodicity: ‘‘Wenn die Befruchtung
unmittelbar nach der Geburt verhindert wird, so scheint die
Wiederkehr der Brunst an keine ganz bestimmte zeit gekniipft
zu sein, sondern von Umstiinden der Individualitit, des Alters,
der Jahreszeit, der Fiitterung, ete., abzuhingen.” In four
cases in which the females were prevented from copulating for
some time after they gave birth to young a copulation occurred
40, 50, 51 and 51 days after the birth.
DIOESTROUS CYCLE IN THE GUINEA-PIG 229
Reichert (’61), confirmed the observations of Bischoff regarding
the existence of a heat condition and an ovulation process shortly
after parturition—Reichert found many fertilized eggs in the
oviducts 18, 19, 20 and 22 hours after parturition which showed
by their condition that copulation must have taken place many
hours before. His opinion is that the Graafian follicles rupture
about twelve to fourteen hours after copulation.
Many recent authors have incorrectly stated Reichert’s posi-
tion and assert that he claimed ovulation in the guinea-pig not
to be spontaneous but to depend upon copulation. This is due
to a misinterpretation of Riechert’s ideas, originated by Bischoff
in his second paper, 1870, which is chiefly an answer to Reichert’s
arguments. No doubt many of the incorrect notions regarding
Reichert’s position have resulted from authors reading this
paper by Bischoff without referring to Reichert’s own paper for
his exact position.
Reichert explains his position very clearly as follows:
Es wire wiinschenswerth die Zeit genau angeben zu kénnen, in
welcher das Ei nach der Begattung aus dem Graaf’schen Follikel
ausgestossen wird um die Einwirkung der Begattung auf das Austreten
der Eichen bemessen zu kénnen. Es ist zwar zu keiner Zeit auch nur
wahrscheinlich gewesen, dass das bis zu den EHierstécken vordringende
Sperma irgend wie direkt die Lésung der Eichen oder richtiger das
Bersten der Graaf’schen Follikel bewirken kénne. Es ist ferner die
bei anderen Thieren bekannte Tatsache, dass reife, selbst eingekapselte
Kier auch ohne vorausgegangene Begattung gelést werden durch
Bischoff’s Versuche auch fiir die Scdugethiere ausser Zwerfel gesetat.
Das Bersten aber der Graaf’schen Follikel erfolgt unter vermehrtem
Zudrang des Blutes zu denselben und in Folge der starken Vergrés-
serung ihres Inhaltes, des gallertartigen Fluidums und auch der Zellen
der Membrana granulosa, sowie des Discus proligerus; das Eichen
selbst vergréssert sich in der Brunstzeit wenig oder vielleicht gar
nicht; dasselbe léset sich nicht, es wird, so zu sagen, von der Mutter
ausgestossen. Daraus geht ferner hervor, dass die Begattung mit
ihren aufregenden Wirkungen auf das Mutterthier, insbesondere auf
den Zudrang des Blutes nach den geschlechtstheilen, einen sehr wesent-
lichen Antheil am Bersten des Graff’schen Follikels und so also an der
Befreiung des Eichens haben kann und haben muss.
This quotation shows that Reichert did not deny the existence
of a spontaneous ovulation, but claimed that copulation had an
important influence on the process of breaking the Graafian
230 CHARLES R. STOCKARD AND G. N. PAPANICOLAOU
follicle. He also admits that the existence of a spontaneous
ovulation is proven for mammals by the experiments of
Bischoff. The difference between the opinions of Reichert and
Bischoff is not that the one denies and the other admits the exist-
ence of a spontaneous ovulation, but that the one believes copu-
lation to exert an important influence over ovulation, while the
other holds that such an influence, if it exists at all, is not really
great. Leo Loeb (11), who has studied the problem of ovulation
in the guinea-pig very recently, still claims that copulation exerts
an influence over the time of ovulation. That Bischoff also
finally thought that there might be an influence on ovulation
as a result of copulation is shown by the followmg remark from
his second paper:
Sie meinen nur, es giibe doch auch noch Erscheinungen, welche
zeigen dass die Minnchen und die Begattung auch einen Einfluss
darauf ausiiben. Wenn dieser Einwurf so gehalten wird, dass er
(name'y Reichert) zugesteht, die Erschemmung an und fiir sich ist
vollkommen unabhingig von dem Mannchen, dieses aber kann doch
forderlich darauf einwirken, so wird dadurch nicht mehr gesagt, als
wenn man sagen wiirde, eine gute Erndhrung, giinstige. Verhaltnisse
der Temperatur und des Klimas haben ebenfalls einen Einfluss auf die
Reifung und Loslésung der Eier, und diese vielleicht einen noch
erésseren als die Gegenwart des Ménnchens und die Paarung. Und
wirklich stecht auch gar Nichts entgegen, dem Mannchen in diesem Sinne
einen Hinfluss eonzurdumen.
Hensen (’76), also recorded that in the guinea-pig a copulation
takes place shortly (about one hour) after parturition and six to
ten hours later an ovulation follows. In cases where this first
ovulation was not followed by pregnancy he recorded another
ovulation 17, 18, 35 and 37 days later in the different cases. The
duration of pregnancy he found to be 66 days—This along with
Bischoff’s record of an ovulation 48 and 44 days after parturi-
tion made it difficult to admit that the guinea-pig had regular
periodical ovulations every eighteenth day. Hensen, therefore,
believed that the guinea-pig probably did not have a sharply
expressed periodicity—‘‘Es scheint also die Brunstzeit der
Meerschweinchen nicht scharf periodisch zu sein.”
Rein (’83), again reports the existence of a condition of heat
in the guinea-pig within twenty-four hours after parturition.
DIOESTROUS CYCLE IN THE GUINEA-PIG 231
Regarding the occurrence of further heat periods Rein failed
to observe any regular periodicity. ‘Im Eintreten der Brunst
habe Ich keine Periodicitiét bei den Versuchstieren bemerkt.”’
The foregoing studies are chiefly of historic interest yet they
show that these earlier workers recognized the occurrence of
ovulation shortly after parturition and were uncertain or con-
fused regarding the time or periodicity of subsequent ovula-
tions. Little of definite value has ever appeared in the litera-
ture to further clear up the last point. We may now briefly
consider the more recent contributions which bear on the sub-
jects of ovulation and oestrous in the guinea-pig.
Rubaschkin (05), gives a detailed description of the sexual
conditions in the guinea-pig. He also recognized, as did the
earlier observers, that a condition of heat followed shortly after
parturition. In almost all females killed a few hours (up to
fifty hours) after the birth of a litter an ovulation had occurred.
He never observed ovulation as early as five hours after parturi-
tion though he found fertilized eggs in the oviducts as early as
fifteen and seventeen hours after. Copulation occurs directly
after having given birth to young but for later heat periods
Rubaschkin was unable to demonstrate any regular periodicity.
“Es ist mir nicht gelungen, eine bestimmte Frist fiir das
Auftreten der Brunst festzustellen.”’
He did observe, however, that in some animals ten to twelve
days after having given birth to young the entrance of the
vagina showed some signs of heat activity. ‘‘Oeffnung der
Vagina und Roéthung der Vaginaldffnung.”’ He claimed that
heat ceased to recur after the month of October, at least when
the animals were kept in a cold place. The duration of preg-
nancy was reported by Rubaschkin in three cases to be ten
weeks.
Rubaschkin thus failed to recognize the regular oestrous
cycles in these animals and also states the gestation period some-
what too long.
K6nigstein in 1907 recorded the results of observations made
on eighteen rats, one guinea-pig and five rabbits. He states
that in the rodents heat occurs immediately after giving birth
232 CHARLES R. STOCKARD AND G. N. PAPANICOLAOU
to the young and lasts for twenty-four hours. Copulation only
takes place during heat and if pregnancy fails to occur at the
period just after parturition the next heat periods follow after
intervals of three to four weeks.
Konigstein also examined sections of the genital tract giving
some important histological descriptions based chiefly on the
rat—we shall return to a consideration of these observations in
connection with our findings on the guinea-pig.
Bouin and Ancel (710), are of the opinion that guinea-pigs do
not have a spontaneous ovulation, the process being dependent
upon copulation. However, these workers seem to have reached
this opinion from observations made on rabbits which were the
chief objects of their study. Despite the striking classification
which they make of animals having a spontaneous ovulation
(monkeys, dogs, horses, cows) and those not having spon-
taneous ovulation (rabbits, guinea-pigs, cats) they admit that
rare exceptions are possible and that in any animal an ovulation.
might occur independently of a copulation.
C’est 14 un fait général, mais soumis 4 des exceptions rares. II
peut arriver que des animaux 4 ovulation non spontanée opérent la
déchirure de leurs follicules mirs en l’absence de tout rapprochement
sexuel. Nous-méme et M. Villemin avons constaté le fait chez le
Lapin. M. Mulon vient également de l’observer chez le cobaye.
During the past several years Leo Loeb (11 a, b) has contrib-
uted extensive and valuable studies bearing upon the sexual
cycles in guinea-pigs, considering in particular the function and
importance of the corpus luteum. Loeb examined a great num-
ber of ovaries at different periods, beginning with the time of the
first copulation after parturition and concludes, as Rubaschkin
1905 and others had previously done, that the cyclic changes in
the ovary take place independently of copulation. Loeb thought
that the ovulations followed no exact and regular periodicity
in all cases. The periodicity differed among the individuals and
was influenced by certain external factors, particularly copulation.
To quote:
The exact time at which the new ovulation occurs varies however
somewhat in different animals, ovulation occurring earlier in some ani-
DIOESTROUS CYCLE IN THE GUINEA-PIG 233
mals than in others. In some cases it can be hastened through certain
external factors, especially copulation, but in the large majority of
cases it occurs sooner or later even without a preceding copulation.
He holds that eight days after ovulation large follicles are pres-
ent in the ovary but sometimes ovulation may not occur for
twenty or twenty-four days.
The ‘sexual period,’ period between two ovulations, according
to Loeb lasts usually twenty to twenty-five days instead of being
about two weeks, the time necessary for mature follicles to ap-
pear. This delay in ovulation in spite of the presence of mature
follicles within eleven to thirteen days, he believes is due to a
mechanism in the ovary which prolongs the cycle, the corpus
luteum begins this mechanism. The corpus luteum degenerates
after a period of growth lasting from seventeen to twenty days
and thus ovulation occurs about once in three weeks. We shall
show beyond by a demonstration of the oestrous cycles, that
Loeb’s deductions drawn from studies of the histology of the
ovary are incorrect and, therefore, cannot be employed for
determining the ovulation cycles in these animals.
Loeb further finds that when the corpus luteum is cut out |
immediately after an ovulation, the next ovulation occurs soon
after mature follicles are developed—about thirteen to fifteen
days. Under these conditions the normal sexual cycle is re-
established—but even here his periods are not exact being
somewhat shorter than are actually normal.
The very varied time results obtained by Loeb may be given
as follows: First, no ovulation has been found under normal
conditions before the fifteenth day after the last copulation.
Second, in a group of thirty-eight guinea-pigs killed fourteen
days and eighteen hours and nineteen days and fifteen hours
after the last copulation—one had ovulated about the sixteenth
day, another the eighteenth and another at the nineteenth day,
while the remaining thirty-five had not yet ovulated. Third,
in a lot of twenty-two guinea-pigs, twenty to twenty-six days
after the last copulation, one had supposedly ovulated at the
eighteenth day, four at the nineteenth day, one at the nine-
teenth to twentieth day, one at the twenty-third and one at the
THE AMERICAN JOURNAL OF ANATOMY, VOL. 22, NO. 2
234 CHARLES R. STOCKARD AND G. N. PAPANICOLAOU
twenty-fiith day and a half, while fourteen had not yet ovulated.
fourth, in a lot of six animals killed twenty-six to thirty-four
days after the last heat period or copulation, only one had
already ovulated.
A recapitulation of these results may be stated thus: under
fitteen days no ovulation; sixteenth day, one; eighteenth day,
two; nineteenth day, five; nineteenth to twentieth day, one;
over fourteen days and eighteen hours and nineteen days and
fifteen hours, thirty-five; twenty-third day, one; twenty-five
and a half days, one; over twenty to twenty-six days, fourteen;
twenty-sixth to thirty-fourth day, one; over twenty-six to thirty-
four days, five. These figures as Loeb points out do not show
any regularity in the occurrence of the ovulation process and, as
we shall show beyond, they demonstrate how difficult or almost
futile it is to attempt to solve the sexual cycles of an animal by a
simple study of the ovarian conditions found on killing the ani-
mals at different periods. ‘To anticipate slightly, the figures
above show that Loeb entirely failed to discover the presence of
a definitely regular periodicity in the ovulation process of the
guinea-pig. Thus his examinations though much more thor-
ough were as ineffective as those of the previous workers.
In 1913, Lams gave an instructive review of this problem. He
again confirmed the long known fact that a heat period followed
parturition in the guinea-pig. The copulation was found to take
place within two to four hours after the delivery while ovulation
occurred from twelve to seventeen hours after. Thus copula-
tion generally preceded ovulation without being its cause.
Lams gives no data on the occurrence of later ovulations but
devotes himself to a detailed account of fertilization and the
early development of the egg. !
A consideration of the sum total of these various observations
compels the admission that the opinions concerning the oestrous
cycles in the guinea-pig are highly confused and totally unsat-
isfactory for application in exact breeding experiments. The
one fact which presents itself was established by the earliest
workers and confirmed by all subsequent studies—that is, that
a period of heat follows within the first few hours after parturi-
DIOESTROUS CYCLE IN THE GUINEA-PIG Bay
tion. In the literature only Schulz (’29), according to Bischoff
(52), denies this fact.
No typical rhythm has been established so far for the subse-
quent ovulations in the guinea-pig. All observers who have
examined a number of ovulations found great differences in the
supposed periods of time intervening between two ovulations as
we have reviewed in detail above. The numbers give no evi-
dence of a regular periodicity in the ovulation process but on the
contrary would lead one to believe that the greatest irregularity
in time intervals was the rule.
On the other hand, really no observations exist to show any-
thing like the occurrence of periodic changes in the uterus and
vagina accompanying the return of the heat periods. Such a
thing as a regular oestrous or preoostrous flow is completely
undiscovered in these animals. .
Konigstein (’07), has examined sections of the uterus and
vagina of a guinea-pig, and Blair-Bell (’08), has drawn com-
parisons giving many interesting observations, but they failed
entirely, or made no attempt, to observe the regular reappear-
ance of a definite order of changes in either the uterus or vagina
of this animal.
3. OBSERVATIONS ON THE LIVING ANIMALS
During the past six years we have been using guinea-pigs in an
extensive breeding experiment and it has. become more and more
evident as our work goes on that the existing notions of the ovula-
tion periods in these animals are of no practical value, or are
practically incorrect. In a number of the experiments it be-
came important to know accurately when the females ‘came into
heat’ and when ovulation took place. We had concluded, from
numerous observations as well as theoretically, that the female
guinea-pig very probably had a definitely regular and periodic
sexual cycle if it could be worked out exactly. On account of
the need of this exact information, we have studied the oestrous
cycle in these animals during the past eighteen months.
Most other attempts at a solution of this problem have cen-
tered in a study of the ovary which necessitated either its removal
236 CHARLES R. STOCKARD AND G. N. PAPANICOLAOU
by operation or the killing of the animal. In either case the pro-
cedure brought to a conclusion the observation or experiments on
the ovulation cycles in that specimen. Recognizing, on the
other hand, that no thorough investigation of the uterus and
vagina in the living female had been made, it occurred to us
that possibly oestrous changes might take place even though
they are so feebly expressed as not to be noticeable on casual
observation. ‘The absence of an apparent oestrous or prooestrous
flow from the vagina of the guinea-pig has, as before mentioned,
no doubt been the chief reason for the general lack of knowledge
of the oestrous cycle. It was therefore determined to make a
minute examination of the contents of the vaginae of a number of
females every day for a long peroid of time, to ascertain whether
a feeble flow might exist although insufficient in quantity to be
noticed at the vaginal orifice or vulva.
The observations were made by using a small nasal speculum
which was introduced into the vagina and the arms opened apart
by means of the thumb screw. The speculum permits an ex-
amination of the entire surface of the vaginal canal. In this
way the vaginae of a number of virgin females have been exam-
ined daily and smears made from the substances that happened to
be present in the lumen.
By the use of such a simple method, it was readily deter-
mined after examining the first lot of animals for a few months
that a definite sexual period occurs lasting for about twenty-
four hours and returning with a striking regularity every fifteen
or sixteen days. During this twenty-four hour period the
vagina contains an abundant fluid which is for about the first
half of the time of a mucous consistency. The vaginal fluid then
changes into a thick and cheese-like substance which finally be-
comes slowly liquified and serous. This thin fluid exists for a
few hours and then disappears. Occasionally toward the end
of the process a slight trace of blood may be present giving the
fluid a bloody red appearance, otherwise it is milk-white or
cream-color.
According to the changes in appearance and consistency of the
vaginal fluid, one may distinguish four different stages. The
DIOESTROUS CYCLE IN THE GUINEA-PIG 237
first stage having a mucous secretion, a second stage the cheese-
like secretion, a third stage with the fluid becoming serous and a
fourth stage, not always recognized, during which a bloody dis-
charge is present. The duration of these several stages is sub-
ject in the different animals to individual variations. The first
stage, however, is generally longest and lasts from six to twelve
hours or even more and during this time there is a gradually in-
creasing quantity of the mucous secretion which at its height is
very abundant and fills the entire lumen of the vagina. The
second stage is shorter, lasting from two to four hours, and
passes gradually over into the third stage which lasts from four
to six hours. The fourth stage is the shortest, only about one
to two hours long, and for this reason it is often missed in exam-
ining the animals during the periods. It is also possible, as
mentioned above, that the fourth stage may not typically exist
in all individuals and the quantity of blood present is very dif-
ferent in the different specimens. ‘The succession in which these
stages follow one another is remarkably definite. We have
never observed any change in the typical sequence of the stages
and the time consumed by the entire process is generally as
stated about twenty-four hours.
A macroscopical examination of the uterus and vagina during
this period of sexual activity shows the entire genital tract to be
congested. The vessels to the ovary, uterus and vagina are
large and conspicuous, the uterine horns and the vagina are
slightly swollen and inflamed. However, as soon as this short
period of activity is over, the congestion disappears and the
uterus and vagina take again their normal pale aspect. At the
same time the vaginal fluid diminishes and the vagina, especially
during the first week after this sexual activity, is as clean as
possible showing none of the secretion. The external vaginal
orifice, which during the period of activity is more or less open
actually showing in a few cases a little fluid or some blood, closes
and becomes less accessible after the period.
During the second week following oestrus a little mucous dis-
charge begins to appear in the vagina and increases progressively
indicating that the new period of activity is nearer and nearer
238 CHARLES R. STOCKARD AND G. N. PAPANICOLAOU
approaching. The orifice of the vagina is sometimes open dur-
ing this stage and thus explains why this sign, which was observed
before, does not make it possible to detect the actual time of
the regular oestrous activity. Rubaschkin has observed the
opening of the vagina ten to twelve days after parturition, but
this period of time is certainly too short to indicate the return
of heat. We agree with Rubaschkin in stating that during the
ovulation the vagina is open, but we do not admit that the oppo-
site is also true, that the opening of the vagina indicates unmis-
takably the return of the ovulation process.
4. MICROSCOPIC STRUCTURE AND CHANGES OF THE VAGINAL
FLUID
A microscopical examination of the smears prepared from the
vaginal fluid taken at the several stages separated above shows
decidedly typical differences. The cellular character of a smear
made at a given stage differs from the cellular make-up of all
other stages. The relative numbers of various cell types in the
fluid at different stages are so definite that one with a little ex-
perience may diagnose the exact sexual stage of the animal
concerned solely by an examination of the smear.
A photomicrograph from a smear of the vaginal content dur-
ing the first stage of mucous secretion is shown by figure 1.
This mucous fluid is seen to contain an abundant mass of cells
which, as shown in the figure, are of a squamous type with very
small pycnotic nuclei sometimes broken into pieces. The cell
protoplasm is also greatly degenerated having only a weak
affinity for the plasma stains and exhibits a reticular structure.
These cells derived from the wall of the vagina (fig. 17) char-
acterize by their presence and great superiority in numbers this
first stage. There are, however, to be seen particularly toward
the end of the first stage a certain number of elongate, cornified
vells without nuclei, which are desquamated from the more
external portions of the vagina. These cells contrast in appear-
ance with the first type cells since in smears stained with haema-
toxylin and eosin they present a decidedly red color, while the
abundant first type cells are almost grey. The red cells rather
DIOESTROUS CYCLE IN THE GUINEA-PIG 239
serve to indicate an intermediate period between the first and
second stages or periods of the flow, and may really be found
during both stages but particularly at the end of the first and
beginning of the second stage. In addition to these two kinds
of cells other types may also be found in a first stage smear but
they are never present in such abundance nor are they so typical
as the two just mentioned. All of the cells float freely in the.
mucus without assuming any definite arrangement.
During the second stage the vaginal fluid is filled with enor-
mous numbers of cells which cause the cheese-like consistency
of the discharge at this time. These cells illustrated by the
photomicrographs, figures 2, 3 and 4 at three different magnifi-
cations, are derived from the upper portions of the vagina with a
few from the uterus and they maintain to a higher degree the
original or healthy architecture of an epithelial cell. The nuclei
are fairly well preserved showing only slight signs of degenera-
tion. The protoplasm has not greatly deteriorated and gives a
good staining reaction thus differing from the grey-staining first
stage cells. The cells are present in innumerable quantities
forming the thick cheesy substance while the mucous secretion
diminishes more and more until it almost disappears. This stage ~
is of short duration.
The third stage begins with the liquefaction of the cheesy mass.
A microscopical examination shows that the cells of the second
stage become less and less numerous, while a great number of
polymorphonuclear leucocytes appear among them (figs. 5 and
6). When the end of this process is reached almost every one
of the cells has become isolated from others of its kind and lies
in the midst of a number of leucocytes. The apparent action or
effect of the leucocytes is to dissolve or digest the desquamated
epithelial cells and this dissolving effect is not only noticed on
cells surrounded by the leucocytes but in some cases the leuco-
cytes dissolve their way into the interior of the cell-bodies (figs.
7 and 8). ‘These appearances are not due, as might possibly be
supposed, to the cells having devoured the leucocytes. This
destructive influence of the leucocytes begins, as will be de-
scribed later, before the desquamated epithelial cells have fallen
240 CHARLES R. STOCKARD AND G. N. PAPANICOLAOU
away from the wall of the uterus and vagina (figs. 15, 16 and 17).
But it probably continues also after the cells are free in the lumen
of the vagina. The dissolving power of the leucocytes, which
probably causes the liquefaction of the cheesy mass of epithelial
cells is shown very well when leucocytes are seen within a cell
and the nucleus is beginning to dissolve. The nucleus is appar-
ently digested and dissolved by coming in contact with the
leucocyte without being at all engulfed or enclosed within the
smaller body of the leucocyte.
As the third stage appoaches its end the material within the
vagina is a thin fluid containing a great number of leucocytes
as well as many epithelial cells of the second stage some of which
contain leucocytes within their bodies. Such leucocyte con-
taining cells are strikingly typical of the third stage. The
leucocytes within these cells as would be expected very soon
show signs of degeneration never staining so clearly as the free
outside ones.
The fourth stage shows the same condition as the preceding
but often at this time a slight hemorrhage takes place, though
this does not always occur. A microscopical examination of the
hemorrhagic fluid shows in addition to the great number of red
blood corpuscles, a large number of leucocytes and also desqua-
mated cells of the second stage, some of which are penetrated by
leucocytes (fig. 9). Sometimes red blood corpuscles are enclosed
within the bodies of the leucocytes and digested, this is probably
a truly phagocytic action and not entirely the same as their
dissolving effect on the neighboring epithelial cells within the
fluid.
The presence of the leucocytes is not alone confined to the heat
period but an abundant quantity of them is also to be found in
the lumen of the vagina during the dioestrum. The only time
that leucocytes are absent from the vaginal lumen is during the
first and second stage described above at the beginning of the
oestrus. Throughout the first week after heat the little fluid
which exists in the vagina contains chiefly leucocytes and a few
atypical desquamated cells. During the second week the num-
ber of epithelial cells increases more and more and among these
DIOESTROUS CYCLE IN THE GUINEA-PIG 241
atypical cells there may exist isolated cells of the first or of the
second stage type.
At the fourteenth and fifteenth day the number of first stage
cells already described begins to increase gradually and the
growing proportion of these cells indicates the approaching new
period of heat.
5. THE OESTROUS RHYTHM
The periodical return of a typical flow showing the above de-
scribed macroscopical and microscopical details, was found to be
very regular in twenty-six virgin females examined during dif-
ferent seasons of the year. Table I shows the results of this ex-
amination. As this table indicates, all the females examined
were virgin thus eliminating any chance of modification which-
might be due to the act of copulation. Their ages ranged be-
tween three and a half and fifteen and a half months during the
time of examination. The female guinea-pig is sexually mature
at about three months old. Almost every animal, as the table
shows, was examined for a length of time covering several oestrus
periods. In the sixty-seven periods examined altogether the
vaginal flow returned regularly every fifteen to seventeen days
with an average of 15.73 days interval between the beginning of
periods.
This table contains nine oestrus periods for operated animals
from which one ovary was removed. The operation was done
to determine whether any decided alteration in the oestrus would
result after the loss of one ovary. The animals 108092 and
1102 2 were semi-spayed during the time of examination given
in the table. In the animal 1080 @ the first heat period follow-
ing operation came at the sixteenth day after the last period but
in the animal 11029 the first heat period following operation
came on the fourteenth day after the last heat, a little earlier
than it should come inder normal conditions. The three heat
periods following this came, however, very regularly every
sixteenth day.
The animals 8672, 92392, and 106992 were semi-spayed a
considerable time before the beginning of the examination and
STOCKARD AND G. N. PAPANICOLAOU
R.
CHARLES
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DIOESTROUS CYCLE IN THE GUINEA-PIG 243
all of these showed an interval of seventeen days between the
beginnings of the dioestrous cycles. The average of seven periods
in animals with only one ovary is 16.57, this bemg much higher
than the average of all the cases, which is 15.73 days. The aver-
age of the only two cases of first heat-periods after operation, on
the other hand, is lower than the general average 15.0. The num-
ber of cases is, however, entirely insufficient to warrant a con-
clusion, though suggestive for further investigation. It is prob-
able that when only one ovary exists, the period between ovula-
tions is a little longer than under normal conditions. The two
ovaries may alternate to a certain degree in their function or they
may share the entire task in a less exhaustive way than one
ovary is capable of doing. Semi-spayed females often have
large litters which might indicate that the single ovary matured
more follicles than would have been its share should the other
ovary have been present.
Eliminating from the general table the results obtained by the
examination of the semi-spayed animals, one finds an ayerage of
15.65 days for the length of time from the beginning of one heat
period to the beginning of the next in all normal cases. This
we believe to be the length of the oestrous cycle of the guinea-pig
under uniform conditions.
Table 1 further shows the months during which these observa-
tions were made. The animals were examined during early
summer, fall, winter and spring and have shown at all seasons a
perfect regularity in the return of the heat periods. Their
oestrous cycle is certainly typically regular. The only months
during which the animals were not examined are July, August
and September. During the winter the guinea-pigs are kept
in a fairly well regulated warm temperature running about 70°
Fahrenheit on an average. It may be possible that in the
wild state under natural conditions when the weather is cold
and food somewhat scarce, the heat periods may cease for a
season or become less frequent. Rubaschkin claimed that heat
ceased to recur after October when guinea-pigs were kept in a
cold place. But under the steadily favorable conditions in
which the guinea-pigs here considered are kept, it is certain that
244 CHARLES R. STOCKARD AND G. N. PAPANICOLAOU
they are sexually active throughout the entire year with an
astonishingly regular return of their oestrous flow and breeding
reactions.
A more careful consideration of the figures obtained during
the different months indicates, however, that there probably is a
small difference in the length of the sexual cycles during the warm
and the cold seasons.
The curve shown in figure A indicates graphically this slight
fluctuation, operated animals are excluded. The lowest aver-
age 15.50 days, or the shortest oestrous cycles, was found in the
month of October, while the highest 16.14 days is shown during
January. The heavy line at 15.82 days indicates the mean
between these two extremes. It is probably not without sig-
nificance that the averages during the months December, Jan-
uary, February, March and April fall above the mean line,
while the averages during the months of May, June and October
are below the line. From the cases considered this indicates
that the length of the oestrous cycle is probably a little shorter
during the warm time of the year and a little longer during the
cold weather. We must, however, admit that the number of
considered cases, as given in table 1, is actually small and these
slight seasonal variations may be more suggestive than demon-
strative in importance, yet there is certainly a striking consistency
in their arrangement.
6. CYCLICAL CHANGES IN THE UTERUS AND VAGINA
After having determined the regularity of the dioestrous cycle
in a number of virgin females, they were killed at different stages
of the oestrous period and their ovaries as well as pieces of the
uterus and vagina were carefully examined and then fixed and
preserved for microscopical study. The uterus and vagina
must be fixed in certain fluids to avoid shrinkage and a tearing
away of the epithelium from the wall. Bouin’s fixing fluid has
proven most satisfactory for this purpose while the ovaries were
generally fixed with Zenker’s fluid.
During the dioestrum or resting period the uterus is lined by a
layer of cuboidal ciliated epithelium. Figure 10 shows a sec-
245
DIOESTROUS CYCLE IN THE GUINEA-PIG
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246 CHARLES R. STOCKARD AND G. N. PAPANICOLAOU
tion through the uterus at four and a half days after the last
oestrus. At this time the epithelial cells present a normal and
vigorous aspect. No loss or breaking down is to be noticed. <A
few leucocytes are occasionally seen among the cells of the
stroma, but never in large numbers. Mitoses are not frequent
at this time but they are to be seen now and then.
When the heat period begins, the epithelium loses its normal
appearance (figs. 11, 12 and 13). The epithelial cells become
tall and columnar and are filled with mucus which they begin
to form in abundant quantity The nuclei of the columnar
cells appear closely pressed one against the other and are pressed
into different levels in the various cells so as to give an appear-
ance of several rows of nuclei. The epithelium thus takes on a
pseudo-stratified arrangement. At the same time, a large num-
ber of leucocytes begin to migrate from the capillaries through
the stroma and towards the epithelium. The stroma itself is
congested and possesses a more profuse circulation than usual.
These appearances are to be seen in animals killed during the
first phase of their period, that is, when the vagina contains an
abundant mucous fluid filled with desquamated epithelial cells.
A smear of this fluid is illustraed in figure 1.
As soon as the second phase of the vaginal fluid appears (figs.
2, 3 and 4), the uterus shows another aspect. The leucocytes are
accumulating in large numbers below the epithelium, forming in
some places a perfect wreath of leucocytes under the epithelium
or actually a separate layer of cells (fig. 14). The stroma shows
a more advanced degree of congestion.
During the third stage, smears figures 5 and 6, the leucocytes
penetrate more and more into the epithelium some of them mak-
ing their way into the lumen of the uterus by passing between the
epithelial cells. Other leucocytes actually enter the epithelial
cells and penetrate into their interior (fig. 15). A stage more
advanced in appearance corresponding to a late third stage
though from the same animal as figure 15, is shown in figure
16, where the entire epithelium is almost completely disintegrated.
A great number of leucocytes has already penetrated the epithe-
lium the cell structure of which has become largely destroyed.
DIOESTROUS CYCLE IN THE GUINEA-PIG 247
Large vacuoles are to be seen between the epithelial cells, and
these are probably produced by the dissolving power of the
leudocytes. Under the destroyed epithelium haematomata are
to be seen in several places, produced by the congestion of the
peripheral capillaries in the stroma. A leucocytosis somewhat
similar to the above has been described by Heape, Konigstein,
Blair-Bell and others in the uteri of several mammals.
The vagina of the guinea-pig also shows analogous conditions
as illustrated in figure 17.
The broken down epithelium remains until the regeneration
process begins. The reparation starts from the necks of the
uterine glands which have remained intact during the entire
process of destruction. A few leucocytes are to be seen be-
tween the epithelial cells of the uterine glands but this small
number apparently passes through the epithelium into the duct
without injuring the epithelial cells. The stage of reparation
corresponds to the fourth stage, that is, to the period when blood
is sometimes seen in the vaginal fluid, see smear figure 9. This
is not difficult to explain since regeneration and the falling off
of the degenerated epithelium take place at the same time.
Regeneration of the uterine epithelium before the oestrous flow
had ceased has been reported in other mammals.
After examining a number of specimens, one may get the im-
pression that the new epithelium growing out from the neck of
the glands tends to push off the old degenerate epithelium, as it
becomes detached from the wall of the uterus. Figures 18 and
19 show this condition where the new and the old epithelium
are still existing in close proximity, the one growing out from
the gland, the other breaking away from the wall of the uterus.
In figure 19, this condition is more advanced and one sees the
old epithelium partly detached from the wall of the uterus.
Generally the epithelium falls off still connected with pieces of
the stroma, which also seems to be destroyed to some extent
during every heat period. These masses of epithelial cells are
commonly found in the vaginal fluid. When the epithelium
falls away the haematomatia are uncovered and the blood con-
248 CHARLES R. STOCKARD AND G. N. PAPANICOLAOU
tained in them passes into the lumen of the uterus. A similar
bleeding may also occur into the lumen of the vagina.
The regeneration of the mucosa seems to take place very
quickly. About six to ten hours after the above stage the new
epithelium is already completely formed. The growth of the
new and the falling off of the old epithelium seem to go hand in
hand, so that no stage is to be found when the uterus is com-
pletely unlined by its epithelial layer. However, one may occa-
sionally observe, during the above described fourth stage, lim-
ited naked regions from which the old epithelium has been
detached before the new has formed.
The wall of the vagina undergoes somewhat the same de-
structive changes as the wall of the uterus except that the des-
quamation of the vaginal epithelium does not occur in cell
clumps or groups at the end of the third stage. The vagina
merely sheds its epithelial cells singly but in increasing num-
bers from the beginning of the heat period up to the third stage.
The desquamation appears to proceed from near the entrance
up into the inner portions of the vagina. The cells which ap-
pear during the first stage come from near the outer part of the
vagina, while during the second stage the desquamated squamous
cells are derived from the inner part of the vagina. This state-
ment does not include the cornified cells from near the orifice,
which are found as mentioned above, between the first and
second stages. The vaginal epithelium is also invaded by the
leucocytes. This migration is very vigorous during the third
stage, about the same time as in the uterus. An innumerable
mass of polymorphonuclear leucocytes migrate into the vaginal
epithelium and actually enter its more superficial cells by pene-
trating into their cell bodies (fig. 17).
The beginning of the desquamation before the massive arrival
of the leucocytes shows that the primary cause of the desqua-
mation is not the presence of the leucocytes. But, on the con-
trary it is probably the presence of the altered and dying des-
quamated cells which induces the extensive migration of leuco-
cytes to this epithelial surface. The large epithelial cells of the
vagina photographed in figure 17 are the same cells which are
DIOESTROUS CYCLE IN THE GUINEA-PIG 249
to be observed in the vaginal fluid during the third stage, see
smears figures 6, 7 and 8. A congestion of the capillaries of the
mucosa also takes place in the vagina, and slight hemorrhages
may occur as in the uterus, when the destruction of the stratified
epithelium chances to reach down to the tunica propria.
The leucocytes are chiefly attracted to that portion of the
epithelium covering the outfoldings into the lumen and this part -
undergoes a greater destruction. In a similar way it is the epi-
thelium covering the prominent folds of the uterus which is
destroyed, while the ingrowths which form the uterine glands
are preserved and through regeneration from their necks furnish
the new material which is necessary for the restoration of the
lost epithelium.
During the dioestrum or rest period the desquamation of epi-
thelium from the vagina does not stop completely and the scant
vaginal fluid always contains some desquamated cells. At the
same time, and probably connected with the shedding process
the exodus of the leucocytes also continues though in a less
active way than during heat. The ‘intermenstrual fluid’ there-
fore always contains a considerable number of leucocytes.
7. THE OVARIAN CYCLE
A study of the ovaries fixed during different stages of the
oestrous cycle has shown that every change taking place in the
uterus and the vagina has its corresponding stage of change in
the ovary. At the beginning of the first stage the ovaries
possess large, ripe follicles, figures 20 and 21. The nuclei of the
eggs contained in the follicles are in a resting condition. The
theca folliculi shows the beginning of a slight congestion. As
the first stage advances this congestion becomes more and more
pronounced and by the beginning of the second stage it is highly
developed, figures 22 and 23. This extreme congestion of the
theea folliculi, which exist at about the same time as the con-
gestion stage in the uterus (cf. fig. 14) indicates that the follicle
is ready for rupture. Heape has pointed out that the rup-
ture of the follicle is due to this congestion and if the ovarian
THE AMERICAN JOURNAL OF ANATOMY, VOL. 22, NO. 2
250 CHARLES R. STOCKARD AND G. N. PAPANICOLAOU
blood supply be tied off follicles do not rupture. During this
time the nucleus of the egg is still in a resting condition.
The ripe follicles break at about the end of the second or the
beginning of the third stage. Figure 24 shows a follicle just
broken at the commencement of the third stage. It will be re-
called that at this time the active leucocytosis begins in the
uterus and the vagina, compare figures 15, 16 and 17. The
ovaries are not omitted from this active migration of the leuco-
cytes. A number of leucocytes are to be seen in the corpus
luteum during its early development, but great numbers of
leucocytes are to be found mainly in the atretic follicles, which
are now becoming the seat of regressive and degenerative pro-
cesses (fig. 25). The eggs in these disorganizing follicles show a
peculiar activity expressed by the formation of the maturation
spindle. Most of the eggs begin to degenerate before the forma-
tion of a polar body, though some of them succeed in completing
their maturation divisions. Figure 25 shows an egg within a
disintegrating follicle, the follicle containing a great number of
leucocytes. This egg possesses a well formed polar body in the
process of division. Kirkham has reported similar conditions
in the ovary of the mouse, he notices that eggs degenerate after
forming the first polar body and the second polar spindle, a con-
dition closely similar to that shown in our figure 25. The
outline of the polar body is clearly shown in the specimen.
The photograph is not ‘touched up.’
The chromatin of the nucleus is to be seen in the center of the
egg in figure 25. In all the cases observed, the eggs of the
atretic follicles degenerated, the nucleus breaking up into irregu-
lar pieces very soon after ovulation had taken place from the
ruptured follicles. We failed to find anything to indicate a
tendency toward parthenogenetic divisions in the many speci-
mens which we have examined as Leo Loeb reported for these
animals.
The ruptured follicles very quickly begin to undergo a reor-
ganization resulting in the formation of the corpora lutea. Even
during the third stage the corpus luteum is a well circumscribed
body beginning its differentiation by the ingrowth of the vascular
DIOESTROUS CYCLE IN THE GUINEA-PIG PAS
tissue of the theca folliculi into the hypertrophied follicular epi-
thelium (fig. 26). This condition is more advanced during the
fourth stage, when reparation begins in the uterus. Figures 27
and 28 illustrate two corpora lutea from the same ovary during
the stage of uterine hemorrhage, the two are cut in different
directions. The ingrowth of the vascular tissue toward the cen-
tral cavity is apparent in these two figures. A well formed
mature corpus luteum is shown in figure 29, taken from a sec-
tion through the ovary of an animal about four and a half days
after the heat period when the uterus was in a typical resting
condition (fig. 10).
8. GENERAL CONSIDERATIONS
After a review of the above described facts there are several
problems of general importance which may be profitably dis-
cussed in connection with them.
A fact of considerable significance is that the development
and the degeneration of the uterine and vaginal mucosa corre-
sponds very closely to the development and degeneration of the
corpora lutea in the ovaries. At the time when the corpora lutea
are highly developed and apparently active the mucosae of the
uterus and vagina show a normally vigorous and healthy con-
dition (cf. figs. 10 and 29). While on the other hand when the
corpora lutea begin to degenerate during the second week after
the ‘heat period’ the mucosae of the uterus and vagina also
begin to show signs of degeneration and the process of desqua-
mation slowly commences. At about two weeks after the last
‘heat period,’ when the wholesale destruction of the mucosa
begins, the corpora lutea are almost completely degenerated.
The breaking of the Graafian follicles occurs during the oestrus
as a result of a congestion which began in the theca folliculi at
about the same time as the congestion of the stroma of the uterus
and vagina. And finally when the regenerative growth of the
uterine mucosa sets in, the ovaries then possess new corpora lutea
in an active state of differentiation which were derived from
these recently ruptured follicles.
252 CHARLES R. STOCKARD AND G. N. PAPANICOLAOU
These occurrences argue very decidedly against the theory
advanced by Fraenkel (’03), and until recently supported by a
number of other investigators. Fraenkel believed that the
corpus luteum is the cause of the menstrual condition, producing
through its secretion the destructive changes in the uterus and
vagina. Such a supposition does not in any sense accord with
the phenomena as they appear in the guinea-pig. If there is to
be ascribed to the secretion of the corpus luteum an action upon
the uterine and vaginal mucosae such an action is not of an in-
jurious but of a protective nature. As we shall bring out further,
the most plausible opinion of the action of the corpus luteum in
the ovary itself, may also be interpreted as of a protective nature
since it seems to prevent rupture of the Graafian follicles and the
discharge of the ova. The facts obtained in the present inves-
tigation might not fully warrant the position that the corpus
luteum really exerted an actively protective influence over the
uterine mucosa, but they certainly in no sense suggest, and actu-
ally speak against, any injurious action on the mucosa by the
secretion of the corpus luteum.
At the same time it is difficult to maintain that the absence of
the protective action of the corpus luteum is the only or actual
cause of the oestrous activity. The cause of oestrous is very
probably more complex and the definitely regular rhythmical
changes which take place in the uterus and vagina of the guinea-
pig can not be fully explained as due alone to the degenéra-
tion of the corpus luteum. The absence of the luteal secretion
possibly merely permits the uterine flow to occur as it seems also
to permit the rupture of the ripe Graafian follicles. While the
real mechanism determining the uterine reaction is a more
complex factor and relatively independent, but affected in its
expression by a close inter-relationship with the ovaries.
The various theories, however, which attempt to localize the
cause of the uterine changes in the ovary are not in any case fully
in accord with all the facts. It is of course true that the existence
of the ovaries is necessary for the normal development and
function of the uterus and vagina, and also that the removal of
both ovaries leads to a disappearance of the typical oestrous
DIOESTROUS CYCLE IN THE GUINEA-PIG Doe
changes in the uterus and finally to a degeneration of this organ.
Yet the complete removal of the ovaries does not always pre-
vent the menstrual periodicity from expressing itself in an
atypicl but regular way for a considerable time afterwards
(see Halban).
Our observations on three females from which both ovaries
have been completely removed, show that such an operation
does not fully abolish the return of the destructive menstrual
changes as is generally claimed. But on the other hand, the
absence of the ovaries promotes and prolongs the continuation of
these destructive changes in such a way, that instead of a periodi-
cal menstruation, these spayed females have a long, continuous
and atypical destruction of the uterine and vaginal mucosae,
which leads finally to the degeneration of these organs. In some
cases a distinct periodicity may be perceived, indicating that the
rhythm of the menstrual activity may exist independently of
the ovaries. ‘The phenomenon that really is abolished and absent
from the uterus after the removal of the ovaries is the return of
any regenerative or reconstructive process which we believe is
normally due to a secretion from the newly formed corpora
lutea.
From such a view of these phenomena one may draw the fol-
lowing general conclusions: The oestrous changes in the uterus
are regulated by two different factors, one direct and the other
indirect. A secretion elaborated in the ovary apparently by the
corpus luteum is necessary for the normal development and per-
sistence of the uterine and vaginal mucosae. The absence of
the secretion leads to regression and degeneration of the uterine
tissue. Yet this control is not the entire explanation of men-
struation. The regulation of this process and the return of defi-
nite changes in definite periods of time may possibly be due to
the existence of a fixed mechanism somewhere outside the ovary.
The role of the ovary and especially of the corpus luteum is not
to produce but to permit and to stop the menstruation. Our
conceptions correspond completely with the ideas of Halban,
who has recognized the protective réle of the ovaries upon the
254 CHARLES R. STOCKARD AND G. N. PAPANICOLAOU
uterus and the vagina and the existence of a separate causal
factor of menstruation independent of the ovary.
Fraenkel’s theory that the corpus luteum is an active factor
producing menstruation does not correspond with our observa-
tions. Neither, on the other hand, does the assertions of
Marshall and Runciman that ‘“‘the corpora lutea evidently exert
no influence on the occurrence of heat’? seem to us justified.
Marshall and Runciman (’14), have advocated the importance
of the interstitial cells in considering the ovarian factor con-
cerned in the recurrence of the oestrous cycle as opposed to any
active effect of the corpora lutea. They point out the evident
incorrectness of the old views that the ovaries and uterus are
related by a nervous connection. ‘Transplantation experiments
have shown the fallacy of such a notion and have demonstrated
the presence of an internal secretion from the transplanted
ovarian mass. Marshall then in arguing against the importance
of the corpus luteum uses Heape’s (’97), observations which
showed that in monkeys menstruation might take place in the
absence of either ripe follicles or newly formed corpora lutea.
This observation, it seems to us, does not in any way point
towards the interstitial cells as being important. Nor does it
argue against our view that the absence of the corpora lutea
permits menstruation and that their presence exerts a protective
influence over the uterine mucosa. Heape’s observation is per-
feetly in accord with this and it is to be expected that corpora
lutea should be either degenerate or absent when menstruation
occurs.
Marshall and Runciman performed operation experiments on
tour bitches. At these operations they attempted to destroy the
large Graafian follicles by pricking with a knife or needle. In
the first fox terrier at least nine follicles were injured in this
manner. But one who has operated on the dog’s ovaries knows
how difficult it would be to discover all of the ripe follicles and
almost impossible to get those on the dorsal surface of the ovary
which is often closely bound down and almost covered. Yet
it is not necessary in this discussion to question the destruction
of every ripening follicle since the photomicrographs, which the
DIOESTROUS CYCLE IN THE GUINEA-PIG PASTS
authors publish, show that corpora lutea formed after the rup-
ture of the follicles, and they state that the follicles artificially
ruptured changed ‘“‘into structures almost identical with normal
corpora lutea’’—except that development was not sufficient to
fill the central cavity.
In the first two animals, which were their best experiments,
since the time of the expected ‘heat period’ was fairly accurately
known, the ‘heat’ came on about the time, or perhaps a little
later, than it was expected and was not greatly influenced by the
operation. This is just what we should expect on our supposi-
tion of the function of the corpora lutea. The dog is a mon-
oestrous animal with a long anoestrous period and the destruc-
tion of Graafian follicles a few weeks before the oestrus was
expected would have no bearing on the probable function of the
corpora lutea in bringing on this period. The old corpora lutea
resulting from the last ovulation were not disturbed and were
probably just about degenerating and thus permitted the oestrus
to occur very near the normal time. While the newly formed
corpora lutea resulting from the operation were not sufficiently
vigorous in their action to do more than slightly delay the
menstruation.
Marshall and Runciman concluded that it is evident that the
occurrence of ‘heat’ in the dog is not dependent upon corpora
lutea, and that ‘‘The ovarian interstitial cells are possibly con-
erned in the process, but cyclical changes in the condition of
these cells have not so far been observed in the dog’s ovaries.”
These conclusions and Marshall and Runciman’s discussion
are directed chiefly against Fraenkel’s idea regarding the way in
which the corpora lutea act; that is, the corpora lutea by their
secretion perform an active function in bringing on the oestrous
condition. We also disagree on the basis of the evidence fur-
nished by the guinea-pigs with Fraenkel’s views and for these
animals at least such opinions are entirely incorrect. It seems
to us, however, that Marshall and Runciman’s experiments do
not in any way argue against the position that the corpora lutea
exert a protective influence over the uterine mucosa, nor that
the absence or degeneration of the corpora lutea and the dis-
256 CHARLES R. STOCKARD AND G. N. PAPANICOLAOU
appearance of its secretion permits the uterine mucosa to
undergo the degenerative changes typical of the ‘heat period.’
Therefore, we must object to their conclusion that the occur-
rence of heat is not dependent upon corpora lutea—and further
we are unable to believe that their experiments, or any other so
far recorded, indicate that ‘‘the ovarian interstitial cells are
possibly concerned in the process.’’ The evidence to our minds
does not in the least point in such a direction.
A most ingenious attempt at an explanation of menstruation
and one of the first logical views regarding the function of the
corpus luteum was advanced twenty years ago by Beard’in his
monograph on the ‘Span of gestation and the cause of birth.’
According to Beard ‘‘Menstruation is comparable to an abor-
tion prior to a new ovulation, and it is an abortion of a decidua
prepared for an egg which was given off subsequent to the
preceding menstrual period, and which had escaped fertilization.”
In the earlier mammals, Beard imagines that gestation ex-
tended over only one ovulation period or short dioestrum of
Heape’s terminology. Thus prior to each ovulation, a birth
would take place provided pregnancy had ensued after the pre-
vious ovulation, and if not the ovulation would be preceded by
an abortive birth act. In this connection it is interesting to
recall the well known fact that in man and other mammals
abortions occur with a far greater frequency at the times for
regular menstrual periods than at other times. In the human
the time of the first menstruation after conception is a most
critical period, and the time when the third menstruation
should occur is responsible for the great predominance of three
month foetuses to be seen in most collections, and so on up to
the tenth period when the normal birth takes place.
In the evolution of mammals Beard calls attention to the tend-
ency to develop a longer gestation period and more fully devel-
oped offspring, but in all cases the length of the gestation period
is a multiple of the primitive ovulation periods. A reminis-
cence of the earlier primitive conditions still exist in all of the
polyoestrous mammals. The gestation period of the guinea-pig
extends over four oestrous cycles making it about sixty-two days
long.
DIOESTROUS CYCLE IN THE GUINEA-PIG PAST
During pregnancy in higher forms, according to Beard’s
scheme the corpus luteum exerts a protective function by pre-
' venting a new ovulation and an abortive birth. In non-preg-
nant females, however, this abortive process is not counteracted
by the quickly degenerating corpus luteum spurium and the
uterus undergoes the changes of menstruation and a new ovula-
tion occurs. This ingenuous theory aims to furnish an expla-
nation of the periodically: destructive changes occurring in the
uterus and vagina of some mammals at the same time that the
ovary is preparing to liberate its ova. And the chief virtue
of the theory is that it points out the protective action of the
ovary and especially of the corpora lutea on the uterine mucosa.
Every menstruation process and every abortion reflex as well as
every normal birth is the result of two different factors, one the
condition produced by the absence of the luteal secretion and the
other is the expression of a phylogenenetically and physiologi-
cally fixed rhythmical tendency within the uterus itself.
Beard’s conception of the corpus luteum as an organ preventing
ovulation has been adopted and further developed by many .
later investigators, Prenant, Sandes and Skrobansky, Leo Loeb,
Ruge, Pearl and Surface, Halban and Kohler and others. All
of these investigators have added evidence in favor of Beard’s
corpus luteum theory partly by new observations and partly by
experiments on the living animals.
To state Beard’s (98, p. 101) position in his own words:
The corpus luteum is probably a contrivance for the supression or
rendering abortive of ovulation during gestation. The commencing
degeneration of this structure some little time before the end of the
gestation (like its rapid atrophy where fertilization has not taken
place) allows of preparation being made for a new ovulation.
We are indebted to Leo Loeb (11), for first putting these
conceptions of Beard to experimental test. And Loeb showed
that pregnancy as such does not prevent ovulation if corpora
lutea are extirpated from the ovaries. Loeb also destroyed the
corpora lutea in non-pregnant guinea-pigs and later examined
the ovaries after different periods of time. In forty-two females
the corpora lutea were destroyed by cutting them out completely
258 CHARLES R. STOCKARD AND G. N. PAPANICOLAOU
with the following results: In one case the next ovulation had
already occurred at the twelfth to thirteenth day (by the next
ovulation is meant the ovulation following the last copulation)
in one case at the thirteenth day, in five cases at the thirteenth
to fourteenth day, in twelve cases at the fourteenth to fifteenth
day, in four cases at the fifteenth to sixteenth day, in one case
at the sixteenth to sixteenth day and a half, in one case at the
sixteenth to seventeenth day, in one’ case after eighteen days,
while in eight cases ovulation had not yet occurred at the time
when the animals were killed.
Loeb also cauterized the corpora lutea in the ovaries of thirty-
one guinea-pigs but the results, owing to the inferiority of this
method, were not so satisfactory. The ovulation in some cases
came at the fourteenth to fifteenth day, in other cases later.
Loeb interpreted these experiments to indicate that the removal
of the corpus luteum hastened the next ovulation. Such a con-
- clusion is in no way actually contradicted by our observations,
yet the experiments of Loeb are not completely satisfactory in
the light of the present findings Loeb thought the usual
sexual period, or time between two ovulations, in the guinea-pig
was very much longer, and much more variable than it actually |
is. On such a basis it seemed that the ovulation period in the
animals he examined had been considerably reduced. But as
the present study shows the normal oestrous cycle in the guinea-
pig is from fifteen to seventeen days, usually about sixteen
days with very insignificant variations. So that the periods re-
corded by Loeb, after the operations are actually just about of
normal duration. He found the greatest number of cases to
ovulate after a period of fourteen to fifteen days (12 such cases
or 28.57 per cent) and considered this much shorter than the
normal condition, where as a matter of fact such a period differs
only insignificantly from what we find to be the regular length
of the oestrous cycle.
When we also take into account his method of calculating the
days between the last copulation and the next ovulation, and
especially the fact that he figured the ovulation time by the
condition and probable age of the newly formed corpora lutea
DIOESTROUS CYCLE IN THE GUINEA-PIG 259
found in the ovaries examined, the slight variations are all very
probably within the limits of error. We also believe that Loeb
has been misled by the application of similar methods in caleu-
lating the normal sexual periods in these animals.
In order to test the influence of the removal of the corpora
lutea on the following ovulation time, one must first definitely
establish a normal ovulation period. Since this was not done we
are forced to acknowledge that Loeb’s experiments do not
demonstrate the importance of the corpus luteum in regulating
the ovulation process, though he must be credited for having
definitely attacked the problem experimentally. Some doubt
will also exist in the minds of those who have attempted the
operation as to whether all of the corpora lutea are often to be
removed from the ovary while it is in position in the abdomen.
We are not at all opposed to admitting the probability that the
removal of the corpus luteum may shorten the usual sexual cycle.
In fact such a discovery would accord with our notions of the
function of the corpus luteum. We feel further that the present
study has established the existence of a definite normal oestrous
cycle and this knowledge makes the experimental analysis of the
influence of the corpus luteum much more readily approached.
The knowledge of a typical and regular sexual cycle in the
guinea-pigs as here demonstrated, paves the way for a better
and more uniform understanding of the oestrous conditions pre-
vailing in the different classes of mammals. All cases that have
been studied with sufficient care give evidence at least of some
rhythmical activity. The absence of external signs of oestrus
in a great number of mammals, one of which was the guinea-pig,
is the most evident cause of a lack of understanding of their
sexual periodicity. It is to be hoped that the application of the
simple method of examination of the vaginal fluid used in the
present study may enable workers to readily obtain a clearer
understanding of the sexual activities of other commonly used
laboratory animals as well as mammals in general, since such
information is of the greatest value in all exact experimental
breeding.
260 CHARLES R. STOCKARD AND G. N. PAPANICOLAOU
The typical oestrous cycles are probably more regularly ex-
pressed among mammals living in a state of domestication, and
consequently under steady environmental conditions, than
among their relatives living in the wild, where the existence of
great disturbing factors, especially variations in food and tem-
perature conditions, may tend to modify their behavior. The
evidence of such modification by these disturbing factors is the
existence in most mammals of differences in their sexual be-
havior during the different seasons of the year. Such seasonal
variations are frequently lost under uniform conditions of tem-
perature and feeding as is the case with rabbits, and also with
guinea-pigs if these show seasonal changes in their native wild.
It has been reported by some investigators, Rubaschkin and
others, that guinea-pigs in captivity breed less frequently in
winter than during the warmer months, though they may be-
come pregnant at any season. Such results are probably due
to a failure to keep the animals properly warm during winter.
Guinea-pigs under the uniform conditions of our experiments
do not show any apparent changes in their sexual rhythm with
_ the seasons, but as indicated on previous pages, it is probable
that their sexual cycle is a little shorter during the summer than
in winter, yet even this difference does not seem to be very
definitely expressed.
9. SUMMARY
The above description of the details of the oestrous cycle in
the guinea-pig may be briefly summarized as follows:
1. Guinea-pigs kept in a state of domestication and under
steady environmental conditions possess a regular dioestrous
cycle repeating itself in non-pregnant females about every six-
teen days throughout the entire year with probably small and
insignificant variations during the different seasons.
2. During each cycle typically corresponding changes are
occurring in the vagina, the uterus, and the ovary; a given stage
in one of these organs closely accompanying parallel stages in
the other two.
3. Each period of sexual activity lasts about twenty-four
hours and is characterized by the presence of a definite vaginal
DIOESTROUS CYCLE IN THE GUINEA-PIG 261
fluid, which is not sufficiently abundant to be readily detected
on the vulva but is easily observed by an examination of the
interior of the vagina.
4. The composition of the vaginal fluid changes with the
several stages of change occurring in the uterus and vagina.
a. To begin with, during what we term the first stage, the
fluid consists of an abundant mucous secretion containing great
numbers of desquamated vaginal epithelial cells. At this time
sections of the vagina show an active shedding or desquamation
of its epithelial lining cells. The cells of the uterine epithelium
are loaded with mucus, and an active migration of polynuclear
leucocytes is taking place from the vessels of the vagina and
uterus out into the stroma and towards the epithelial layer.
b. During the second stage the contents of the vagina become
thick and cheese-like on account of the great accumulation of
desquamated epithelial cells. The walls of the uterus and:
vagina become congested and the migration of leucocytes becomes
still more active.
c. The leucocytes reach the epithelium and vigorously invade
its cells and intercellular spaces during the third stage. These
wandering cells become enclosed within and apparently dissolve
the breaking-down dead cells of the epithelium. The vaginal
fluid becomes thinner under the dissolving or digesting action
of the leucocytes. The congestion in the uterus and vagina
becomes still more pronounced giving rise to small blood masses
or haematomata beneath the epithelium. The epithelium of the
uterus is highly disorganized, vacuolized and richly invaded by
the leucocytes, so that portions of it tall away en masse actually
carrying with it in some cases cells of the stroma.
d. The fourth stage is merely a continuation or result of the
activities of the third. The falling away of the epithelial pieces
and stroma cells permits the escape of the small haematomata
or blood knots thus causing a slight bleeding into the lumen of
the uterus and vagina. These traces of blood often give a red-
ish aspect to the vaginal fluid. At this same stage a regenera-
tion process begins from the necks of the uterine glands and also
apparently from the epithelial infoldings in the vagina, so that
262 CHARLES R. STOCKARD AND G. N. PAPANICOLAOU
the lost epithelium becomes rapidly replaced almost before it
has ceased falling away. If one may picture the epithelial sur-
face of the uterus and vagina as consisting of innumerable promi-
nences and depressions, it may be said that the destructive proc-
esses mentioned above are largely confined to the epithelium
covering the prominences and that this epithelium is finally
restored by regeneration from the epithelium lining the depres-
sions, or in the case of the uterus from the epithelium of the
uterine glands. The congestion with the diapedesis of cor-
puseles and the formation of the blood haematomata and the
great accumulation of leucocytes all occur chiefly in the out-
pushed or protruding parts of the uterine wall.
The regeneration process in the guinea-pig is very short, last-
ing only a few hours, from six to twelve in all.
5. Ovulation seems to occur spontaneously during every heat
period without exception. The rupture of the follicles with the
consequent ovulation takes place about the end of the second
stage or the beginning of the third; that is, during the presence
of the thick cheese-like vaginal fluid.
6. During the dioestrum or intermenstrual period there is very
little fluid to be found in the vagina. This scant fluid consists of
mucus in which are some atypical squamous cells from the
vaginal wall and many leucocytes. A number of the leuco-
cytes are old but there are probably new ones arriving almost
continuously from the wall of the vagina. The only time at
which the vagina seems to be practically free of leucocytes is
immediately before and during the first and second stages of the
oestrous period described above.
7. A marked correlation exists between the oestrous changes
in the uterus and the developmental cycle of the corpora lutea.
When the corpora lutea are highly developed and apparently
active the mucosae of the uterus and vagina show a normally
vigorous and healthy condition. While, on the other hand,
when the corpora lutea begin to degenerate during the second
week after the ‘heat period’ the mucosae of the uterus and
vagina also begin to show signs of degeneration and the process
of desquamation slowly commences. At about two weeks after
DIOESTROUS CYCLE IN THE GUINEA-PIG 263
the last ‘heat period,’ when the wholesale destruction of the
mucosa begins, the corpora lutea are almost completely degen-
erated. The breaking of the Graafian follicles occurs during the
oestrus as a result of a congestion which began in the theca
folliculi at about the same time as the congestion of the stroma
of the uterus and vagina. And finally when the regenerative
growth of the uterine mucosa sets in, the ovaries then possess
new corpora lutea, in an active state of differentiation, which
were derived from the recently ruptured follicles.
It, therefore, might be imagined that the secretion from the
corpora lutea exerts a protective influence over the uterus and
vagina while the absence of this secretion permits the breaking
down and degeneration of the uterine epithelium typical of the
‘heat period.’
264 CHARLES R. STOCKARD AND G. N. PAPANICOLAOU
10. LITERATURE CITED
Bearp, J. 1897 The span of gestation and the cause of birth. A study of the
critical period and its effects in mammals. Fischer, Jena.
1898 The rhythm of reproduction in mammalia. Anat. Anz., vol. 14.
Biscuorr, To. L. W. 1844 Beweis der von der Begattung unabhingigen peri-
odischen Reifung und Loslésung der Hier der Siugethiere und des
Menschen. Giessen.
1852 Entwickelungsgeschichte des Meerschweinchens. Giessen.
1870 Neue Beobachtungen zur Entwickelungsgeschichte des Meer-
schweinchens. Abh. der Kénigl. Bayer. Akad. der Wissensch., vol. 10.
Buatr-BeLt, W. 1908 Menstruation and its relationship to the calcium me-
tabolism. Proc. Roy. Soc. of Med., Obstet. and Gyne. Sec., July, p.
291.
Bourn, P. et ANcEL, P. 1909 Sur les homologies et la signification des glandes
a sécrétion interne de l’ovaire. C. R. Soc. Le Biol., vol. 67.
1910 Recherches sur les fonctions du corps jaune gestatif. Jour. de
Physl. et de path. génér.
Corner, G. W., AND AMsBAuUGH, A. E. 1917 Oestrus and ovulation in swine.
Anat. Rec., vol. 12. _
FRAENKEL, L. 1903 Die Function des Corpus luteum. Arch. fiir Gynaekol.,
vol. 68.
Haupan, J. 1911 Zur Lehre von der Menstruation—Protective Wirkung der
Keimdriisen auf Brunst und Menstruation. Zentralbl. f. Gynaekol.,
vol. 35.
HALBan, J., UND KOHLER, R. 1914 Die Beziechungen zwischen Corpus luteum
und Menstruation. Arch. of Gynikol., vol. 103.
Heart, W. 1899 The menstruation and ovulation of monkeys and the human
female. Trans. Obstet. Soc., vol. 40. }
1900 The sexual season. Quart. Jour. Mic. Sce., vol. 44.
1905 Ovulation and degeneration of ova in rabbits. Proc. Roy. Soc.
London, vol. 76 B.
HENSEN, V. 1876 Beobachtungen iiber die Befruchtung und Entwickelung des
Kaninchens und Meerschweinchens. Zeit. f. Anat. u. Entwick, vol. 1.
KirkHaM, W. B. 1910 Ovulation in mammals with special reference to the
mouse and rat. Biol. Bull., vol. 18.
Ko6nriesteIn, H. 1907 Die Verinderungen der Genitalsschleimhaut wahrend
der Graviditit und Brunst bei einigen Nagern. Arch. f. Physiol.,
vol. 119.
Lams, H. 1913 Etude de lVoeuf de Cobaye aux premiers stades de l’embryo-
genése. Arch. de Biol., vol. 28.
Lors, L. 1911a Uber die Bedeutung des Corpus luteum fiir die Periodiziti
des sexuellen Zyklus beim weiblichen Siugetierorganismus. Deutsche
Mediz. Wochensch. No. 1.
1911 b The cyclic changes in the ovary of the guinea-pig. Jour.
Morph., vol. 22.
1911 ¢ The cyclic changes in the mammalian ovary. Proc. Am. Phil.
Soc., vol. 50.
DIOESTROUS CYCLE IN THE GUINEA-PIG 265
Lonetey, W.H. 1911 The maturation of the egg and ovulation in the domestic
cat. Am. Jour. Anat., vol. 12.
Marsnatt, F. H. A. 1903 The oestrous cycle and the formation of the corpus
luteum in the sheep. Phil. Trans. B., vol. 196.
1904 The oestrous cycle in the common ferret. Quart. Jour. Mic.
Se., vol. 48.
1910 The physiology of reproduction. London, 1910.
MarsHatu, F. H. A., AnD Jotuty, W. A. 1905 The oestrous cycle in the dog.
Phil. Trans. B., vol. 198.
MarsHat., F. H. A., anp Runciman, J. G. 1914 On the ovarian factor con-
cerned in the recurrence of the oestrous eycle. Jour. Physiol., vol. 49.
PEARL, R., AND Surracn, F. M. 1914 On the effect of Corpus luteum substance
upon ovulation in the fowl. Jour. Biol. Chem., vol. 19.
PRENANT, A. 1898 De la valeur morphologigue du corps jaune, son action
physiologique et therapeutique possible. Rév. génér. d. Sciences pur.
et appl., vol. 9.
ReicHErRT, C. B. 1861 Beitraige zur Entwicklungsgeschichte des Meerschwein-
chens. Abh. d. Kgl. Preuss. Akad. d. Wiessensch, Berlin.
Rein, 1883 Beitrige zur Kenntnis der Reifungserscheinungen und Befruch-
tungsvorgiinge am Siugetierei. Arch. f. Mikr. Anat., vol. 22.
RupascuKin, W. 1905 Uber die Reifungs—und Befruchtungsprocesse des
Meerschweincheneies. Anat. Hefte., vol. 29.
Rugg, C. 1913 Ueber Ovulation, Corpus luteum und Menstruation. Arch. f.
Gynikol., vol. 100.
SANDES AND SKROBANSKY (Quoted from Oppenheim’s Handbuch der Biochemie
Dp ods).
Scoutz, 1829 Observationes de cobayae. Hist. Nat. Diss. Berlin (quoted from
Bischoff) .
Stockarp, C. R. 1912 An experimental study of racial degeneration in mam-
mais treated with alcohol. Arch. Internal Med., vol. 10.
1913 The effect on the offspring of intoxicating the male parent and
the transmission of the defects to subsequent generations. Am. Nat.,
vol. 47.
StockarD, C. R., AnD Papanicontaou, G. N. 1916 A further analysis of the
hereditary transmission of degeneracy and deformities by the de-
scendants of alcoholized mammals. Am. Nat., vol. 50.
THE AMERICAN JOURNAL OF ANATOMY, VOL. 22, NO. 2
PLATE 1
EXPLANATION OF FIGURES
The figures in all of the plates are photomicrographs made by Mr. Wm. Dunn
of the Photographic Department of Cornell Medical School.
1 Squamous epithelial cells contained in the vaginal fluid during the first
stage of oestrus from animal 1089 2. The vaginal fluid at this time is mucus
filled with abundant cells of this type.
2 Cells from the second stage vaginal fluid. The great majority are squa-
mous epithelial cells from the wall of the vagina with a few uterine epithelial
cells. From animal 1066 @.
3and4 Cells of the second stage more highly magnified from 1066 @ .
DIOESTROUS CYCLE IN THE GUINEA-PIG
CHARLES R. STOCKARD AND G. N. PAPANICOLAOU
PLATE 1
267
PLATE 2
EXPLANATION OF FIGURES
5 <A smear of the fluid during the third stage, from animal 1104 2. This
shows the arrival of myriads of leucocytes among the epithelial cells in the
vaginal fluid. Such an appearance is characteristic of the third stage.
6 Amore highly magnified view of the same stage showing in clearer detail
the cell structures.
268
DIOESTROUS CYCLE IN THE GUINEA-PIG
CHARLES R. STOCKARD AND G. N. PAPA NICOLAOU
Ie Ww
Pe
i x a oe K
TR he ‘ Gy me Pathe <e
v ValMOutecy +
ee : Li Ee
te Were yan
ave
Pte St ey BAS Sa a epi
oS Fhe HRY ZA a
PLATE 2
PLATE 3
EXPLANATION OF FIGURES
7 and 8 Highly magnified epithelial cells containing many leucocytes within
their cell-bodies. A condition typical of the third stage—also from 1104 @.
9 A smear showing the presence of red blood corpuscles in the vaginal fluid
during the short period of hemorrhage, following the third stage. From animal
1099 9. rc, red corpuscles.
270
DIOESTROUS CYCLE IN THE GUINEA-PIG
CHARLES R. STOCKARD AND G. N. PAPANICOLAOU
PLATE 3
—
271
PLATE 4
EXPLANATION OF FIGURES
10 A section of the resting uterus during dioestrum, four and one-half days
‘after oestrus, showing the normal cuboidal ciliated epithelium—animal 1074 9.
11, 12 and 13 Sections showing the condition of the uterine epithelium dur-
ing its active secretion of mucus and the beginning of the leucocyte migration,
from animal 1089 2 in which the oestrus was just commencing—lew, leucocytes.
Note the contrast with figure 10. A corresponding smear of the vaginal fluid
from the same animal just before it was killed is shown by figure 1.
bo
~I
to
DIOESTROUS CYCLE IN THE GUINEA-PIG
CHARLES R. STOCKARD AND G. N. PAPANICOLAOU
PLATE 4
me
oa
RY
reer’
273
PLATE 5
EXPLANATION OF FIGURES
14 A section illustrating the condition of the uterine epithelium and the
accumulation of large numbers of leucocytes below the epithelium during the
second stage of oestrus, from animal 1066 9. Corresponding smears of the va-
ginal fluid at this time are shown in figures 2, 3, and 4 from the same female.
15 and 16 Sections of the uterus during the third stage of oestrus showing the
inyasion of the epithelium by migrating leucocytes. The epithelium is partially
destroyed and greatly vacuolized, as a result of the dissolving action of the leu-
cocytes, but is still adherent to the underlying stroma which also contains
leucocytes. leu, leucocytes. Both sections are from 1104 2 and corresponding
smears of the vaginal fluid from this animal immediately before being killed are
shown in figures 5, 6, 7 and &.
17 Asection of the wall of the vagina from the same animal, 1104 9, during,
of course, the same stage. The vaginal mucosa is also invaded by leucocytes
in a manner similar to that of the uterus, several epithelial cells are seen to con-
tain leucocytes within their bodies. The epithelium here is being desquamated
or thrown off while the uterine epithelium is seen to be disintegrating before
being shed. leu, leucocytes.
PLATE 5
DIOESTROUS CYCLE IN THE GUINEA-PIG
PAPANICOLAOU
G. N.
CHARLES R. STOCKARD AND
PLAT i: 6
EXPLANATION OF FIGURES
18 <A section of the uterus from animal 1099 2 during the fourth stage, the
short period of slight hemorrhage. The beginning regeneration of new epithe-
lium from the neck of a uterine gland is shown while simultaneously the break-
ing down of the old epithelium is still taking place, and other portions of this
section show a loss of the old epithelium from the uterine wall. A smear of the
vaginal fluid from the same animal just before killing is shown in figure 9.
19 A similar section from the uterus of another animal, 860 2, during the
same stage. This shows better the falling off of the old epithelium and the
simultaneous formation of new epithelium.
DIOESTROUS CYCLE IN THE GUINEA-PIG
CHARLES R. STOCKARD AND G. N. PAPANICOLAOU
PLATE 6
PLATE 7
EXPLANATION OF FIGURES
20 A section of ovary from animal 1089 @ killed during the first stage of
oestrus. A ripe follicle is shown a few hours before congestion of the theca
begins. A smear of the vaginal fluid from the same animal is seen in figure 1
and sections of the uterus in figures 11, 12 and 13.
21. A higher magnification of the ovum and follicular wall shown in figure 20.
22. A section of the ovary from 1066 2 killed during the second stage of
oestrus. The theca folliculi surrounding the ripe follicle has become highly
congested. 6v, blood vessels.
23 Shows at a higher magnification a clearer view of the congested condition
of the follicle in figure 22, bv, blood vessels. The nucleus of the ovum is in a
resting condition. Corresponding vaginal smears from this animal 1066 9 just
before being killed are illustrated in figures 2, 3 and 4, and a section through the
uterus in figure 14. All of these figures illustrate commonly seen second stage
conditions.
/DIOESTROUS CYCLE IN THE GUINEA-PIG PLATE 7
CHARLES R. STOCKARD AND G. N. PAPANICOLAOU
PLATE 8
EXPLANATION OF FIGURES
24 A section of the ovary from 1086 2 showing a follicle shortly after rup-
ture. The congestion in the theca folliculi is evident. 6v, blood vessels. This
animal was killed at the end of the second stage or early beginning of the leuco-
cytosis, the third stage.
25 <A degenerating atretic follicle from the same ovary as figure 24, the
cells of the cumulus odphorus are degenerating while the follicle is being invaded
by leucocytes. The ovum shows the first polar body in process of division while
the nucleus of the egg is represented by a small chromatic mass near the center.
26 An early corpus luteum from animal 1104 2 killed during the third stage.
Near the corpus luteum is seen a degenerating atretic follicle invaded by leuco-
cytes. Compare smears figures 5, 6, 7 and 8, and sections of uterus figures 15
and 16, and section of vagina figure 17, all from the same animal.
27 A somewhat older corpus luteum from 1099 @ killed during the hemor-
rhage stage. The vascularization of the corpus is apparent at the periphery
and is growing toward the center. 6v, blood vessels. Compare the smear in
figure 9, and section of the uterus figure 18.
280
DIOESTROUS CYCLE IN THE GUINEA-PIG PLATE 8
CHARLES R. STOCKARD AND G. N. PAPANICOLAOU
THE AMERICAN JOURNAL OF ANATOMY, VOL. 22, No. 2
PLATE 9
EXPLANATION OF FIGURES
28 A higher magnification of another corpus luteum from the same ovary as
figure 27. The ingrowth of the peripheral vessels is more apparent, bv, blood
vessels.
29 A fully developed corpus luteum from animal 1074 @, killed four and one-
half days after oestrus. The typical glandular structure is clearly shown,
cords of cells surrounded by capillaries. cap, capillaries. A section of the wall
of the resting uterus from the same animal is given in figure 10.
282
DIOESTROUS CYCLE IN THE GUINEA-PIG
CHARLES R. STOCKARD AND G. N. PAPANICOLAOU
PLATE 9
283
A STUDY OF THE INTERCALATED DISCS OF THE
HEART OF THE BEEF
H. E. JORDAN AND J. B. BANKS
Department of Anatomy, University of Virginia
FIFTY-ONE FIGURES (FOUR PLATES)
CONTENTS
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PENS tOlooTesMeGhOUSes ace te ee ose as ce Ae ee es be str ee 288
MITE Der eral of aN gers ene Ane ofS-c ors OnE O te eee ans ai =o) o S auatckena citar nao 289
a. she WentnGWlAr IMVOCATCUIN......... 7. \.t occ Dep eee last cei 289
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rete d Li eves e010 C55 2 5.0) 021100 Ine a ee aR te oS co Re Oe 301
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I. INTRODUCTION
This investigation involves a detailed microscopic study of the
fetal and adult myocardium of the beef, including the atrio-
ventricular bundle of His, the moderator band, and the fibers of
Purkinje. The end in view is to test, in the light of additional
data, the four chief hypotheses regarding the significance of the
intercalated discs: (1) That they are intercellular cement sub-
stance (Schwigger-Seidel,! Eberth,! Zimmerman (24), et al.);
(2) that they are regions of muscle growth, that is, differentiating
sarcomeres (Heidenhain (4) ); (3) that they are of the nature of
tendons (Marceau (19) ); and (4) that they represent local modi-
fications of the myofibrils, of the nature of irreversible con-
traction phenomena following unusual functional conditions or
1 For bibliography, and discussion of the early literature, see Jordan (5).
285
286 H. E. JORDAN AND J. B. BANKS
stresses, in essence, irreversible contraction bands (Jordan and
Steele (14) ). Dietrich (3) has proposed what appears to be a
modification of Marceau’s original interpretation in terms of a
tendinous structure, namely, that the intercalated dises are con-
stant structures formed during later myocardial histogenesis to
provide for the functional codrdination of previously incoérdi-
nated myofibril-bundles in the branching trabeculae of the
musvele-plexus.
The investigation was begun with a study of the ventricular
myocardium of the adult heart. The object was to discover the
different types of dises with respect of intrinsic structure, and
their varying relations to the constituent elements of the fiber:
the telophragmata, nuclei, sarcolemma, ete. Comparative ob-
servations were made between the right and left ventricles, be-
tween the atria and ventricles, and between the papillary muscle,
the columnae carneae, and the general myocardium, in order to
determine structural and numerical variations. Study was then
directed to the atrioventricular bundle, and especially to the
area of transition between its termination as Purkinje’s fibers
and the myocardium, with the expectation of finding here some
further clue to the significance of the discs. This expectation
was to a considerable degree realized as will be described below.
The study was completed by an examination of young and
fetal hearts, in an attempt to discover the time and mode of
origin of the dises.
The least tenable of the above-mentioned hypotheses appears
to be that of Heidenhain, namely, that the intercalated dises are
developing sarcomeres. It fails by reason of the facts, chiefly,
that the discs have a definite developmental history of their
own, that they do not occur in their definitive condition during
the stages of very rapid earlier fetal growth, that the sarcomeres
of fetal myocardium do not resemble the initial dises, and that
they do not disappear after the heart has attained its maximum
physiologic development. Heidenhain’s explanation that the
persistent dises in the full-grown heart may be of the nature of
developmental vestiges, somewhat like the epiphyseal lines of
long bones, seems inapplicable. Moreover, the different types
INTERCALATED DISCS OF THE HEART OF BEEF 287
of discs can not be ranged into a consecutive series leading to a
completely differentiated sarcomere.
Marceau’s interpretation is at first consideration more plau-
sible, especially in view of the facts that the dises very generally
divide areas of different physiologic states, and that, at least in
certain arthropod muscles, e.g., leg muscle of sea-spider and scor-
pion (Jordan (10 and 12) ), the tendon fibrils apparently dif-
ferentiate from original myofibrils; but it meets with the objec-
tion that the discs do not react to specific stains for tendinous
tissue, e.g., van Gieson’s stain (and the Bielschowsky technic;
Dietrich), and that the dises frequently lie within either con-
tracted or relaxed areas.
Dietrich’s interpretation of the discs as codrdination mechan-
isms is no more than a suggestion, and no direct evidence is given
in its support.
The original interpretation of the discs as intercellular cement-
substance finds good support only in the fact that macerated
myocardium dissociates into elements bounded by dises and sar-
colemma. But these elements do not closely resemble the stel-
late and fusiform cell-areas of the original embryonic myocardial
syncytium, nor the fusiform elements of the early fetal myocar-
dium. Furthermore, the earlier fetal heart is composed of an-
astomosing, branched, cylindric trabeculae, forming a continu-
ous network, apparently without sign of typical discs. After
prolonged maceration the heart muscle fragments also along the
telophragmata. The intercalated discs are always associated
in some manner with the telophragmata, hence in fragmenting
myocardium the plane of fracture must necessarily frequently
involve a disc. When we add to these facts the probability
that the discs as modified portions of the myofibrils are lines
of relative weakness, the behavior of the macerating myo-
cardium becomes readily comprehensible.
The conduct of the dises towards silver nitrate solutions also
need not necessarily indicate an essential intercellular cement-
substance as a constituent of the discs. It may mean only that
the dises are regions of relatively greater abundance of the more
fluid portion of the interfibrillar sarcoplasm, which may precipi-
288 H. E. JORDAN AND J. B. BANKS
tate the silver nitrate. Observations are recorded below which
indicate that the precipitation of silver nitrate within the dises
is incidental to the presence of tissue-fluid in the interstices of
the fundamental bacillary elements of the discs, which fluid has
penetrated via the telophragmata from the tissue spaces between
the fibers. In myocardium treated with silver nitrate the telo-
phragmata also precipitate the salt and appear more deeply
colored. The ready passage of tissue-fluid along the telophragma
is provided for by the close union between telophragmata and
sarcolemma.
The three most widely prevalent hypotheses above discussed
meet with such serious objections when thoroughly analyzed and
strictly applied that they must be abandoned. as complete inter-
pretations of the intercalated discs. It will be the chief burden
of this new investigation to further support the hypothesis first
suggested by Jordan and Steele (14) that the dises are of the
nature of irreversible contraction bands. The suggestion had
frequently been made by various investigators that the inter-
calated dises are related in some manner to contraction phe-
nomena, but their specific interpretation as modified irreversible
contraction bands had not been previously proposed.
Il. HISTOLOGIC METHODS
The tissues were in every case fixed in the nitric-acid-alcohol
mixture of Zimmermann (24). Parallel series of sections were
prepared according to Zimmermann’s hemalum-staining method,
and with the iron-hematoxylin-van Gieson combination. Disso-
ciated tissues were also prepared for study by maceration with
potassium hydroxid, and staining on the slide with a dilute
solution of methylene blue. Ventricular tissue was treated also
with silver nitrate solutions for study of possible intercellular
cement. Beautiful and most instructive preparations were made
also by teasing hemalum-stained blocks of tissue, and mounting
the fragments in glycerin on the slide. This last technic may
be very highly recommended as a simple routine laboratory
method for class demonstration of intercalated discs. Not only
INTERCALATED DISCS OF THE HEART OF BEEF 289
the intercalated dises, but also the telophragmata, and the iso-
tropic and anisotropic substances, stand forth with almost the
same sharpness and clearness as in sections.
III. DESCRIPTIVE
a. The ventricular myocardium
There are no striking numerical or structural differences be-
tween the intercalated discs of the right and left ventricles.
Nor do appreciable differences occur between the atria and ven-
tricles, contrary to the opinion of Werner (23). As regards the
ventricular wall, the intercalated discs appear somewhat more
numerous in the papillary muscles and in the moderator band,
than in the more peripheral myocardium. Moreover, the dises
of the moderator band, and to some extent those also of the
papillary muscles and the columnae carneae, are less compli-
cated structures, that is, they are more generally of the simple
band form. The numerical difference may inhere largely in the
fact of less coarse and therefore relatively more abundant
trabeculae in the papillary musculature. The structural dif-
ferences are probably incidental to the generally different cis-
position of the branches at wider angles with respect to the
coarser trabeculae, thus producing more oblique stresses during
contraction, and to the spiral twistings of the muscle fibers dur-
ing development and growth, in the ventricular myocardium.
Neither the numerical nor the structural differences, however,
have fundamental significance. Structural differences are largely
the result of secondary modifications of originally very similar
and simple discs. We may quite securely begin the description
of the structural variations of the discs with the general propo-
sition that they are in all parts of the heart-musculature essen-
tially of the same nature, variety, and abundance. Such varia-
tions as occur in normal and pathologic hearts are incidental
respectively to normal and modified functional activity.
The simplest type of disc in the adult heart is similar to those
which first appear in the fetal heart, and resembles a peripheral
290 H. E. JORDAN AND J. B. BANKS
deeply staining band in series with the telophragmata, com-
posed of modified bacillary segments of the included portions
of the involved peripheral myofibrils (fig. 1). The modification
shows itself chiefly in an enhanced tingibility in certain stains,
e.g., hemalum. The modification is apparently, fundamentally,
chiefly chemical. Such a dise is originally bisected by a telo-
phragma. In the case of certain of the simpler discs in which
the telophragma is not discernible, they appear to shade later-
ally into a telophragma or abut upon it at the lateral mid-point
(fig. 2). That the discs are peripheral structures for the most
part can be demonstrated by changing the level of focus, when
the dise either disappears from the field or can be traced in a
lateral or spiral direction to an underlying or overlying surface. .
The same fact can be even better demonstrated in transverse
sections. In figure 7 is shown a simple disc involving only the
peripheral myofibrils of the radial lamellae in approximately a
quarter of the circumference. In figure 8 two discs appear, one
internal to the peripheral element. In both sections the dises
are at the same level as the nucleus. Figure 25 shows a scat-
tering of smaller discs throughout the fiber, probably the result
of a spiral twisting which caused an inturning of portions of
originally peripheral discs.
In figure 1 are shown two successive discs in series with the
telophragmata. Their location and general structure agrees
with that of contraction bands. The upper two discs in figure 2
show the same structure and relationships. In figure 1 both
dises cover the entire breadth (transverse) of the fiber. Dises ©
may be of much lesser breadth, indeed including only a single
fibril; but narrower discs may also in certain cases represent trans-
verse sections of broader discs, e.g., as in figure 9. Again, similar
dises of lesser width (longitudinal) occur. These represent the
original condition, both phylogenetically and ontogenetically
(Jordan and Steele (14) ), the wider discs being a modification
resulting from a traction produced by the contracting myocar-
dium. That the discs are subjected to the modifying influence of
a traction is indicated also by the frequently constricted condi-
tion of the fiber in the region where the discs are located (fig. 1).
INTERCALATED DISCS OF THE HEART OF BEEF 291
In figure 2 a terraced or step-form of disc is shown in connec-
tion with simpler discs of the character above described. That
the latter type may be bisected by the telophragma is demon-
strated by the manner of the attachment of the sarcolemma
festoons. The same point is even more clearly demonstrated in
teased preparations. The figure illustrates also another common
feature in connection with the dises, namely, the division of a
contracted from a relaxed area along the line of the discs. In
the upper relaxed region are seen the telophragmata, the Q-discs
and the J-dises; in the lower contracted region delicate con-
traction bands alternate with lighter dises. The contracted
region stains more intensely than the non-contracted region. ‘The
dises evidently frequently act as barriers to the spread of a
particular physiologic state; but occasionally the discs are
crossed by functional phases, and so may lie in either contracted
or relaxed areas.
It should be noted also that in the terraced portion of this com-
plex disc the successive steps are so arranged that the upper border
of any one is in line with the lower border of the next higher disc,
and the left hand border of any one is in line with right hand
border of the next higher disc; that is, the arrangement is such as
would result if the several steps had originally formed portions
of the same continuous band at the upper level and had been
divided into smaller sections, which were subsequently drawn |
to successively lower sarcomeric levels in a lateral progression.
Moreover, certain terraces are united by a deeper-staining mem-
brane or ‘riser; and the relation of the involved telophragmata
is such that the membranes of opposite sides join opposite sur-
faces of the dises. Such discs are common (figs. 5, 9 and 13),
and the more general condition of terraced discs with respect to
the association of the steps and the included telophragmata is like
the one here described. But several chief variations occur: (1)
The terraces may ascend again following a descent (fig. 27); (2)
all of the levels need not be placed in the regular order above
described (fig. 9); and (3) the telophragmata may be similarly
placed on both sides of the discs. Illustration figure 2 shows
further the usual location of the dises at points where the coarser
292 H. E. JORDAN AND J. B. BANKS
trabeculae branch. ‘Terraced dises arise in at least two different
ways: (1) As dislocations of original band-forms following func-
tional or developmental stresses; (2) as concomitants of a fusion
along an oblique surface of the two originally discrete portions
of the myocardial plexus. The methods of the original formation
of the several types of terraced discs will be further described
and discussed below.
Figure 3 illustrates the opposite surfaces of the same fiber.
At the upper level of focus (a) the dise appears of the usual
simple band-form, composed of modified portions of the in-
volved myofibrils, in series with the telophragmata. There is
no evidence that this disc is bounded on either side by a telo-
phragma. In passing to the opposite surface the dise appears
distorted, as if by opposed stresses, in such a manner as to form a
two-step disc. A common telophragma bounds the lower border
of the left segment and the upper border of the right segment. |
In figure 4 is shown a similarly dislocated disc, the two seg-
ments having been moved somewhat farther apart, and having
remained connected by a deeply-staining membrane, probably
portion of a telophragma.
Another complex type of disc is illustrated in figure 5. The
band elements shade into the telophragmata. The steps are in-
terconnected by membranes. The different levels of location
of the several portions are indicated by numerals. The disc as a
whole has an interrupted spiral form, and bounds a wedge-shaped
lighter-staining area at the left.
The occasional super-nuclear position of the disc is illustrated
in figures 6, 7, 8 and 31. Figure 6 shows also the close union of
the telophragmata with the sarcolemma and the nuclear wall.
Figure 9 illustrates clearly one manner of the formation of ter-
raced discs. Here two originally discrete muscular trabeculae
have fused. The ‘risers’ or connecting membranes of this com-
plex disc have resulted from the fusion of the apposed sarco-
lemmae. An irregularly terraced dise resulted in consequence,
the several segments having been contributed in part by one, in
part by the other fiber. Since the fusion was such as to produce
disaccordance of the apposed sarcomeres, the discs became ar-
INTERCALATED DISCS OF THE HEART OF BEEF 293
ranged with respect to the telophragmata so that the opposite
telophragmata joined opposite (upper and lower) borders of the
dise-sections. In anticipation of the ensuing discussion it may be
stated here that the fundamental causal factor in the formation
of this terraced dise is believed to be the unusual stresses im-
posed upon the peripheral myofibrils in the region of the area
of fusion, incidental to the functional recodrdination required
of the fibrils. The location of dises generally near the levels
where branches arise also becomes comprehensible under this
hypothesis.
The band-forms in figure 9 are located at telophragmata levels.
In the upper portion of the field one lies superjacent to a nu-
cleus. This same disc extends for some distance into the adjacent
fiber. Such disposition of the broader discs, that is, a location
across several fibers, is a common feature. It occurs extensively
even in the Limulus heart, where the discs are numerically rare
and of the simplest ‘comb’ type (fig. 41). The condition indi-
cates a local functional alteration influencing several adjacent
fibers in a transverse plane. Such discs can be plausibly inter-
preted on no hypothesis involving growth phenomena, inter-
cellular cement, or tendinous structures. They appear to sig-
nify identical modifications resulting from identical functional
phases at the same transverse level of the heart musculature.
Fusion of two adjacent trabeculae is further illustrated in
figure 10. Here two groups of narrow band-dises occur, con-
nected by the fused sarcolemmae. ‘The formation of dises is evi-
dently closely associated with the processes of fusion among
fibers. But the location of the discs with respect to the surface
of fusion is a matter of fundamental significance. The point is
well illustrated in both of the figures 9 and 10. The dises do not
he in the line of fusion but at right (or oblique) angles to it, and
in alinement with the telophragmata. It is readily conceivable
that the fusion of the fibers involved a functional recodrdination
of groups of peripheral myofibrils. This produced unusual strains
at certain levels. Such levels offer, theoretically, favorable
sites for the formation of discs by process of modification of con-
traction bands (essentially an irreversibility) according to the
hypothesis here adopted and discussed below.
294 H. E. JORDAN AND J. B. BANKS
From the standpoint of dise-formation fusions, however, are
of two sorts: (1) such as furnish the causal factor; and (2) such
as simply distort, displace, or modify in some way, discs already
present in the fibers involved in the fusion. The second sort is
illustrated semidiagrammatically in figure 11. Here two fibers
have become fused in such a manner as to produee an an har-
monic alinement of telophragmata in the apposed fibers, the result
of the superposition of a mutual spiral twisting around a common
axis of the two fibers. Such spiral twistings and fusions are
common. They have been described also in scorpion voluntary
striped muscle (Jordan (12) ) and in human heart muscle
(Heidenhain (4) ). According to Heidenhain a similar condi-
tion results from the spiral twisting of a single fiber about its
central axis (‘‘ Plasma und Zelle,” p. 616). The festooned sarco-
lemma, according to Heidenhain’s interpretation, would here
represent inturned portions of the originally peripheral mem-
brane. The same condition would result, however, if two adja-
cent fibers fused in such a manner that the crest of a festoon
of one side alternated with the trough between two successive
festoons on the apposed fiber. The latter method appears to
be more common, though the former probably also occurs. At
any rate the spiral twisting of the myocardial trabeculae during
development and growth is a characteristic of the mammalian
heart (e.g., bulbo-spiral bundle of fibers). Under these condi-
tions the definitive position and relationships of the original
dises is secondary, a modification resulting from the twisting
and fusion of the fibers.
In figure 12 is illustrated a rare type of dise. Two fibers seem
to have fused in an oblique plane, end to end. The terraced
dise is explicable on the basis of our hypothesis of strain effects
following unusual stresses, and resulting in irreversible contrac-
tion bands. The form of this particular disc may also be in
part the result of a spiral twisting of the fiber.
In figure 13 a long terraced dise separates a deeper-staining
(contracted) region sharply from a lighter-staining region. One
of the intervals here, as frequently in such discs, between suc-
cessive terraces is of the length of two sarcomeres. On raising
INTERCALATED DISCS OF THE HEART OF BEEF 2995
the level of focus from level 2 to level 1 the dises in the upper
lighter region come into view. The latter are more delicate,
stain only relatively faintly and shade into the telophragmata.
This complex of dises may be interpreted in the light of the evi-
dence derived from the simpler conditions in figures 9 and 10.
The terraced dise probably formed along the oblique surface of
fusion of two distinct trabeculae. The band-dises in this re-
gion probably formed in connection with this same fusion as
incidental strain effects.
Special note must also be taken of the alterations of the telo-
phragmata in this region. Accessory telophragmata appear to
pass obliquely between three successive primary telophragmata.
The condition is probably the result of a rearrangement of the
telophragmata and subsequent fusion following a spiral twisting
of the fibers in this region. This group of dises no doubt suf-
fered a secondary alteration incidental to the spiral twisting.
The connecting accessory membranes between the three suc-
cessive telophragmata demonstrate the telophragma-nature of
certain of the ‘risers’ of the step-dises.
The arrangement of the telophragmata in this trabecula dem-
onstrates, moreover, the possibility of a realinement of telo-
phragmata following gross morphological changes in the trabec-
ulae. It emphasizes also the imperative necessity, for a com-
plete interpretation of the intercalated dises, of dissociating the
fundamental structure, relation, and forms of the dises from their
secondary mechanical alterations following distortion in the
trabeculae.
Figure 14 shows an unusually large number of dises within a
relatively small area. The dises he at different levels as indi-
eated by the numerals. The majority shade laterally into telo-
phragmata. Such an area would seem to defy interpretation in
terms of intercellular cement, tendons, codrdination mechanisms,
or growth areas.
Before proceeding further with the description and interpreta-
tion it may be well to emphasize the following cardinal facts: (1)
The embryonic heart-musculature is a syncytium composed of
anastomosing stellate and fusiform myoblasts with continuous
296 H. E. JORDAN AND J. B. BANKS
myofibrils; the ‘cells’ elongate into fusiform elements, the con-
stituent myofibrils meanwhile increasing in number, and subse-
quently by fusion form a close-meshed network of delicate
trabeculae (fig. 15) with still more delicate branches, for the
most part originating at very acute angles; coarser trabeculae
arise by growth and further fusions, their coarser branches com-
ing off at more obtuse angles; the myocardial plexus may suffer
still further local fusions, and becomes meanwhile subjected to
the functional stresses of opposed and oblique tensions in part
the consequence of a spiral twisting of its constituent fibers and
branches. (2) Intercalated discs develop gradually during fetal
life; they are from the beginning closely associated with the telo-
phragmata, having the appearance of thickened membranes or
portions of telophragmata; at this time the only conspicuous
stripes are the telophragmata, which appear very delicate and
irregular; these apparently developed out of the spongioplasm of
the myoblasts, while the sarcolemma develops from the cell
membrane; the discs are at first granular, and only subsequently
show the typical comb structure. (8) The dises increase in
size and number coincident with the pre- and post-natal devel-
opment of the heart, the results respectively of a longitudinal
splitting of the fibrils with their intercalated discs and a new
formation of dises, and persist under modification throughout
life; once formed the dises are apparently persistent structures
subject to growth and extensive mechanical alterations. (4)
The discs are peripherally placed, always in association with telo-
phragmata, and with the sarcolemma. (5) The dises are more
commonly located in the regions where the coarser trabeculae
branch, and frequently divide areas of different physiologic
states. (6) The myofibrils pass without interruption through
the dises; the dises are essentially modified portions of the
involved myofibrils, among the structural units of which a
relatively more abundant tissue fluid occurs. (7) In the sim-
plest condition they are similar to the contraction bands both in
structure and in their relation to the myofibrils and the telo-
phragmata; in sections stained with iron-hematoxylin§ the
narrower band-forms of discs and complete contraction bands
INTERCALATED DISCS OF THE HEART OF BEEF 297
appear practically identical; if contraction bands are conceived
to be rendered incapable of reversion to the relaxed condition,
and as such to have become permanent structures modified
under unequal functional tensions incidental to the branched
and syncytial condition of heart musculature and the spiral
twisting of certain bundles of fibers during development, and the
lateral fusion of such adjacent and mutually twisted fibers dur-
ing growth, the derivation of the various definitive types of
intercalated discs becomes clear.
With the above general features of the origin, structure and
relation of the discs in mind we may now more profitably proceed
to the further description of the various types of dises. But
before doing so a critical estimate should be made of the value
of sectioned material for the study of the character of the discs.
Sections of 10 microns’ thickness include many complete fibers,
the diameter of the fibers being on the average from 10 to 15
microns. Accordingly little likelihood remains of misinterpreta-
tion on account of a peculiarity of the plane of section, or by
reason of partial views. In order to reduce the theoretical dis-
advantages of sections to a minimum, comparative studies were
made with teased material. In teased hemalum-stained frag-
ments of the ventricle, mounted in glycerin, the discs appeared
exactly as in the sections. Occasional discs may be seen in
which a bisecting telophragma is conspicuous. These band-
forms of discs are peripheral in position; a certain number have
the form of short spirals; some are located superjacent to nuclei.
By raising or lowering the level of focus an apparently short
disc can occasionally be followed as a complete band (crescent)
across the fiber, and in some cases even as a more or less com-
plete ring or spiral to the opposite surface. Step-forms also are
abundant in the teased material; they are therefore not generally
only the optical expression in sections of transverse cuts of a
series of band discs, as might have been suspected; but they
must either be due to dislocation of original band dises or they
are originally formed as terraces. ‘This material shows clearly
also the frequent phenomenon of a division on the part of a disc
of a contracted from a relaxed area.. The teased tissue is quite
THE AMERICAN JOURNAL OF ANATOMY, VOL. 22, No. 2
298 H. E. JORDAN AND J. B. BANKS
as favorable for a study of the dises and striations as are sec-
tions; it reveals clearly also the H-dises at certain stages in the
process of contraction (fig. 32).
b. The atrial myocardium
The several new types of dises to be described for the atrium
must not be thought to be characteristic of this portion of the
myocardium. Similar dises are found also in about equal pro-
fusion in the ventricles. They are considered in this order be-
cause in some respects this selected group represents a more
complex condition.
In figure 16 is illustrated : a simple and common type of disc.
In so far however as these discs are bounded on both borders by
a telophragma they represent a secondary modification of the
original dise which is in contact with only one telophragma,
which generally bisects the disc. Both of these discs moreover
separate areas of different physiologic condition. Both discs
have the width of a complete sarcomere. The one on the left
is a two-step form, and probably arose from a. dislocation
through one sarcomere of an original band disc. In terms of a
contraction band such a dise might conceivably be the result of
the fusion of adjacent halves of successive bands, or of a second-
ary modification of a single band in such a manner as to cause
it to spread to the adjacent telophragma.
Appearances like that illustrated in figure 18 strongly sueeent
that the former interpretation of dises of the width of a complete
sarcomere as the result of a fusion of adjacent halves of succes-
sive contraction bands, is, at least in some cases, the correct one.
Here, in figure 18, two discs appear within a single sarcomere,
each bounded on opposite sides by a telophragma. If the disc-
condition is conceived to spread between the two moieties, such
discs as are illustrated in figure 16 would be formed. Whatever
the fundamental modifying factor may be that operates to con-
vert the myofibrils to the dise-condition—whether of the nature
of an irreversible contraction following uncommon stresses or
not—it acts along the line of a telophragma, causing the myo-
INTERCALATED DISCS OF THE HEART OF BEEF 299
fibrils here to be altered on either one or both sides, or (perhaps
only secondarily) between successive telophragmata.
The peculiar dise illustrated in figure 17 is of the same nature
as those in figure 16. Here, however, a central segment appears
dislocated, the three segments remaining interconnected by a
deeply-staining membrane, probably the telophragma about
which the original band disc originated.
It is significant that in the common form of terraced disc, the
lateral surfaces of successive segments are in myofibril series, that
is, the several segments do not overlap. This phenomenon is
illustrated in the semidiagrammatic illustration, figure 19. The
relatively wider space between successive disc-bundles further
strongly indicates that the terraced condition arose from a dis-
location of an original band-dise at the higher level. Such in-
terpretation involves the assumption of a realinement and fusion
of the disconnected telophragmata, for which appearances illus-
trated in figure 13 give some basis of fact. Moreover, in the
less highly differentiated condition of the trabeculae in the
younger heart, when such dislocations more probably occur, the
telophragmata are relatively less rigid and less firmly attached
to sarcolemma and nuclei (fig. 15).
Figure 20 includes discs at various stages of development, pre-
sumably from contraction bands. The uppermost one shades
laterally into a telophragma; this disc is practically a contrac-
tion band, and in so far as contraction involves a segregation
of Q-substances about a telophragma the dise is in part of
anisotropic nature (Jordan, (5) ). Similarly the two discs next
below are bands, in width more like the unmodified regular con-
traction bands of the muscle (figs. 2 and 30). The diminution
in width laterally to the character of the telophragma, illus-
trated also in figures 5, 13 and 14, corresponds with the condition
of the dises as seen in transverse section (figs. 7, 8 and 25). The
succeeding three series of discs represent modifications of con-
traction bands in that they are placed to one side of their re-
spective telophragmata, perhaps irreversible halves of contrac-
tion bands. The wide, short disc to the left is again of the modi-
300 H. E. JORDAN AND J. B. BANKS
fied type, a sarcomere in width, perhaps fused adjacent halves of
successive contraction bands.
Figure 21 illustrates a rare type of disc. It is of the simple
band type, bounded on both borders by a telophragma, and shad-
ing on the right into the lateral extension of these membranes.
Viewing the sarcomeric section as a unit, the modified dise por-
tion appears contracted. Such a disc may seem to support
Heidenhain’s interpretation in terms of a differentiating sarco-
mere; but it can equally well be interpreted as the result of the
only partial relaxation of adjacent halves of successive contrac-
tion bands, the dise representing the irreversible fused product
on the left.
Figures 22 and 23 illustrate peculiar atypical forms of discs,
several sarcomeres in width. In figure 23 the central element is a
simple band-dise with which are associated outlying modified
portions of fibrils. The entire disc-area here stains more deeply
than adjacent portions of the trabecula, indicating a different
physiologic condition in the dise region. Such discs seem im-
possible of interpretation with any degree of plausibility on
a basis of growth phenomena, tendinous fibrils, or cement
substances.
The complex disc in figure 24 likewise defies interpretation in
terms of any of these hypotheses. It is one of the most compli-
cated types, and perhaps involves secondary distortions coinci-
dent with a spiral twisting and concomitant dislocations. Fig-
ure 25 possibly represents a transection of a similar fiber, in
which portions of the originally peripheral band-dises have been
transferred centrally through spiral twistings of the fiber. Simi-
lar dises are shown in figures 26 and 27, where the irregular con-
dition is associated with a secondary longitudinal splitting of the
primary trabeculae into smaller bundles. Such splitting of
trabeculae, followed by a partially independent and opposed
functional activity, may be a factor in the formation of these
types of discs. The connecting deeply-staining membrane may
be the distorted telophragma of the original disc, or perhaps an
inturned portion of the sarcolemma.
INTERCALATED DISCS OF THE HEART OF BEEF 301
c. The moderator band
The moderator band is of importance in this connection because
of the abundant areas of transition it furnishes between branches
of the atrioventricular bundle and the myocardium. The transi-
tion area includes fibers of the nature of the subendocardial
Purkinje fibers. Moreover, the myocardial meshwork here
seems of a slightly lesser degree of modification; that is, the fibers
branch more regularly, and mainly dichotomously (fig. 29), at
very acute angles, and the discs are predominantly of the simple
band-type. The step-forms generally lack the deeply-staining
connecting membranes, which indicates, in combination with
other appearances, absence of a spiral twisting of the muscle
trabeculae.
In transection the moderator band has an oval form (fig. 28).
It is enveloped by a dense areolar connective-tissue capsule. It
contains at opposite surfaces, just beneath the capsule and
within a looser areolar connective tissue, two unequal divisions
of the main right branch of the atrioventricular bundle. The
muscle tissue also is collected into two unequal bundles, sur-
rounded by a perimysial connective tissue layer. The larger
bundle contains centrally a relatively large arteriole with two
opposite large periarterial lymphatics, and a relatively small,
more peripheral venous comes.
In the muscular portion of the moderator band contracted
areas alternate quite regularly with non-contracted areas (fig.
30). The contracted areas show relatively coarse, granular,
deep-staining contraction bands which alternate with wider,
lighter-staining discs. In the relaxed intervals the telophrag-
mata, Q-dises and J-dises are conspicuous. In certain deeper-
stained fibers additional H-dises appear (fig. 32). These latter
fibers are in the early phases of contraction. The contracted
regions stain more deeply, and have a considerably greater
diameter than the relaxed intervals (fig. 30).
The muscle nuclei of the moderator band are located in fusi-
form sarcoplasmic areas. The myofibrils are arranged peripher-
ally, and they are relatively less abundant than in the ventricular
302 H. E. JORDAN AND J. B. BANKS
trabeculae. These conditions, combined with the less differ-
entiated character of the nuclei, the form of the muscular mesh,
and the prevailing form of the dises, all indicate a relatively less
highly differentiated musculature. The sarcolemma also is
more generally festooned (figs. 29, 32, 33 and 34). The telo-
phragmata are in intimate union with both the sarcolemma and |
serrations of the nuclear membrane (fig. 34). There is not the
slightest indication in any condition of an additional mem-
brane, the alleged mesophragma (Heidenhain). Since its pres-
ence can not be demonstrated in the relatively coarse muscula-
ture of the beef heart, its occurrence in cardiac muscle seems
doubtful.
The dises are generally of the narrow band-type, in close as-
sociation with telophragmata (figs. 29, 31, 32 and 33). Step-
forms occur, but connecting membranes (‘risers’) appear to be
lacking. There is some evidence of persisting amitotic divi-
sion of the nuclei in this region. The moderator band here de-
seribed is relatively slender, and the heart is that of a young,
almost full-grown, beef.
The musculature of the moderator band furnishes an excep-
tionally favorable opportunity for testing the conclusion that
dises occasionally lie superjacent to the nuclei. The difficulty
of establishing this fact in tissues where abundant branches arise
from all surfaces of a main cylindric trabecula is fully appreci-
ated. But the illustrations given in support are of examples
where no doubt can remain (figs. 6, 7, 8 and 9). The fact is, if
possible, still more certain in figure 31; here the supernuclear
group of discs has no relation to anastomoses with extraneous
branches. Identical evidence accrues also from a study of
teased preparations. Finally, the group of discs shown in figure
31 admits of no interpretation except in terms of a supernuclear
location within the ‘cell-area’ represented by this nucleus.
The possible suggestion that the dises represent an original
intercellular substance (plus apposed cell-membranes), into which
a nucleus has migrated, can have no value as an argument for
the intercellular hypothesis of intercalated discs, since, aside
from their peripheral location, they could not as true intercellular
INTERCALATED DISCS OF THE HEART OF BEEF 303
cement-substances be normally and constantly pierced by
nuclei.
The peripheral position of the dises is well illustrated also in
the type shown in figure 33, where on the upper surface the disc
is in series with the telophragmata, while on the lower surface
it is bounded along both borders by these membranes, having
here suffered a slight spiral distortion.
d. The atrioventricular connecting bundle
Before describing the transition from Purkinje fibers to the
cardiac muscle, it becomes necessary briefly to describe the
structure of the atrioventricular bundle. This has already been
done more or less completely by Tawara (22), by De Witt (2),
by Lhamon (17) and by King (15), and we shall touch only
certain details which relate themselves to our investigation of the
intercalated discs. The atrioventricular bundle is distinctly cellu-
lar in structure. This conclusion is in accord with the descrip-
tions of all of the above-named investigators except De Witt, who
regards the bundle as a syncytium. Moreover, all agree that
certain of the myofibrils of the constituent ‘cells’ have an un-
broken course through the intercellular spaces. Agreement is
complete also with respect to the descriptions of the shape of
the cells, as somewhat modified spherical or polyhedral elements
with a crenated or serrated contour. The bi- tri- or quadri-
nucleated condition of the cells has also been noted. In general
our findings agree closely with those of Tawara (22) and of King
(L5);,
In stained sections the constituent cells of the atrioventricu-
lar bundle are conspicuous (fig. 35). Their borders -appear
serrated, the myofibrils pass directly without apparent modifi-
cation through the intercellular spaces, and the majority of the
cells are binucleated (figs. 35, 36, 37, 42, 48 and 50). The sev-
eral divisions of the branches of the atrioventricular bundle are
enveloped by a dense fibroelastic capsule, between which and
the muscular columns occurs a space (figs. 43 and 45). This
had been previously noted by Tawara (22), by Curran (1), by
304 H. E. JORDAN AND J. B. BANKS
Lhamon (17) and by King (15). It may represent a lymphoid
space, but we can find no evidence of lining epithelial-cells, in
which result we are in agreement with Lhamon and with King.
The latter two investigators demonstrated the continuity of
the sheath and the enclosed ‘lymphoid space’ throughout the
entire bundle by means of injections with india-ink and Prussian
blue. Injection of silver-nitrate solution failed to reveal lining
cells. Lhamon (17) concludes that in hearts of beef, calf and
sheep the sheath does not simulate, except: perhaps very re-
motely, a mucous bursa, as claimed by Curran; and that it is
not a part of the lymphatic system of the heart.
The nuclei of the cells are-located centrally, within a finely-
granular sarcoplasmic area free of myofibrils. The two nuclei
are almost invariably in very close apposition; frequently flat-
tened along the apposed, surfaces. They arise chiefly by ami-
totic division of a single nucleus of the original cell, a process
which can be observed in fetal hearts of from two to four months.
A few nuclei were observed in the segmented spireme condition
in the two-month fetal heart, which would seem to indicate that
mitotic division also may occur in the earlier stages. In this
respect the bundle simply agrees with ordinary myocardium,
where nuclear division is originally mitotic and subsequently be-
comes exclusively amitotic. The tri- and quadri-nucleated condi-
tion of the bundle cells follows a later similar amitotic event.
The myofibrils are relatively sparse, but are more closely
ageregated peripherally. They are collected in smaller irregu-
lar bundles, which peripherally are generally arranged parallel
with the borders of the cell. The telophragmata are conspicu-
ous among the bundles; between the bundles they appear more
delicate, distorted, and frequently interrupted.
The serrations in the enveloping sarcolemma are fixation arti-
facts, due to the close union between telophragmata and sarco-
lemma and the unequal shrinkage in fixation between the myo-
fibril bundles and the sarcolemma. ‘They are the homologues
of the sarcolemma festoons of the myocardium. The serrated
condition is rendered still more conspicuous in stained prepara-
tions by reason of the fact that the stain penetrates more pro-
INTERCALATED DISCS OF THE HEART OF BEEF 305
fusely for a short distance the peripheral ends of the telophrag-
mata (figs. 36 and 37). Between adjacent cells are larger and
smaller intercellular spaces (figs. 36 and 50); through the inter-
vening ‘intercellular bridges’ pass the myofibrils. Figure 43
shows the various shapes of the cells in cross-section. That the
above interpretation of the serrations of the cell-borders is cor-
rect is further demonstrated by the appearance of the cells in
macerated preparations. Here the cells have a sharp contour
(fig. 44). The nuclei appear homogeneous, the cytoplasm finely
granular; the myofibrils are indistinctly visible and very irregu-
larly distributed.
In figure 42 is illustrated a peculiar condition where an arteri-
ole appears to lie within the cell. This definitive condition is
probably the result of a secondary adaptation of the cell to the
growing blood vessel.
The various histologic conditions above described for the
cells of the atrioventricular bundle indicate a relatively slight
differentiation, or an embryonic condition. Such interpretation
has frequently been given to the cells and their slightly modified
forms, the Purkinje fibers. But that they actually represent
embryonic forms of myocardial fibers, that is, that they are simi-
lar to the elements from which the myocardium develops has
been disputed by certain investigators, e.g., Moenckeberg? who
points to the fact that in the human embryo they are already
clearly differentiated from the myocardium at the fifth fetal
month. In the beef heart they can be readily distinguished
already at the end of the second month. But the very close
structural correspondence between the cells of the atrioventricu-
lar bundle and the myocardium in the two-month fetal heart of
the beef very strongly suggests the interpretation of the three
elements in terms essentially of a difference in degree of pro-
gressive differentiation. This point will be further discussed
below.
The presence of myofibrils and especially of telophragmata in
the cells of the atrioventricular bundle characterizes them as
2 Cited from Lange (16).
306 H. E. JORDAN AND J. B. BANKS
muscular in nature. They however lack intercalated discs; the
intercellular spaces and cement substance have no resemblance
to intercalated discs. The atrioventricular bundle is originally
and definitively cellular. The myocardium is both originally
and definitively syncytial, and the intercalated discs arise as_
secondary modifications at certain levels of the trabeculae
(transiently fusiform elements in the early fetal heart) in rela-
tion to telophragmata. The closest points of resemblance be-
tween the cells of the atrioventricular bundle and the trabeculae
of the myocardium are the presence of myofibrils, and their con-
tinuity through intercellular spaces and intercalated discs
respectively.
e. The fibers of Purkinje
We may now more profitably return to the description of the
transition area between the atrioventricular bundle and the
ventricular myocardium. Here we encounter the fibers of
Purkinje. Tawara was the first to describe the continuity of the
atrioventricular bundle with the Purkinje fibers. This obser-
vation has been repeatedly confirmed by other investigators;
vide, e.g., Retzer (21). The Purkinje fibers (cells) are essen-
tially identical with the cells of the atrioventricular bundle,
only somewhat modified by elongation, fusions into fibers, and a
higher degree of differentiation. The latter consists in a rela-
tively greater abundance of myofibrils, which are more regu-
larly disposed and less distinctly aggregated into smaller bundles,
coarser and more conspicuous telophragmata, and the presence
of simple band- and step-forms of intercalated dises (figs. 46 to
48 and 51).
The Purkinje-fiber transition-area is definitively a syncytium.
This conclusion agrees with De Witt’s (2) description of these
fibers as forming a syncytium in man, dog, cat, sheep and calf.
In the dog embryo De Witt describes the Purkinje fibers as com-
posed of ‘single short clear cells.’ The definitive. condition in
the beef heart still gives evidence of the originally cellular
structure of these Purkinje fibers (fig. 51).
INTERCALATED DISCS OF THE HEART OF BEEF 307
Figure 45 shows a transection of one of the terminal branches
of the left atrioventricular bundle where it passes under the
endocardium to unite with the ventricular myocardium. The
fibers are still enveloped by a connective tissue sheath enclosing
a subjacent lymphoid space. The nuclei lie in a finely-granular,
delicately-reticular, central, sarcoplasmic area of fusiform shape
(figs. 46 to 48). The myofibrils are peripherally arranged, in
general in delicate radial lamellae (fig. 47). Simple dises occur
sparsely, in close connection with the telophragmata (figs. 46
and 48). Some are located at nuclear levels. Deeply-staining
connecting-membranes may occur in the step-dises (fig. 48).
They probably represent the fused sarcolemmae along the line
of union of two cells which have fused in the formation of a
fiber.
Figure 46 would at first consideration seem to furnish incon-
trovertible proof of the inadequacy of the interpretation of in-
tercalated discs as intercellular cement substances, for here we
have a single elongated cell upon which appear several inter-
calated discs, at least one of which is supernuclear in position.
But conditions like that illustrated in figure 51 rob this illus-
tration of its apparent finality in this connection, since it indi-
cates that these discs may actually be related to lateral sur-
faces of fusion. This possibility, moreover, in part at least
explains the supernuclear position of intercalated discs. An
attempt will be made below to harmonize the apparent dis-
crepancies here suggested.
When we pass now again to the moderator band, we find the
same series of events. The cells of the atrioventricular bundle
(fig. 50) pass more or less abruptly into Purkinje fibers (fig. 49,
above), and the latter by more gradual stages pass into the myo-
cardial meshwork (fig. 49, below) where simple band-forms of
discs appear.
The difference in shape of the nuclei in these several regions is
also noteworthy. In the cells of the atrioventricular bundle the
nuclei are generally spherical or stoutly oval, and paired; in the
Purkinje fibers they are still substantially of the same shape,
308 H. E. JORDAN AND J. B. BANKS
but seattered; in the myocardial trabeculae they are relatively
larger and elongated elements (fig. 49).
Figure 51 illustrates conditions at the level of transition be-
tween the Purkinje fibers and the myocardium of the moderator
band. The three cells shown are histologically of the Purkinje
type, and are in process of fusion to form a fiber. Various short
dises oecur all along the surfaces of fusion. The connecting
membrane represents the fused sarcolemmae of the adjacent
fibers. The discs appear to have arisen peripherally in con-
nection with these areas of fusion. These are, however, not in the
line of fusion, but at various angles to it, and in connection with
the telophragmata. The appearance is such as to suggest a pene-
tration of intercellular fluid along some of the telophragmata
peripherally; the telophragmata may furnish more favorable
channels for the capillary imbibition of such fluids; the fluids
might conceivably alter the myofibrils in the close vicinity of
these telophragmata into the disc-structure. }
The above interpretation of the discs in terms of a local chemi-
cal modification of the myofibrils by tissue fluid, which at first
consideration seems plausible, is stated simply for purposes of
sharper contrast with the interpretation which seems to us, in
the light of more inclusive evidence, to be the correct one; namely,
that the intercalated discs, many of which undoubtedly arise in
connection with surfaces of fusion, are the products of modifica-
tions, of the nature of irreversible contraction bands on the
peripheral myofibrils, resulting from unusual strains upon the
fiber at the points of fusion incident to a rearrangement and new
coérdination of the peripheral fibrils in accord with the new
stresses imposed by the fusion of distinct cells into a unit fiber.
This point will be further discussed below.
f. The fetal myocardium
This order of description follows the actual order of the in-
vestigation. It might at first seem a more logical procedure to
have begun the description with the younger fetal material and
then to have passed from that through later fetal and early
INTERCALATED DISCS OF THE HEART OF BEEF 309
post-natal to the adult conditions. But in the actual investi-
gation it was found necessary to pass in the reverse order, for
only in this way were these earliest fetal conditions correctly
interpreted. Conditions in the Purkinje fibers of the adult
heart served as the connecting link, and the interpretative key.
Once the intercalated discs were discovered and interpreted
in the Purkinje fibers (fusing cells) and in the early fetal heart,
these simple conditions threw much light upon their definitive
structure and relationships. Fetal and adult conditions served
mutually to disclose the correct interpretation of the discs.
The youngest fetal heart studied was that of the end of the
second or the beginning of the third month. The ages specified
for the fetal hearts can only be regarded as close approximations.
The youngest heart measured 32 mm. from base to apex, and 25
mm. at its widest point. This heart takes us very close, if not
actually to, the first beginnings of the intercalated discs. At
this stage the ventricular myocardium consists of closely-com-
pacted, slender, fusiform elements (fig. 38). The resemblance
to smooth-muscle structure is striking. This resemblance has
not to our knowledge been previously pointed out. It is signifi-
cant from the point of view of comparative histogenesis that
cardiac muscle should pass through a transient phase of develop-
ment in which it resembles definitive smooth-muscle tissue.
Striped voluntary muscle of vertebrates likewise passes very early
in its histogenesis through a very similar condition. In their
earlier embryonic condition smooth muscle and cardiac muscle
both consist of stellate and irregular elements whose processes
have anastomosed to form a syncytium. The general idea that
smooth, cardiac and striped skeletal muscle represent essentially
successively higher stages of differentiation receives additional
support in the evidence that heart muscle and skeletal muscle
pass through a smooth-muscle stage.
But the cardiac muscle even at this early stage contains
simple intercalated discs. The question then ‘arises as to why
neither smooth nor skeletal muscle contain similar discs. The
answer probably inheres in the functional differences. The
rhythmic contraction of heart muscle even in early fetal conditions
310 H. E. JORDAN AND J. B. BANKS
probably underlies the formation of intercalated discs in cardiac
muscle, presumably as the effect of strains to which neither
smooth nor skeletal muscles are subjected, at least not at corre-
spondingly early stages.
The close essential resemblance between dises of adult Limulus
heart muscle (fig. 41), and of fetal mammalian heart and the
simpler types of vertebrate hearts in general, is striking and
significant. In the Limulus heart the dise is clearly a modifi-
cation of the myofibrils about a level bisected by a telophragma.
The structure of the intercalated discs in the Limulus muscle
(9 and 11), their relation to telophragmata, resemblance to con-
traction bands, and their relative scarcity, seem to permit of no
interpretation other than one in terms of a modified contraction
band. This being so in Limulus myocardium, and also in hearts
of lower vertebrates (e.g., teleost fish and amphibia; Jordan and
Steele (14) ), the conclusion seems to follow logically that a very
similar structure in the fetal mammalian heart has a similar
origin, and that its later condition must be explained in terms
of further additions and modifications.
It was formerly thought that in the mammalian heart inter-
calated dises did not appear until some time after birth. Jor-
dan and Steele first described their occurrence in the heart of
pre-natal life in the case of the guinea-pig. Here they were
described as first appearing during the last week of the gesta-
tion period. Jordan and Steele (14) had studied also earlier
fetal hearts but were unable to identify the beginnings of dises.
It may be that dises actually did not occur earlier in the guinea-
pig heait. Or it may be that on account of the relatively finer
structural features they were not discernible. But our experi-
ence with the beef heart leads us to surmise that the reason for
the failure to identify earlier the discs in the guinea-pig fetus
lay in an unsatisfactory staining.
In looking for dises in the fetal beef-heart we studied first the
four-month heart. Dises were not at first clearly identified
though there seemed to be some vague and uncertain evidence of
their presence. We then proceeded to a study of the seven-
month heart. But meanwhile we had prepared tissue also from
INTERCALATED DISCS OF THE HEART OF BEEF oll
a two-month heart for study of the origin of the cells of the
atrioventricular bundle, and the manner by which they became
binucleated. This tissue was deeply stained and at once clearly
showed intercalated discs in the fusiform cells. The resemblance
between the histologic features of the heart of the beef-fetus
at two months and those of the adult toad-heart, for example
(Jordan and Steele), is striking. Tissue from the four-month
heart was then restained, when the discs became clearly visible.
And in the seven-month heart the discs were abundant and of
substantially identical structure and relationship, except as
altered by a coarsening, and the extraneous mechanical factors
incidental to development, which factors continue to operate as
modifying influences through postnatal growth and development.
As concerns the myofibrillar elements the early fetal heart is
syncytial. But at two months, fusiform cells are plainly dis-
tinguishable. They contain an oval vesicular central nucleus.
Certain nuclei are in process of amitotic division. The myo-
fibrils are. sparse and peripherally arranged. The telophrag-
mata are delicate but conspicuous, and peripherally among the
fibrils Q-dises are faintly discernible. Delicate, deep-staining,
granular discs appear fairly abundantly peripherally, apparently
as modifications of the telophragmata (fig. 38). The cells are
beginning to fuse to form the coarser trabeculae characteristic
of later developmental conditions. It seems probable that the
roughly-dichotonous division of the trabeculae of succeeding
earlier stages, characteristic also of the moderator band (fig. 29),
results from a central fusion of such fusiform cells, the branches
representing the more widely spaced and unfused distal pointed
ends of these fusiform elements. These terminals fuse with
other similar terminals in the formation of the more regular
meshwork of the later fetal heart.
The dises appear at right angles (approximately) to the sur-
face of fusion, rarely in the surface of fusion as when two cells
fuse end to end. Where cells fuse in this manner, along oblique
surfaces, a recoérdination of the constituent myofibrils must be
effected along such surfaces, and the stresses involved may effect
the modification of the myofibrils which constitute the inter-
312 H. E. JORDAN AND J. B. BANKS
calated dises, perhaps in essence irreversible contraction bands.
Such originally modified areas may become secondarily further
modified through the influence of, or by the addition of, rela-
tively more abundant tissue fluid upon which the reactions to
silver nitrate depend. It should be emphasized that the telo-
phragmata react similarly to silver nitrate, which indicates that
the telophragmata are the more direct paths for the penetration
of the tissue fluid, which fact further explains the presence of
tissue fluid in the discs because of the intimate relationship to
telophragmata. In adult ventricular tissue tested with silver
nitrate, the latter is precipitated in the spaces between adjacent
fibers, in the telophragma, and in the discs. The close union of
the telophragma with the sarcolemma gives the mechanical ex-
planation of the penetration of tissue fluid from exterior towards
center via telophragmata.
In the two-month fetal heart we certainly come very close to the
beginning of the discs. The embryonic heart is a syncytium, ©
composed of anastomosing stellate and irregular cells.. It is only
when these have become altered into fusiform elements, and the
latter begin to fuse to form the beginning of the secondary mesh-
work of myocardial syncytium (fig. 38) that the first dises appear.
This probably occurs somewhere early in the second month, and
the actual beginning is hardly very different from the one here
described for the two-month heart.
The two-month heart shows, then, conclusively that the dises
arise in connection with cellular fusions, as modifications of the
myofibrils in lines corresponding to telophragmata, and ap-
proximately at right angles to surfaces of fusion. The evidence
is not incompatible with our general interpretation in terms of
contraction bands, more especially when the Limulus and
lower-vertebrate hearts are kept in mind, but it furnishes no
additional support to the hypothesis and it cannot be finally
denied that the myofibril modification might possibly be of the
nature of a splicing (for purposes of recodrdination) of myo-
fibrils of fusing adjacent cells. If end to end splicing of myo-
fibrils were the complete explanation of the discs, however, it is
INTERCALATED DISCS OF THE HEART OF BEEF als
very difficult to understand their originally sharp segregation
along the telophragmata.
Study of the two-month fetal heart throws further light also
on the nature of the cells of the atrioventricular bundle and of
the Purkinje fibers. In this heart the resemblance between
these elements and the fusiform cells of the myocardium is much
closer than in later fetal hearts. The element in each case is a
fusiform cell. The cell of the atrioventricular bundle is short and
very stout, the cells of the Purkinje fibers are longer and less
stout, that of the myocardium is still longer and relatively slender.
Moreover each type multiplies its nuclei by amitotic division.
The atrioventricular bundle cell more generally has only two
nuclei; and an occasional nucleus may be seen in amitotic division.
It is quite true that even at the two-month stage the atrio-
ventricular bundle can be clearly recognized. But this fact is no
proof that these cells and the Purkinje fibers are not actually
less differentiated myocardial fibers. It seems probable, in
view of the evidence from the two-month fetal heart, that origi-
nally the three types came from a similar tissue or syncytium.
The atrioventricular bundle cells differentiate only to a certain
early stage. This stage is characterized by a stout fusiform
shape, much sarcoplasm, few fibrils slightly differentiated and
peripherally arranged. The cells, moreover, frequently have
only a single large central nucleus. The nucleus occasionally
divides by mitosis, but more generally at this stage by amitosis,
to produce a binucleated cell. The cells remain distinct, but
are closely united by intercellular bridges and continuous myo-
fibrils. The Purkinje fibers progress to a somewhat later stage
characterized by an elongated fusiform shape, amitotic division
of nucleus, and a fusion to form fibers, the fusion involving the
formation of discs. The myocardium passes through very simi-_
lar earlier stages, but progresses along the same lines to a
higher degree of differentiation. From this viewpoint it is quite
correct to speak of the Purkinje fibers and the atrioventricular
bundle cells as less highly differentiated myocardial elements.
THE AMERICAN JOURNAL OF ANATOMY, VOL. 22, NO. 2
314 H. E. JORDAN AND J. B. BANKS
IV. DISCUSSION
It becomes a relatively easy matter to support, on the basis
of observational data, any one of the earlier-proposed hypoth-
eses regarding the significance of the intercalated discs if only
dises of a certain type are selected as representing the original
form, and others regarded as secondary modifications. For ex-
ample, certain regions may be found in abundance in which nu-
cleated areas of coarse trabeculae and related branches are clearly
and sharply demarked from similar areas by a fairly uniform type
of band- and terraced-discs. Such have been published almost
exclusively in support of the intercellular nature of the discs
by Palezewska (20) and by Werner (23). No interpretation is
attempted by these investigators of such dises as are illustrated
in figures 22, 23 and 24. If we combine with such evidence also
the results of macerating cardiac muscle, when areas similar to
those above-described for sections are isolated; and the further
fact that silver nitrate is precipitated by the intercalated discs,
the evidence at first seems complete that the myocardium is
compounded of distinct cells. But such interpretation must ig-
nore the facts that cardiac muscle is originally syncytial, that
dises appear only gradually during fetal (from about the second
month) and infantile life, and that the nucleated areas outlined
by the discs and sarcolemma do not correspond closely with the
original stellate myoblasts of the embryonic myocardium nor
with their later fusiform and cylindric modifications. If we add
to these countervailing facts the further facts that many dises
are of very irregular character (e.g., figs. 24 to 27) and that
they are only incomplete peripheral band-like structures (not
membranes passing from surface to surface) occasionally super-
nuclear in position, an intercellular interpretation becomes
untenable.
Dises like the one illustrated in figure 21 seem to support
Heidenhain’s opinion that they represent areas from which new
sarcomeres arise. But the great majority of the discs are very
different from such a structure, and cannot be interpreted in this
manner. Nor do such dises resemble the differentiating sar-
INTERCALATED DISCS OF THE HEART OF BEEF 315
comeres of fetal muscle. Moreover, this disc may equally
plausibly be interpreted as a partial relaxation of adjacent halves
of two successive contraction bands. But the strongest counter-
vailing evidence to any interpretation in terms of sarcomeric
differentiation are the facts above stated that trasitions between
alleged differentiating discs and definitive sarcomeres are lack-
ing, and that the discs are not abundantly present, nor at all in
definitive form, when the heart grows most actively during fetal
life, and that they do not disappear at the close of physiologic
maturity. Moreover, the discs show a progressive increase and
development from the sparse, delicate, simple types of early
fetal life to the abundant, more robust, and complex types and
modifications of the adult heart.
When one wishes to argue for the tendinous nature of the
dises, he may point to the fact of the bulging of certain con-
tracted areas which are bounded at both ends by discs. But
again such appearances are relatively rare. Moreover, the
alleged tendons (dises) do not react to specific stains for collagen
fibrils, the dises frequently lie within contracted or relaxed
areas, and the irregular varieties have no close structural re-
semblance to tendons. The dises only fortuitously bound such
contracted bulging regions.
Similarly with respect to Dietrich’s coérdination-mechanism
theory. The discs in general occupy the proximal regions of
trabecular branches, and might perhaps serve well to codrdinate
the functional activity of the included myofibrils; but no evi-
dence accrues that such is actually the case. Our evidence
indicates rather that an attempt at codrdination (or recodrdina-
tion) is the cause of disc formation; not that the dises effect the
coordination as Dietrich (3) Bebeves.
In attempting an interpretation of the intercalated discs all
the available evidence must of course be included. The correct
interpretation must be able to comprehend in logical form all
modifications of type and relationship of the discs in fetal, nor-
mal adult and pathologic hearts. We incline to believe that the
interpretation of the discs as secondary modifications of the
myofibrils at certain areas characterized by unusual functional
316 H. E. JORDAN AND J. B. BANKS
conditions, probably excessive stresses, causing an inability on
the part of contraction bands to revert to the relaxed condition,
and as such subsequently chemically and mechanically modified,
can embrace more of the actual observational data and come
nearer expressing the real significance of the discs than any
hypothesis hitherto proposed.
In support of this hypothesis numerous comparative develop-
mental and structural data must be considered. In the first
place, the grosser developmental features and alterations must
be kept in mind and brought into line. In the interpretation
of the intercalated discs not enough attention has hitherto been
given to the gross changes in the trabeculae: (1) The myocar-
dium is originally and definitely a syncytium, both with respect
to the grosser anastomoses between the trabeculae through their
branches and with respect to the myofibrils; however, towards
the end of the second fetal month, the myocardium consists of
closely compacted slender fusiform elements, resembling adult
conditions in smooth muscle, but the delicate intercellular
bridges with the continuous myofibrils meanwhile still effect a
syncytial structure. (2) The more delicate trabeculae of the
later fetal myocardium lengthen and coarsen through fusion
and intrinsic growth, and the originally more delicate branches
undergo similar changes and in many instances alter their origin
at sharp angles to origins at less acute angles. (8) In the proc-
esses of later development the ventricular fiber-bundles and
their constituent trabeculae undergo spiral twistings (e.g., the
bulbo-spiral band: Mall (18), Am. Jour. Anat., vol. 11, 1911,
fig. 19, p. 262) which involve secondary fusions of adjacent
trabeculae and distortions of branches, including in certain
cases an inturning of a portion of the originally peripheral sarco-
lemma (see also Heidenhain’s ‘‘Plasma und Zelle,” figs. 297e,
298 and 300, and diagram fig. 353, p. 616; and Jordan’s (12),
‘Studies in Striped Muscle Structure,” No. III, Anat. Rec., vol.
6; TOI).
With respect to the finer microscopic features, the following
changes must be kept in mind: (1) The discs are invariably re-
lated spatially to the telophragmata, being bounded on one or
INTERCALATED DISCS OF THE HEART OF BEEF 91 A
both sides or bisected by them, and, at least occasionally, shad-
ing laterally into these membranes. (2) The telophragmata are
in close union with the myofibrils, the sarcolemma, and the
nuclear wall. (3) The dises are peripherally placed and consist
of associated local modifications of adjacent myofibrils.
The developmental features that require emphasis in this con-
nection are: (1) The absence of discs in the embryonic myocar-
dium; the discs appear only gradually in fetal life (beginning
about the second month) as delicate peripheral bands, apparently
as thickenings of parts of the telophragmata; they increase in
number, size and variety during the period of the growth of the
heart; these developmental changes recapitulate the phylo-
genetic history of the discs, as first pointed out by Jordan and
Steele (14), who found them in hearts from teleost fishes to
birds, and even in the Limulus heart (Jordan (9 and 11) ) where
they are exclusively of the simple-comb type (sometimes in the
shape of a two-step form), located at telophragmata levels. (2)
The more complex types of discs can all be referred to the
simpler band types, as mechanical secondary modifications of
these simpler types. (8) The simplest discs consist of rows of
bacillary modified foci on adjacent fibrils.. (4) Hypertrophied
and atrophied pathologic myocardia are characterized by definite
types of dises, complex serrated forms and narrow comb forms
respectively (Dietrich (3); Jordan (6, 7 and 138) ).
The close structural similarity of the original and simplest discs
to contraction bands, and their identical location with respect to
the telophragmata, suggested an origin of discs from modified
contraction bands. A contraction band in a stained section of
certain insect muscle fibers (leg or wing; Jordan (10) ) has the
appearance of the simplest type of intercalated disc. If it be
assumed that certain bands, on account of excessive strains,
become incapable of reversion, then the possible beginnings of
discs seem to be present, which simple dises are correctly con-
ceived to be capable of modification through the operation of
mechanical factors into the various types of dises above described.
It seems desirable at this point to trace the probable steps, as
suggested in the histologic preparations, by which the more
318 H. E. JORDAN AND J. B. BANKS
complex types of discs originate from the simpler band-dises.
The first types in the order of simplicity are the terraced forms.
The same explanation that applies to a two-step form will apply
also to multiterraced forms. Moreover, the explanation must
hold as well for a terraced type in which the steps are only of one
order (descending or ascending) as also for those in which the
steps are of a double or compound order (descending combined
with ascending). But as we shall see the same explanation need
not apply also to the irregular terraced types.
Obviously one of two explanations might apply to the terraced
types of regular order: (1) They might have resulted from a dis-
location of an original band form; or (2) they might have re-
sulted from the close allocation of originally disconnected short
bands. The fact that the interval between successive steps may
be one or several sarcomeric segments need not affect this con-
clusion. In the first case specified, connecting membranes or
‘risers’ would not be expected. Such step-forms appear abun-
dantly. It should be noted also that generally in the case of
step-forms the involved myofibrils are divided into bundles
corresponding in width with the width of the step-segments
(figs. 2, 13, 19 and 26). In the second case specified, the con-
necting membranes might conceivably be either a portion of the
sarcolemma or a portion of a telophragma. ‘The possibility of
a contributory mesophragma need not be considered, since no
evidence appears that such an alleged membrane (Heidenhain
(4) ) actually occurs in the cardiac muscle of the beef. Where
a secondary spiral twisting of the fiber is superimposed, the con-
necting membrane may very likely be an inturned portion of the
sarcolemma. In the absence of a spiral twisting, in which case
the membranes (‘risers’) are relatively delicate, the connections
may be formed by portions of an involved telophragma. But
as we saw from a study of the first origin of dises in the fetal
heart, step-discs may arise in relation to oblique surfaces of
fusion, and in such instances the connecting membranes are also
portions of the fused sarcolemmae of adjacent fibers. Whether
the fasciculation of the trabeculae above mentioned in connec-
tion with terraced discs lacking connecting membranes is sec-
INTERCALATED DISCS OF THE HEART OF BEEF 319
ondary to the formation of the step-dises or a result of the dislo-
cation of an original straight band-dise is uncertain, and not of
fundamental significance.
If the terraced forms of discs were the result of a dislocation of
a simple band disc, then it might seem to be required that the
involved telophragmata should show a distortion. Such is not
generally the case. Figure 13 shows an exception. But a care-
ful consideration of the possibilities will explain the general
absence of coincident telophragmatic distortion. If it be pre-
sumed, as seems necessary under the conditions postulated for
the formation of a certain type of terraced disc, that the involved
telophragmata are broken and the segments shifted in position,
they could only shift to some place between two sucgessive telo-
phragmata or in series with them. The former may involve
fusions between portions of successive telophragmata, a phe-
nomenon indicated in figure 13; or a blending of telophragmata.
The available evidence seems to force the conclusion that many
of the regularly terraced types of discs originate by a process of
secondary dislocation of band discs, and a shifting of the result-
ing segments to successively lower levels in a lateral direction,
due apparently to successively greater tensions laterally in the
trabeculae, the result in part of the oblique tensions caused by
the anastomosing branches, and in later stages in part probably
also to the spiral twistings of certain groups of trabeculae (e.¢.,
the bulbo-spiral band).
With respect to the irregular types of terraced discs, in which
the coarser connecting membranes are invariably present, the
processes of formation involve the fusion of apposed portions of
the sarcolemmae of the adjacent trabeculae, caused to fuse by
reason of a mutual spiral twisting. Such fusions are common in
certain skelecal muscles, e.g., in the post-abdominal segments of
the scorpion (Jordan,(12) ) and in human cardiac muscle (Heiden-
hain (4) ). In cases where peripheral discs were present in the
regions of the fusions of the involved fibers these would become
arranged in irregular step-form due to their relation to the an-
harmonic telophragmata of the fused fibers. Similarly in cases
where a single fiber is spirally twisted a portion of the sarco-
320 H. E. JORDAN AND J. B. BANKS
lemma may become inturned (Heidenhain (4) ) and form a con-
necting membrane between the inturned portions of peripheral
discs. These discs are not formed as the result of fusions in
the manner of those previously described, but are simply morpho-
logical modifications of discs already present by reason of a
secondary twisting and fusion.
From the above it seems clear that all varieties of discs can be
explained in terms of a band-dise connected with a telophragma,
as secondary modifications incident to the various tractions and
tensions acting upon adjacent groups of myofibrils, or even adja-
cent single fibrils. The latter condition would result in the
more delicate serrated types, which in the case of growing or
hypertrophying fibers would involve also the telophragmata
included among the splitting fibrils (figs. 24 to 27). The pres-
ence or absence of a delicate connecting membrane between the
segments of a step-disc in the former condition might depend
upon whether the elasticity of the telophragmata was sufficient
in any given instance to withstand the strain. ot extension to
the distance of one or several sarcomeres.
We may now return again to a consideration of the initial
stage in the formation of discs. We appreciate the fact that
the weakest link in the chain of argument in support of the inter-
pretation of the original discs as modifications of contraction
bands is the explanation of their inception. But the histo-
genetic data also seem to point to such an interpretation.
When once formed in their simplest condition, all the various
types of more complex discs can be readily explained by our
hypothesis. An explanation is not equally easy on the basis of
any other hypothesis previously proposed. The facts that the
discs make their first appearance while the heart is actively
growing (about the end of the second month in the beef) and
persist thereafter in coarsened and modified forms, and that they
are at first invariably peripheral in position, have also a special
bearing in this connection. In the growth of the fiber, myo-
fibrils are being constantly added centrally by process of splitting
from the more peripheral older fibrils of the radial lamellae. The
more peripheral fibrils are first formed and are consequently the
INTERCALATED DISCS OF THE HEART OF BEEF 321
first to function; hence they support all the strains of contrac-
tion and recoérdination at the very time when rearrangement of
fibers (trabeculae), fusions and twistings are most active, and
before they are reinforced by more central fibrils. These struc-
tural peculiarities of the trabeculae explain in a measure both the
formation of the dises as possible irreversible contraction bands,
and their peripheral location. As more centrally placed myo-
fibrils develop in later cardiac histogenesis, they would be more
likely to be modified in a similar manner at the levels of the
earlier-formed more peripheral discs, and thus the discs would
tend to grow coarser in a radial direction and wider in a trans-
verse direction. But growth in radial width is probably more
largely a matter of multiplication through fission of the disc-
units of dividing myofibrils. The initial simple dises apparently
arise both in relation to surfaces of fusion and independently of
fusions. ‘The common factor in the production of these original
dises is presumably a strain effect upon localized portions of
myofibrils causing an irreversible condition of a contraction
band.
Finally, when one turns for evidence in support of this hypo-
thesis to the Purkinje fibers one finds here a combination of the
distinctive differential characteristics of the musculature of the
atrioventricular bundle and the ventricular myocardium, namely
both serrated cell-margins (in histologic preparations) and a few
simple hand-discs. In other words, the Purkinje fibers at the
level of transition from the cells of the atrioventricular bundle
are still largely distinct cells, but they are drawn out into fibers
towards the ventricular myocardium where they contain also a
few dises, and where they are undergoing fusion. The Purkinje
fibers of the adult heart are apparently at the histogenetic stage
attained by the ventricular myocardium at about the beginning
of the third fetal month. This structural condition is incompat-
ible with an interpretation of the discs as intercellular cement
substances or as tendons. An interpretation in terms of dif-
ferentiating sarcomeres is likewise inadmissible on evidence
already stated.
one H. E. JORDAN AND J. B. BANKS
The only other hypothesis that has any appearance of plausi-
bility as suggested by certain conditions of the cells of the
atrioventricular bundle, the appearance of the early fetal myo-
cardium, and by adult myocardium treated with silver nitrate—
is that at certain levels, for some unknown cause, intercellular
tissue-fluids may penetrate via the telophragmata and modify
the myofibrils in these regions. Such an interpretation has not
to our knowledge been previously proposed, but it may at least
be stated. Once formed in this manner, the discs could again
be altered by the mechanical factors incident to development
and function as above explained. But a complete interpretation
on this basis would still demand an explanation of the original
causal factor upon which the locally increased penetration of
tissue-fluid depended.
The cause of such localized (selected) relatively more per-
vious regions is obscure, unless on some basis requiring a previous
modification of the telophragmata concerned and as a concomi-
tant result of a modification of the attached portions of the in-
volved myofibrils. Such modification might again conceivably
be a result of a local unusual functional requirement, possibly
producing an excessive strain effect. The peculiar diffuse stain-
ing-reaction of the intercalated discs in general may be the
result of a relatively more profuse collection of intercellular
tissue fluid in the already modified portions of the myofibrils
represented by the discs. This is indicated more especially by
the appearance of cardiac tissue treated with silver nitrate: the
intercalated discs are not sharply outlined, but their margins
are vague and irregular, and the myofibrils appear masked by
the granular precipitate and show no resemblance to the definite
comb-dises of the hemalum-stained tissue. The relative in-
crease of tissue-fluid in the discs is more probably the result
than the fundamental cause of disc formation.
The unit of the original dise is a modified focus of a myofibril
at the level of a telophragma. By transverse linear combina-
tions of such units, and subsequent mechanical modifications
all the types of dises may be readily conceived to be derived.
Since this initial unit (a bacillary portion of the myofibrils,
INTERCALATED DISCS OF THE HEART OF BEEF 323
bisected by a telophragma) is comparable, structurally, tinc-
torially, and in respect of relation to telophragma, to a con-
tracted portion. of a myofibril (see e.g., figure 6, illustrating
contracted leg muscle of sea-spider; Jordan (12) ), an explana-
tion of intercalated discs is suggested by the microscopic evi-
dence in terms of a modified contraction band, possibly an
irreversible band.
But this conclusion must be brought into harmony with the
fact of the formation of discs in the Purkinje fibers and in the
early fetal hearts, in relation to surfaces of fusion among adja-
cent cells and trabeculae. The hypothesis that the interca-
lated discs of heart muscle are of the nature of irreversible con-
traction bands must be able to include and harmonize the evi-
dence that in the Purkinje fibers and the fusiform elements of
the fetal heart the discs arise in relation to fusion-areas between
elongating cells like those of the atrioventricular bundle. If it
cannot do this it must be abandoned. It will be observed that
the discs do not generally arise in the areas of fusion but at
right angles (approximately) to such fusion areas. Where two
fibers fuse along oblique surfaces, the peripheral myofibrils at
least, must be brought into codrdinated functional relationship.
This conceivably involves special stresses and strains at the
point or levels of recoérdination. Since at these earlier stages
when tusions are most extensively made, the myofibrils are rela-
tively less abundant while peripherally arranged and in union
with the telophragmata, and since only the most peripheral
fibrils are probably involved in the new coordination, the periph-
eral location of the discs and their spatial relationship to the
telophragmata is accounted for.
The above discussion would seem to bring into harmony with
the newer hypothesis here accepted of the significance of the
intercalated discs, two other hypotheses, namely the inter-
cellular and the codrdination-mechanism hypotheses. The in-
tercalated dises originate along original intercellular surfaces
but not generally in such surfaces; they accordingly in part
outline more or less accurately original intercellular or inter-fiber
regions. The discs may be conceived as the result of attempts
324 H. E. JORDAN AND J. B. BANKS
at codrdination of functionally incoédordinated myofibrils of
fusing trabeculae (‘cells’) which involve unusual strains, but
they do not themselves effect the codrdination; they are effects
of functional coérdination not primarily causes of such coérdi-
nation, as urged by Dietrich (8).
V. SUMMARY
1. Intercalated discs are described in sections from the atria,
ventricles, moderator band, and Purkinje fibers of the adult
heart of the beef. No striking numerical or structural differ-
ences obtain between the discs of the right and left ventricle,
nor between those of the ventricles and atria. The types of
dises include the simple band-forms, more or less complex terraced
forms, and serrated forms. These occur in frequency in the order
named, the serrated type being relatively sparse. Discs are
somewhat more abundant in the papillary muscles than in the
ventricular wall, and are more predominantly of the band-form.
A similar statement applies also to the moderator band. Con-
sidered in toto many of the ‘band-forms’ of disc are more or
less complete rings or spirals. In the Purkinje fibers the dises
are relatively less abundant than in the ventricular myocardium
proper, and they are predominantly of the band-form, with oceca-
sional short step-forms. The several technics employed in-
clude maceration, treatment with silver nitrate solutions, and
fixation by the Zimmermann. nitric-acid-aleohol mixture with
hemalum and iron-hematoxylin staining respectively. The
stained tissues were studied in sections, and in teased condition
mounted in glycerin. The investigation included further the
study of hearts of fetuses of the second, fourth and seventh
months, and of young calves’ hearts.
2. Dises are present already towards the end of the second
fetal month (ventricle) as delicate peripheral bands, apparently
as local thickenings of the telophragmata. Subsequently to the
second fetal month the discs become progressively more abun-
dant and more robust, and after birth they become altered into
more complex terraced and irregular forms.
: e
INTERCALATED DISCS OF THE HEART OF BEEF 325
3. In the adult heart the discs are still for the most part periph-
eral, as revealed both in transverse sections and in teased prepa-
rations. They never extend completely through a fiber. They
are always intimately associated with telophragmata. The
telophragmata are in close union with the sarcolemma, the
nuclear wall and the myofibrils. In ‘their simplest form, the
dises shade laterally into a telophragma, the latter apparently
bisecting the disc. In the more highly differentiated types
(mechanically modified discs) telophragmata frequently bound
one and occasionally both surfaces of the disc.
4. The unit of structure of the simple band-dise is a modified
bacillary portion of a myofibril at a telophragma level. Such
units are grouped into bands of various widths (longitudinally)
and breadths (transversely) to form the initial discs.
5. The more complex terraced, serrated and irregular types of
dise are derived from the simple band-forms through the opera-
tion of secondary extensive mechanical and possibly also chemi-
eal factors. The fundamental mechanical factors are irregular
tensions operating in opposed or oblique directions upon cer-
tain regions during the development and functional activity of
the heart. The irregular direction of the stresses are determined
by the syncytial (meshwork) character of the myocardium. The
primary results of such stresses are further modified during
development by spiral twistings of single fibers involving occa-
sionally an inturning. of portions of the sarcolemma, and by
similar mutual twistings of two adjacent fibers resulting in
lateral fusions.
6. Terraced or step-like discs result in part from a segmenta-
tion of the original band-discs and a secondary dislocation of the
resultant segments consequent to dissimilar tractions upon
successively more lateral segments; in part they arise also along
(approximately at right angles to) the oblique surfaces of fusion
of adjacent fibers (cells), presumably as strain effects (modified
irreversible? contraction bands) resulting from a reco6érdination
of the peripheral myofibrils of the fusing fibers. Terraced discs
may be formed also as secondary modifications of original band
dises by spiral twistings of single fibers or of two adjacent fibers.
326 H. E. JORDAN AND J. B. BANKS
In the first type connecting membranes (‘risers’) are generally
lacking; when present they are very delicate and probably rep-
resent portions of an involved telophragma. In the last two
types connecting membranes are more robust and stain more
deeply, and represent fused portions of the involved sarcolemmae.
The serrated types of disc result from unequal functional ten-
sions upon the units of an original band disc in a region where
the myofibrils are undergoing a longitudinal fission in the process
of growth of the fibers.
7. Evidence is presented in contravention of the previously
proposed hypotheses concerning the significance of the discs,
namely as intercellular cement-substances (Zimmerman, et al.),
as tendinous structures (Marceau), as developing sarcomeres
(Heidenhain), and as originally codrdination mechanisms for the
myofibrils (Dietrich).
8. Histologic data are presented in further support of the
hypothesis proposed by Jordan and Steele that the simplest
types of dises are local modifications of adjacent myofibrils at
the level of a telophragma (possibly of the nature of strain effects
producing a condition of irreversibility ot contraction bands),
and that the more complex types are secondary mechanical
modifications of the simpler discs. Additional evidence indi-
cates further that the dises are incidentally modified through the
infiltration of intercellular tissue fluid along the telophragmata,
which accounts tor the precipitation of silver nitrate in these
regions. A concomitant chemical modification would account
for the relatively greater ease with which the myocardium
fragments in macerating fluids in the regions of the discs.
9. The atrioventricular bundle can be distinguished from the
myocardium already at the second month. It is composed of
short, stout, fusiform or polyhedral cells containing scattered
myofibrillar elements continuous from cell to cell. The cells
commonly contain two centrally located nuclei, closely apposed,
the amitotic division products of an originally single nucleus.
The bundle terminates distally in Purkinje fibers, which connect
with the myocardium of the ventricles and of the moderator
band. The Purkinje fibers are elongated elements similar to
INTERCALATED DISCS OF THE HEART OF BEEF 327
the cells of the atrioventricular bundle. Occasional band and
short step-like discs occur on these fibers. The transition from
the cells of the atrioventricular bundle to the Purkinje ‘cells’
is characterized by an elongation and fusion of the cells to form
true fibers (trabeculae), with intercalated dises. The interca-
lated dises of the Purkinje fibers occur (arise) along the surfaces
of oblique fusion of original cells (figs. 48 and 51). Such definite
evidence of the origin of the discs in the Purkinje fibers gives the
clue to their origin, in part at least, also in the general myo-
cardium, namely in relation to surfaces of fusion of originally
distinct elements (cells; trabecuiae). This can actually be dem-
onstrated in the early fetal heart. The origin of the discs in
regions of fusion between cells, approximately at right angles to
the surtaces of fusion and in relation to telophragmata, is inter-
preted in terms of a strain effect resulting in a local modifica-
tion of adjacent myofibrillae (essentially an irreversible con-
traction band in the initial condition) and incidental to a re-
coordination of the peripheral myofibrils of the fusing cells or
trabeculae.
10. Intercalated discs occur in the fetal heart already towards
the end of the second month as deeply-staining granular modifi-
cations of certain telophragmata in their lateral extensions
among the peripheral myofibrils. The myocardial elements are
long, slender, fusiform cells in process of lateral and terminal
fusion to form the trabeculae and branches of the later syncytial
musculature. The dises are located at angles to surfaces of
fusion. The resemblance between early fetal myocardial ele-
ments and the Purkinje fibers of the adult heart is striking. The
Purkinje fibers, as also the cells of the atrioventricular bundle
of the fetal heart, are fusiform elements whose myofibrillar con-
stituents are associated with telophragmata and extend from
cell to cell via intercellular bridges. The relation of the very
similar intercalated dises of the Purkinje fibers of the adult
heart and those of the fusiform elements of the early fetal heart
to surfaces of fusion is the same in both cases.
11. The new data disclosed in this investigation, namely, the
origin of the intercalated discs in relation to surfaces of fusion of
328 H. E. JORDAN AND J. B. BANKS
previously distinct myocardial elements, need not be prejudiced
by a-forced association with the hypothesis that the discs are
essentially irreversible contraction bands. But it may again
be emphasized that the discs do not generally occur in the sur-
faces of fusion (hence not fundamentally intercellular in char-
acter) but laterally to such areas of fusion. As regards the fetal
myocardial elements and the Purkinje cells (fibers) this is in-
disputable fact. The hypothesis here supported is simply in-
terpretative of this, in common with other, facts. Nevertheless
we believe that the hypothesis can interpret more logically and
consistently than any previously proposed the microscopic data
concerning the intercalated discs. Moreover, sight must not be
lost in evaluating the hypothesis, of the strong support it re-
ceives from conditions in the Limulus heart where the simpler
discs appear, though sparsely, in a considerably coarser and
clearer form. In the Limulus heart the discs seem to admit of
no possible interpretation except in terms of modified contraction
phenomena.
VI. LITERATURE CITED
(1) Curran, E. J. 1909 A constant bursa in relation with the bundle of His;
with studies of the auricular connections of the bundle. Anat. Rec.,
vol. 3, pp. 618-640.
(2) De Wirt, Lypra M. 1909 Observations on the sinoventricular connecting
system of the mammalian heart. Anat. Rec., vol. 3, pp. 475-498.
(3) Drerricu, A. 1910 Die Elemente des Herzmuskels. Fischer, Jena, pp.
1-46.
(4) Herpennatn, M. 1911 Plasma und Zelle, Fischer, Jena.
(5) Jorpan, H. E. 1911 The structure of the heart muscle of the humming
bird, with special reference to the intercalated discs. Anat. Rec.,
vol. 5, pp. 517-529:
(6) 1912 The intercalated dises of hypertrophied heart muscle. Anat.
Rec., vol. 6, pp. 357-362.
(7) 1912 The intercalated discs of atrophied heart muscle. Proc. Soe.
Exp. Biol. and Med., vol. 10, pp. 1-3.
(8) 1914 The microscopic structure of mammalian cardiac muscle, with
special reference to so-called muscle cells. Anat. Rec., vol. 8, pp.
423-430.
(9) 1916 A comparative microscopic study of cardiac and skeletal muscle
of Limulus. Anat. Rec., vol. 10, pp. 210-213. (Proc. Am. Assoc.
Anat. 1915).
“INTERCALATED DISCS OF THE HEART OF BEEF 329
(10) 1916 The microscopic structure of the leg muscle of the sea-spider,
Anoplodactylus lentus. Anat. Rec., vol. 10, pp. 493-508.
(11) 1917 The microscopic structure of striped muscle in Limulus. Pub.
251, Carnegie Institution of Washington, pp. 273-290.
(12) 1917 Studies in striped muscle structure, III. The comparative
histology of cardiac and skeletal muscle of scorpion. Anat. Rec.,
vol. 6, pp. 1-20.
(13) Jorpan, H. E., anp Barpin, J. 1913 The relation of the intercalated
dises to the so-called segmentation and fragmentation of heart muscle.
Anat. Anz., Bd. 43, pp. 612-617.
(14) Jorpan, H. E., anp Srrerete, K. B. 1912 A comparative microscopic
study of the intercalated discs of vertebrate heart muscle. Am.
Jour. Anat., vol. 18, pp. 151-173.
(15) Kine, M. R. 1916 The sinoventricular system as demonstrated by the
injection method. Am. Jour. Anat., vol. 19, pp. 149-179.
(16) Laner, W. 1914 Die anatomischen Grundlagen fiir eine myogene Theorie
des Herzschlages. Arch. mikr. Anat., Bd. 84, pp. 215-263.
(17) Luamon, R. M. 1912 The sheath of the sinoventricular bundle. Am.
Jour. Anat., vol. 13, pp. 55-71.
(18) Maun, F. P. 1911 On the muscular architecture of the ventricles of the
human heart. Am. Jour. Anat., vol. 11, pp. 211-267.
(19) Marceau, F. 1904 Recherches sur la structure et le developpement
compare des fibres cardiaque. Ann. des. Se. Nat. Zool., vol. 19.
(20) PauczewskKa, IRENE von 1910 Ueber die Struktur des menschlichen
Herzmuskelfasern. Arch. mikr. Anat., Bd. 75, pp. 41-101.
(21) Rerzer, R. 1908 Some results of recent investigations on the mammalian
heart. Anat. Rec., vol. 2, pp. 149-155.
(22) Tawara,S. 1906 Das Reizleitungssystem des Siugetierherzens. Fischer,
Jena.
(23) Werner, Marte 1910 Besteht die Herzmuskulatur der Siugetiere aus
allseits sharf begrenzten Zellen oder nicht? Arch. mikr. Anat., Bd.
75, pp. 101-149.
(24) ZIMMERMANN, K. W. 1910 Ueber den Bau der Herzmuskulatur. Arch.
mikr. Anat., Bd. 75, p. 40.
DESCRIPTION OF PLATES
The illustrations were made with the aid of the Bausch and Lomb camera
lucida. Unless otherwise specified all figures are of tissue fixed in the alcohol-
nitric-acid mixture and stained in hemalum according to Zimmermann’s technic,
and magnified 1500 diameters. The original magnification is reduced one-third
in reproduction.
The drawings were made with water-proof India ink of various dilutions.
As such they represent quite faithfully the appearance of sections stained with
iron-hematoxylin. If shades of blue are substituted for the black and grays
in the illustrations the appearance of the hemalum-stained sections is closely
imitated.
THE AMERICAN JOURNAL OF ANATOMY, VOL. 22, No. 2
330 H. E. JORDAN AND J. B. BANKS
PLATE 1
EXPLANATION OF FIGURES
| Portion of a longitudinal section of a muscular trabecula from the myo-
eardium of the right ventricle. The trabecula is in the relaxed condition. Two
intercalated discs are shown, at the levels of successive telophragmata, having
apparently displaced these membranes. They are of the simple band form, the
constituent elements being modified rod-like portions of the included myo-
fibrils. The fiber is somewhat narrower at the point of the location of the discs,
as if stretched in this region. The discs are comparable, structurally, to con-
traction bands which have become stretched out by reason of the tension exerted
by the adjacent contractile portion of the trabecula.
2 Portion of a longitudinal section of a branching trabecula of right ven-
tricle. A terraced form of intercalated disc divides an upper relaxed from a
lower (left) contracted region. The contracted stains more deeply than the
non-contracted region. In the latter the telophragmata, Q-discs and J-discs
are conspicuous; in the contracted region only relatively narrow contraction
bands occur, alternating with lighter broader discs. At the left is shown the
sarcolemma, thrown into arcades or festoons. These span the spaces between
successive telophragmata. Where intercalated discs occur, the point of at-
tachment generally corresponds with the midportion of the disc. In the case
of the upper two elements of this step-like disc, the telophragmata at the right
also pass to the mid-line of the discs. In so far, these elements correspond to
slightly modified contraction bands. In teased preparations of stained myo-
cardium, mounted in glycerin, the telophragma can occasionally be seen actually
bisecting a dise. The lower four elements are of identical structure, and placed
at successive sarcomeric segments in such a manner that their upper limits are
on a level with the telophragmata at the right, and their lower borders corre-
spond to the level of the delicate contraction bands at the left. The second and
third element are connected by a slightly deeper-staining membrane, probably
a sarcolemma remnant. Similar complex discs appear in teased preparations,
hence not due to any peculiarity of section.
3aandb Portion of a longitudinal section of a myocardial trabecula of the
right ventricle at a higher (a) and a lower (b) level of focus. This disc is of the
simple band-type, peripherally located, apparently displacing a telophragma.
In lowering the level of focus the dise is seen to have become dislocated or dis-
torted on the opposite surface.
1 A broad two-step dise from a trabecula of the right ventricle. The steps
are connected by a ‘riser’ in the form of a deeper-staining membrane. The dise
may represent two successive bands, but is more probably a band-disc secondarily
dislocated.
5 Complex terraced disc bounding a wedge-shaped, lighter-stained, relaxed
portion of the fiber at the left. In passing from a lower to a higher level of focus
the group of discs marked 1 and 2 come successively into view. These discs are
peripherally located. Those marked (/) shade laterally into the telophragmata.
The intermediate terraced portion (2) consists of ‘steps’ connected by deeply-
staining membraneous ‘risers.’ A complete interpretation probably requires
INTERCALATED DISCS OF THE HEART OF BEEF Bp
the assumption of a fusion along the line of the terrace of originally separate
portions of the fetal syncytium. The dise portions of the ‘terraces’ appear at
angles to the oblique line of fusion, in close association with the telophragma,
as the expression of a modification of the myofibrils by reason of new stresses
imposed incidental to a functional recodrdination of myofibrils in the altered
trabeculae. The modification may be of the nature of an irreversible contrac-
tion-band, subsequently modified both mechanically and chemically, possibly
also by the accumulation of tissue fluid.
6 Portion of a longitudinal section of a fiber of the right ventricle, showing
a dise overlying the end of the nucleus. The telophragmata are attached cen-
trally to the serrated nuclear membrane and peripherally to the festooned
sarcolemma.
7 and 8 Transverse sections of ventricular trabeculae at the level of the
nucleus, showing the peripherally disposed intercalated discs. The myofibrils
are aggregated into peripheral lamellae and central more or less irregular cylin-
ders. Some of the lamellae show a peripheral longitudinal split, probably a
growth phenomenon.
9 Portion of a longitudinal section of two adjacent trabeculae from the
right ventricle. Both fibers show a single branch demarked by an intercalated
disc. In the upper portion occur four discs of the simple band type. The upper
one on the left extends from the branch across the nucleus, into the main trabe-
cula, and into the lateral portion of the adjacent fiber. This dise can best be
interpreted according to the hypothesis which relates it to a modified contrac-
tion band. In the lower portion of the field on the fiber at the left occur three
discs at successive telophragmata levels. In the center where the two fibers
have come into close apposition, involving a fusion of the sarcolemmae in such
a manner as to produce an asymmetrical arrangement of the adjacent sarcomeres,
a long step-dise appears. The ‘risers’ here consist of the fused sarcolemmae.
10 Two adjacent fibers with sarcolemmae fused medially. Several small
band-like discs appear at the upper and lower levels of the central fusion at
approximately right-angles to the line of fusion. The lower group of two discs
lies within a contracted area. At the upper and lower terminals of the central
fused area, the myofibrils have become modified to’ form simple discs, presum-
ably a consequence of the change in the direction of function of the involved
myofibrils.
11 Semidiagrammatic drawing of two adjacent fibers whose sarcolemmae
have fused in such a manner as to produce an alternation of apposed telophrag-
mata, showing the arrangement of two band-dises with relation to the common
sarcolemmae and the telophragmata. The formation of the discs in such cases
probably proceeded the spiral twisting to which the fusion of the sarcolemmae
is due.
12 Irregular type of band-disc. Two trabeculae, or branches, have appar-
ently fused end to end at an obtuse angle. The new functional requirements
on the part of the myofibrils in this region of fusion effected a modification which
resulted in this peculiar type of disc. The disc is readily interpretable in terms
of modified irreversible contraction-bands.
332 H. E. JORDAN AND J. B. BANKS
13 Complex terraced dises from right ventricle. Groups 1 and 2 come suc-
cessively into view as the focus is lowered, and are continuous around the left
margin. The lower group separates a contracted from a relaxed region; the
upper group lies in a relaxed area. The dises are peripherally placed, and form
portions of a spiral, possibly the combined result of a fusion of adjacent trabeculae
and a subsequent spiral twisting of the new fiber. A spiral twisting is indicated
also by the fusion of the telophragmata above.
14 Portion of a longitudinal section of a myocardial trabecula of the right
ventricle showing an extensive group of band-like dises. The discs are periph-
erally located and a number can be seen to be continuous across the lateral
border as the level of focus is changed, thus revealing an annular or spiral form.
The numerals indicate successive levels of focus at which the discs appear.
The great number and considerable variety of discs in such a small area would
seem to exclude interpretation in terms of intercellular cement, tendinous
structures, or growth regions.
15 Transverse and longitudinal sections of trabeculae of right ventricle of
four-month fetal heart (compare with figures 8 and 10). In the fetal heart of this
stage the trabeculae have a relatively lesser diameter; more vesicular and more
regular nuclei; fewer myofibrils, peripherally disposed; more widely-spaced, less
robust, and less regularly arranged telophragmata.
16 Two adjacent fibers from the atrium, with typical band-dises bounded
on both sides by telophragmata. The structural units are clearly modified
portions of the myofibrils.
17 Dise from atrium, composed of three portions interconnected by a
deeply-staining membrane, probably the result of an upward dislocation of a
central portion of the original band disc.
18 Two apposed dises within the same sarcomere. They apparently repre-
sent apposed halves of successive contraction-bands, which failed to relax.
19 Semidiagrammatice sketch illustrating the possible origin of the type
of terraced disc lacking coarser ‘risers,’ from an original band-dise by process
of division and dislocation of the resulting segments to successively lower levels
in a lateral direction; and a subsequent rearrangement of the telophragmata at
regular intervals.
20. Group of discs from atrial trabecula. The discs represent various
degrees and combinations of myofibril modification.
21 Atrial disc bifureating on the right to pass into the two successive telo-
phragmata. This is the only type of disc which gives plausible basis for inter-
pretation as a region from which a sarcomere develops (Heidenhain), but it may
equally well be interpreted as a partial failure of reversion of apposed halves of
two successive contraction bands.
INTERCALATED DISCS OF THE HEART OF BEEF
H. B. JORDAN AND J. B. BANKS
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EXPLANATION OF FIGURES
22 A group of atrial discs, comprising modified portion of myofibrils of the
extent of one and two sarcomeres.
23 Atrial dise of fundamental straight-band form, associated with which
are other complete and partial sarcomeric modifications of myofibrils. The
dise-area here stains more deeply.
24 Very complicated atrial dise of the distorted serrated type, certain
portions of which are interconnected by light-staining membranes, perhaps
telophragmata.
25 ‘Transverse section of an atrial trabecula with larger peripheral disc
(above) and seattered sub-central smaller dise elements.
26 Portion of a longitudinal section of a secondarily dividing fiber from left
ventricle. The telophragmata in the several branches are at different levels.
27 Irregular type of dise from left ventricle apparently produced by a
splitting of an originally coarse trabecula into subdivisions, with dislocation of
the discs due to unequal tensions during contraction in the resulting smaller
fibers. The lightly-staining connecting membranes are perhaps remnants of
distorted telophragmata.
28 Semidiagrammatic drawing of a transverse section of a slender moderator
band, showing peripherally on opposite surfaces two branches of the right limb
of the atrioventricular bundle (A.V.B.). The muscular tissue is grouped into
two large bundles (/), the larger bundle containing a large central arteriole
(A), and a small peripheral venule (V). XX 13 diameters.
29 Portion of moderator-band musculature in longitudinal section, showing
the simpler branched condition, and the abundant band-type of dises. X 535.
30 Portion of a longitudinal section of a trabecula from the moderator band
showing a central relaxed area, and terminal contracted areas. The contracted
areas stain more deeply and show only the contraction bands and alternating
lighter-staining discs. The contracted areas have a considerably greater diame-
ter than the relaxed portion. Iron-hematoxylin and van Gieson’s stains.
31 Group of simple dises of fiber from moderator band, overlying a nucleus—
where neither tendons not intercellular cement could be expected to occur.
32 Portion of a longitudinal section of a fiber from the moderator band,
stained in iron-hematoxylin, showing the festooned sarcolemma, an intercalated
dise at the level of a displaced telophragma, the Q-, J- and /-dises.
33 A band-form of dise from the moderator band extending completely
around the periphery of the fiber, but passing in opposite directions on the
opposite surface, thus assuming a short spiral form. Probably similar to disc,
figure 3, a and b.
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INTERCALATED DISCS OF THE HEART OF BEEF
H. E. JORDAN AND J. B. BANKS
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HXPLANATION OF FIGURES
34 Portion of a longitudinal section of a trabecula from the moderator band,
showing the union of the telophragmata to the nuclear wall and to the festooned
sarcolemma. No indication appears of an additional mesophragma. Iron-
hematoxylin and van Gieson’s stains.
35 Longitudinal section of a portion of the cellular network from the right
limb of the atrioventricular bundle. The majority of the cells contain two
nuclei very closely associated. Occasional cells contain three or four nuclei.
The cells are polyhedral in shape, variously modified (figs. 37, 42, 43 and 44).
The margins appear serrated in sections (in macerated preparations the cell
membrane has a sharp contour; fig. 44). The serration in histologic prepara-
tions is an artifact due to the non-uniform shrinkage between the myofibrils
and the sarcolemma, to both of which the telophragmata are attached. The
sarcolemma stains more deeply, as do also the lateral attached portions of the
telophragmata. X 108.
36 More highly magnified portion (x) from figure 35. The intracellular myo-
fibrils are seen to be aggregated into smaller groups, more abundant peripherally.
The peripheral groups follow in general the cell contour; hence the myofibril-
groups are irregularly disposed with respect to each other, and the telophragmata
are distorted and apparently in places interrupted. Numerous intercellular
spaces occur. Certain fibrils of the myofibril-bundles are continuous from cell
to cell, forming thus a syncytium in spite of distinct cell-walls. The sarco-
lemma and the attached portions of the telophragmata stain more deeply than
the central fibrils. X 666.
37 More highly magnified cell, of modified polyhedral form, from the portion
of the atrioventricular bundle shown in figure 35.
38 Small area of ventricular myocardium of fetal heart towards end of sec-
ond month, showing several adjacent muscle cells in longitudinal section. The
cells are long, slender, fusiform elements resembling definitive smooth-muscle
cells. The myofibrils are apparently continuous from cell to cell. They are
relatively meagre in amount and peripherally arranged. The telophragmata
are conspicuous but very delicate. Peripherally, among the fibrils, Q-dises
are also barely discernible midway between successive telophragmata. Simple,
delicate, deep-staining, granular intercalated discs also occur peripherally at
telophragma levels, apparently as modifications of this membrane. The dises
do not occur in the areas of fusion between adjacent cells, but at right angles to
such surfaces. XX 1000.
39 Portion of longitudinal section of ventricular myocardium of fetal heart
of fourth month; showing the process of fusion of the slender fusiform cells to
form trabeculae, and a few simple band-like dises.
40 Portion of longitudinal section of ventricular myocardium of fetal heart
of seventh month, showing numerous band-like discs.
41 Portion of a longitudinal section of a coarser trabecula from an adult
Limulus-heart, including two intercalated dises, apparently forming a two-step
type, Separating an upper contracted from a lower uncontracted region. The
dises are at telophragma levels and apparently represent modified contraction
bands. The illustration shows clearly the close resemblance between the discs
of the adult Limulus heart and the simplest type of dise of mammalian hearts.
(Continued on page 338)
396
INTERCALATED DISCS OF THE HEART OF BEEF
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42 Transverse section of a central cell from a large strand of the right limb
of the atrioventricular bundle, containing an arteriole. This condition was
probably attained by an adaptation of the cell about a closely apposed blood
vessel.
43 Transverse section of a smaller strand of the right limb of the atrioven-
tricular bundle. This shows the variable shape of the cells, and the enveloping
connective tissue capsule. Between the sarcolemma and the capsule a space
invariably occurs, perhaps of the nature of a lymphatic channel, but not lined
by endothelial cells. The serrated borders and the perinuclear clear spaces are
fixation artifacts.
PLATE 4
EXPLANATION OF FIGURES
44 (a, b, c, d, e) Various forms of cells from a macerated preparation of the
right branch of the atrioventricular bundle. The cells vary considerably in
form and size, but can all be referred to a fundamental spherical or polyhedral
form. In unstained preparations the paired nuclei are somewhat darker than the
cytoplasm, and are homogeneous in appearance. ‘The cytoplasm appears granu-
lar, and denser peripherally. The myofibrils are barely discernible. They
occur in all portions of the cytoplasm, though more abundantly peripherally,
are very irregularly disposed, and are continuous from cell to cell. X 535.
45 Transverse section of smaller terminal subdivision of the left limb of the
atrioventricular bundle (Purkinje fibers) showing the pericellular lymphoid
spaces and the connective-tissue capsular-stroma.
46 Cell from area of transition of left limb of the atrioventricular bundle
to the Purkinje fibers. The cell, still enveloped by a capsule, has elongated
into a fiber of Purkinje. The cell is apparently in a contracted condition. Cen-
trally it contains a large sarcoplasmic area free of myofibrils. The cell con-
tains a few intercalated discs at the levels of displaced telophragmata.
47 ‘Transverse section of two adjacent Purkinje fibers. The myofibrils are
arranged in the form of delicate radial lamellae. The cells are enveloped by a
connective tissue membrane.
48 Longitudinal section of transition area from atrioventricular bundle to
Purkinje fibers. The Purkinje fiber (cell) is surrounded by a lymphoid space and
contains a step-form of intercalated disc. It probably represents a fusion
product of two originally distinct cells.
49 Transition area between atrioventricular bundle and myocardium of
moderator band. The upper portion of the illustration shows Purkinje cells,
the lower, myocardium with band-dises. In figure 50 are shown the cells of the
atrioventrieular bundle which ends in the Purkinje fibers here shown. 535.
50 Group of cells from the atrioventricular bundle of the moderator band.
Intercellular bridges are conspicuous; these are composed of myofibrils passing
irregularly between adjacent cells. > 535.
51 Portion of longitudinal section of muscle of moderator band, correspond-
ing to the Purkinje fibers of the myocardium. Intercalated dises are forming
in relation to the fused sarcolemmae of these three adjacent fibers. The form-
ing Purkinje fiber is here represented by three originally distinct cells. The
discs do not generally arise in the line of fusion but at angles to the fusion-area.
338
INTERCALATED DISCS OF THE HEART OF BEEF
H. E, JORDAN AND J. B. BANKS
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AUTHOR’S ABSTRACT OF THIS PAPER ISSUED
BY THE BIBLIOGRAPHIC SERVICE OCTOBER 27.
THE EARLY HISTORY OF THE GERM CELLS IN THE
ARMADILLO, TATUSIA NOVEMCINCTA
AIMEE 8. VANNEMAN
Contribution from the Zoological Laboratory of the University of Texas, No. 137
THREE PLATES AND TWO TEXT FIGURES
CONTENTS
rina duetrone:s: ees terrs.: Cyr eee oes os oo ks ay ee eee eee 341
PSTN ETS ADIN COTE gD ECCS 5), Ne ee ee ee 346
Gera Gels TM Cally SLAP OS. t..e cole es cys oes oa «eee eA ree 347
Maprationvrol mermvcell secs seca tert. ook e. . ws a ee e eek 350
WISCURSTOM: isa s. nuts hee Wy ed ose so ee ook eee eae et 354
ReMiIMAny, ANG (CONCIMSTONS: soem oo. |. soe 2 od ao eee eee 356
1 BHO} UKCTEA SY 0) hy alee eRe Sto Si ar ce Be SS ple Oe 357
INTRODUCTION
In addition to the interest attached to a problem of this sort,
there are three reasons for undertaking the work of the present
paper. First of all, the germ cells of the armadillo are remark-
ably conspicuous, even in young stages. Probably no other
mammal so far studied for the point in question, offers such pos-
sibilities for the solution of a yet unsettled problem. The germ
cells of the armadillo, besides being clear-cut are easily trace-
able through the tissues, without the characteristic details found
necessary for recognition in forms investigated by other workers.
Again, the armadillo presents a problem of unusual interest in
being a polyembryonic form. Here, it is a question as to whether
or not the germ cells of the embryos of a given blastocyst have
a common origin. It is to be noted that no one has ever traced
germ cells with certainty to a pre-embryonic stage in a poly-
embryonic form. The discovery by Swift (14, 715), that germ
cells in the chick migrate by way of the blood-vascular system,
stimulates further investigation as to the path of migration of
341
THE AMERICAN JOURNAL OF ANATOMY, VOL. 22, NO. 3
NOVEMBER, 1917
342 AIMEE S. VANNEMAN
germ cells in mammals. The question arises whether the germ
cells have been overlooked in the blood vessels, or whether
they never occur in the vascular system of mammals. It is
because of the before-mentioned distinctness of the germ cells
that the armadillo has been chosen and found peculiarly favorable
for this study. The species here used is Tatusia novemcincta.
Although in recent years a large amount of work has been done
on the origin and history of the germ cells in various forms, yet
in vertebrates, relatively little has been accomplished along
this line. The question in this case is a far more difficult one,
as is acknowledged by all investigators who have attacked the
problem. The possibility of distinguishing germ cells from so-
matic cells in most vertebrates is rendered smaller by the absence
of characteristic yolk substances and further, by the appearance
only in advanced stages of the various so-called Keimbahn
determinants, which serve so admirably for the definite recog-
nition of the germ cells of certain invertebrates. Modern
advances in cytological methods, however, give promise of a solu-
tion to the problem, as is evidenced by the recent results of
Rubasehkin (10), Tschaschin (10), Swift (14) and others.
It is unnecessary here to discuss the earlier literature of germ
cell history except to note that Eigenmann (’97) was the first
to give a detailed account of the wandering of germ cells in
vertebrates. He reached the conclusion that the sex cells in
fish are probably set aside as far back as the thirty-two cell
stage. This is the furtherest that any vertebrate germ cell
has been traced.
Among those advocating the early origin of germ cells, may be
mentioned Beard (’00) in his work on Raja bates. He claims that
the germ cells may be found in a stage preceding the appearance
of any real embryo, the size of the cells suggesting origin after
about the thirteenth division. These, he finds, journey from
outside the embryonic region between the blastodermic layers
upwards through the yolk sac into the splanchnopleure and gut
regions.
In 1902, Woods studying Acanthas, found that the germ cells
appear in the entoderm before the differentiation of mesoderm
GERM CELLS IN TATUSIA NOVEMCINCTA 343
and also in the yolk at the meeting point of the germ layers.
Thence they migrate to the splanchnopleure and into the epi-
thelium around the intestine, from which point they find their
way to the germinal anlage.
Allen (’06) discovered in Chrysenis that the germ cells arise
in the entoblast in the region between the area opaca and the
area pellucida, posterior and lateral to the embryo and wholly
without the zone of gastrulation. These migrate between the
entoderm cells to the mesentery and finally to the peritoneum
on either side of the latter.
Rubaschkin (’07, ’09, 710, ’12) investigated conditions in te
chick, cat, rabbit, and guinea-pig again tracing back germ cells
to the entoderm with further migration through the mesentery
to the sex anlage.
Among those working on mammals may be mentioned Fuss
(12) who studied the rabbit, pigand man. He concludes that the
germ cells first become apparent in the region of the primitive
streak where no segmentation has yet taken place in the embryo.
Scattered cells also may be seen out on the yolk, whence they
migrate to the intestinal endoderm and mesoderm en route to
the genital region.
Especially interesting are the conclusions Scnahad by Swift
(14) in his work on the chick. He finds that the germ cells
arise anterior and antero-lateral to the embryo in a specialized
region of the germ wall entoderm at the margin of the area
pellucida. They first appear during the primitive streak stage
and continue to arise up until the three somite stage. Although
first found between the entoderm and ectoderm, they later enter
the mesoderm and the forming blood vessels of the mesoderm.
By the blood, they are carried to all parts of the embryo, re-
maining distributed till about the twenty somite stage. At
this time, the germ cells begin to concentrate in the vessels of
the splanchnic mesoderm. After the twenty-five somite stage
they appear to have left the blood having passed out through
the vessel walls into the splanchnic mesoderm near the mesen-
. tery. In the thirty and thirty-three somite stages, the germ
cells are seen in the root of the mesentery and in the coelomic
344 AIMEE S. VANNEMAN
epithelium, soon migrating thence into the sex anlage. It will
be found interesting to use Swift’s work on the chick as a basis
of comparison for the present paper on the Armadillo. For this
reason, Swift’s conclusions are cited more or less in detail.
Many other investigations might be cited in this connection, but -
space and time do not permit of further enumeration.
For the material of this investigation, I am indebted to Dr.
J. T. Patterson, who has generously furnished me with an
almost complete series. The embryos for the most part were
fixed in Bouin’s fluid, and the sections stained in part in iron
haematoxylin, in part with Delafield’s haematoxylin. In the
latter, the germ cells show up exceptionally well, as Delafield’s
in coloring somatic cells relatively densely, permits the large,
clear germ cells to be easily distinguishable in their surroundings.
As most of the slides used for this work, had previously been pre-
pared for a purpose other than that of germ cell study, obviously
no selective technique could be employed for the present purpose.
However, unlike the experience of other investigators who have
studied the subject, I have found that whatever the stain or
fixing fluid used, the germ cells have been perfectly clear in the
tissues. The sections were cut from seven to ten micra thick.
It is to be regretted that the earlier stages were not cut thinner
as the germ cells of the earlier stages of development are not
grouped, but are few in number and often widely scattered and
for this reason, more difficult of detection and demonstration in
thick sections.
The following are the stages examined for germ cells: (1) early
ectodermic vesicle stages, (2) early and late primary bud stages,
(3) secondary bud stages, (4) early and late primitive streak
stages, (5) three somite stage, (6) seven somite stage, (7) ten
somite stage, (8) fourteen somite stage, (9) 4+mm. embryo,
(10) 6-mm. embryo and (11) the 10-mm. embryo. Beyond the
10 mm. embryo, the germ cells are well established in the in-
different gonad, preparatory to undergoing further development.
The series is unusually complete, there being but one stage lack-
ing which would, if obtainable, be of value in tracing the germ
cells. This gap occurs between the 4- and 6-mm. embryo stages,
but is such that it can easily be bridged over.
GERM CELLS IN TATUSIA NOVEMCINCTA 345
It will be recalled that in his paper on ‘‘Polyembryonic de-
velopment in Tatusia novemcincta,’”’ Patterson (713) has given
a thorough treatment of the early development of the armadillo.
For those, however, who are not sufficiently familiar with the
facts to follow the migration of cells, a brief resume may be
profitable. After the usual cleavage stages and the formation
of a typical mammalian blastocyst, consisting of one tropho-
blastic layer and an inner cell mass of embryonic cells, a process
of differentiation sets in through the migration of entodermal
mother cells from among the ectodermal cells. These cells,
directly or after division migrating to the under surface of the
cell mass, presently become transformed into a continuous layer
which splits from the ectoderm. Following this, the embryonic
ectoderm rounds up into a spherical mass which withdraws from
the trophoblast, and pushes into the vesicle cavity, becoming
included in a layer of entoderm. Through a process of vacuoliza-
tion, the ectoderm sphere now becomes a vesicle. It is after this
stage that the primary buds first appear from thickened areas
which have arisen on opposite sides of the eetodermic vesicle
through a shifting of cells. The primary buds show no signs of
embryonic primordia, but each directly gives rise to two second-
ary diverticula, thus forming four buds which soon extend and
begin to show the beginnings of four primitive streaks destined
to give rise to the quadruplets. Each embryo derives its ecto-
derm from a portion of the lateral plate, while the entoderm arises
in loco from the primitive entodermal sac. This description
though incomplete is sufficient to present the main points of in-
terest, and to show that a common point of origin for germ cells
of the 4-embryos of a blastocyst might, under the conditions,
be considered probable.
STRUCTURE OF GERM CELLS
Before proceeding to the history of the germ cells in the Arma-
dillo, a description of the form and structure of the cells under
consideration might be of value. On the whole, the form of the
germ cells is almost constant from the earliest stages up till the
time of the indifferent gonad. The size is equally constant—at
346 AIMEE S. VANNEMAN
least within certain limits. The primordial germ cell is large,
being almost twice the size of an ordinary erythrocyte, and in
contrast to the surrounding tissue cells, it takes a lighter stain.
It varies in shape according to its location, but is typically
spherical. At times the shape is very suggestive of amoeboid
movement. Especially is this true in certain early stages to be
referred to later. The cell outline is always definite. This is
one of the surest criteria for the identification of germ cells. The
cytoplasm is very pale and seems to be concentrated more or less
closely around the nucleus, while the space directly within the
cell membrane is practically clear. The nucleus too, is large in
comparison to the nuclei of neighboring cells, and almost without
exception is spherical in form. It may be noted that very fre-
quently the nucleus is eccentrically placed. It is usually coarsely
granular in appearance and always contains one definite dark
staining nucleolus, frequently two, and sometimes more in
younger stages. As the material used for this work was not
fixed or stained for mitochondria, these bodies were not observed.
Indeed, there appeared to be little need of using such criteria for
the detection of germ cells, since the latter are distinct beyond
suspicion without the aid of details. This statement may pos-
sibly have to be modified in regard to very early stages. The
question will receive discussion later in the paper. Concerning
other criteria used by the various investigators for distinguishing
germ cells, there is little to be said. Of course, yolk substance
is not present in this case. Neither is the ‘attraction-sphere’ of
Swift apparent, although the proper fixation and staining might
reveal such inclusions.
GERM CELLS IN EARLY STAGES
Specimen 256 is the earliest stage in which I have been able
to detect germ cells. It represents a condition where the lateral
plates, which are to be the beginnings of primary buds, are just
becoming differentiated through a shifting of cells of the young
ectodermic vesicle. The plates are merely in the process of
forming. At this time the germ cells are extremely few in num-
ber. Indeed, not more than two could be found. They are
GERM CELLS IN TATUSIA NOVEMCINCTA 347
situated between the ectodermic and entodermic layers of the
blastocyst at points where the layers are fairly widely separated
(fig. 1 and la). It is decidedly more difficult to locate germ
cells at this time than in later stages, since the neighboring
cells are naturally larger now than they are later.
Next in order is the primary bud stage represented in speci-
men 247 (fig. 2a). Here the germ cells are similarly located.
Text figure 1 represents a reconstruction of no. 247, point X
indicating the location of the germ cells observed in this stage.
Text fig. A A reconstruction of 247, point x indicating the location of the
germ cells at this stage. (This figure is taken from Patterson, 713.) It will
be noted that the germ cells are not found in this specimen in the primary bud
regions.
It will be noted that they appear outside of the points where the
primary buds are forming. No germ cells were found in the
vicinity of the primary buds. There is not a sufficient number
of primary bud stages in my possession to permit of stating defi-
nitely the location of these cells on the blastocyst at this time,
but I am inclined to believe that they probably lie gcattered
very sparsely here and there in the entoderm, chiefly, it would
seem, in the regions which do not give rise to the primary buds.
What signifiance this fact may have, it is hard to explain. I
question whether these few stray cells, found in stages before
the embryos appear, play much part in the subsequent history.
To definitely settle the matter of location, careful examinations
of a number of primary bud stages is indispensable. In figure
348 AIMEE 8S. VANNEMAN
2, two germ cells are portrayed, one in the process of division.
They will be seen to be connected by a frail strand of tissue to
the entodermal layer. A further examination of the series of
sections reveals the fact that some of the entodermal cells are
cytologically very much like the germ cells. <A study of young
stages suggests that germ cells undergo a considerable number
of divisions up until the period when they are seen to enter the
gut entoderm. After this and until they reach the gonad, they
remain in a resting stage, evidenced by the fact that dividing
cells rarely, if ever, are seen in advanced stages of development.
There is a tendency, however, for the student of germ cells to
overlook dividing cells and consider them ineligible to the cate-
gory of germ cells, just because of the fact that they are divid-
ing. This, I believe, is an explanation of the frequent low
count of germ cells in earlier stages. That it is not the only
explanation in the case of the Armadillo, however, will be shown
later. Certainly no small number of divisions must occur in
early stages, for the comparison in numbers of germ cells in
early and late stages is striking. The small number of germ
cells found in no. 247 may be explained partly by the fact that
the series was cut 10 micra thick, thus obscuring some cells
which in thinner sections might have been visible. Such a
thickness in older stages is not so disadvantageous, because of
the greater number of germ cells, permitting of Just so many
miore chances of cutting through a cell instead of just missing it.
The stage just preceding that described for no. 256 was care-
fully scrutinized for germ cells, but results were fruitless. It
might be remarked that the next stage younger in my posses-
sion is an early ectodermic vesicle before the shifting of any
cells preparatory to lateral plate formation—a stage consider-
ably younger in time, even if not in appearance, than no. 256.
As a matter of fact it is known that the primary buds do not
start to differentiate for a considerable time after the com-
pletion of the ectodermic vesicle (Patterson, 713). Unusual
interest attaches itself to the study of such an ectodermic vesicle,
because of the before-mentioned possibility of discovering some
common place of origin in the vesicle wail for the germ cells of
GERM CELLS IN TATUSIA NOVEMCINCTA 349
the four embryos which are to develop in the diverticula of this
same vesicle. The failure to find germ cells at this time may be
due to one or more of several causes. It is possible but not
probable, that germ cells at this early period, even though
present, have not yet assumed the form which in future stages
become so constant and reliable for identification. Moreover,
the somatic cells at this time are lacger than later, having
undergone fewer divisions—thus making it less easy to distin-
guish, by size relationship, the germ cells from surrounding
cells. Again, it may be questioned whether the germ cells arise
at all before the appearance of the primary embryonic rudi-
ments—such a suggestion excluding the possibility of a common
origin for germ cells in a polyembryonic form. It will be remem-
bered that Swift (14) in his study of the chick arrives at the
conclusion that the germ cells arise at the time of the primitive
streak in a specialized region of the germ wall. That is, he
believes that certain entodermal cells of the germ wall at this
time are producing, through division, germ cells which cytologi-
cally are similar to, the cells of the germ wall. Thus, according
to Swift, eaclier than the primitive streak stage, germ cells, as
such, are not to be found. Whether or not this fact, unmodified,
holds true for the armadillo, notwithstanding that a few germ
cells may be seen before embryonic primordia appear, is a
question. It is the desire of the writer to demonstrate that in
all probability not only the time, but the mode of origin of
germ cells in the armadillo is similar in most respects to that
described: by Swift foc the chick.
MIGRATION OF GERM CELLS
Although the germ cells in the stages Just described may be
in the act of migrating, it seems best to discuss them merely as
in the condition found in early stages, and to describe the mi-
gration as beginning with the secondary bud stage, from which
time the wandering may more surely be followed. In speci-
men 290, representing an early secondary bud stage (fig. 3a),
the germ cells have become more numerous and are located on
the entoderm a little lateral to the primitive streak region which
350 AIMEE S. VANNEMAN
is beginning to give off a few mesoderm cells. These cells are
found in the neighborhood of each of the four embryonic areas,
and must either have migrated to these points along the blasto-
cyst entoderm, or else they are arising de novo from the yolk
sac entoderm at the point of contact of the latter with the em-
bryonic area. A further discussion of this point follows in the
conclusions. In any case, some of the cells are slightly amoe-
boid in shape and become more so in late secondary bud stages
when they appear to be traveling toward the ventral and cen-
tral portions of the future embryo in the posterior primitive
streak region (figs. 4 and 4a). In no. 290, some of the germ
cells lie in the space between the entoderm and the ectoderm
in a region between the embryonic areas as shown in text figure
2, a detail figure of the same being found in figure 3. Other
germ cells are to be seen in the embryonic areas. These lie close
upon the entoderm seemingly in the act of pushing their way
into the layer destined to become the gut entoderm (fig. 4).
A considerable number of divisions seem to occur among the germ
cells just prior to their entrance into the gut entoderm. In late
secondary bud stages where the diverticula are undergoing a
process of further: elongation, conditions are similar to those
just described. Frequently, germ cells are found among meso-
derm cells which have budded out a distance from the primi-
tive streak. Specimen 226 shows such a condition (fig. 4).
The germ cells probably have no relation to the mesoderm cells,
but have only temporarily wandered among them. By the
time the stage represented in no. 276 (fig. 5a) is reached a condi-
tion in which the embryonic rudiments lie as ‘slipper shaped’
structures each at the terminus of an elongated canal—the
germ cells are becoming fairly well established in the entoderm
of the embryos which are now in a relatively advanced primi-
tive streak stage. The position of the cells may be seen from an
examination of figure 5a.
As the primitive streak advances, the entoderm previously
seen as a straight ribbon of cells, now commences to thicken and
push down and inward to form the intestinal groove. The germ
cells, which by this time have all migrated into this layer, are
GERM CELLS IN TATUSIA NOVEMCINCTA 351
carried along in the lateral surfaces of the primitive intestine.
There seems to be no evidence whatsoever, in the armadillo,
of germ cells ever entering into the mesoderm or its forming blood
vessels, as described by Swift in the chick. Since Swift’s work
is not only able but convincing, it merely remains to be said
that the paths of migration in birds and in this mammal differ.
It seems certain that the germ cells of the armadillo, passing
Text fig. B A reconstruction of specimen 290 (taken from Patterson, ’13),
showing the location of germ cells at this period. The dotted lines indicate the
plane of the sections, in which germ cells were found at points (2).
along the blastocyst entoderm into the embryonic entoderm,
become immediately incorporated in the intestinal wall without
ever being seen to pass through the mesoderm at all. Of course
this is no new thing in mammalian work, since Fuss (’12) and
Rubaschkin (’08) have described similar conditions in the
rabbit and pig. My observations seem merely to confirm those
of Fuss on this point.
From the time of the late primitive streak up until a stage
where the embryo shows a well-developed cervical flexure (figs.
6a, 7a, 8a), the germ cells remain in the intestinal entoderm.
352 AIMEE S. VANNEMAN
During this time they seem to be traveling ventrally in the
intestine and are distinctly amoeboid in shape (fig. 8). They
are elongated and appear to be slightly smaller than before, due
no doubt to the crowding among large entodermal cells. At
no time during the history and development of the armadillo
have germ cells been found in the blood vessels. Figure 6 shows
the position of the germ cells in the seven, ten, and fourteen
somite stages. A drawing of the three somite stage was not
made, as the position of the germ cells here was almost identical
with their position in the primitive streak stage before somite
formation. Further description of this period of germ cell his-
tory is unnecessary. In the 4-mm. embryo, however, the germ
cells begin to leave the intestinal entoderm, as shown in figure
9a. Superficially, the 4-mm. embryo is characterized by the
acute cervical bend and prominent heart regions, but as yet
shows no external signs of limb buds. It is at this stage that
germ cells are first seen to be massing along the ventral wall of
the now-closed intestine. Certain it is that germ cells are still
to be seen in the lateral walls of the intestine, but their number
is small (observe fig. 9). It will be noted from this same figure
that a couple of germ cells are in the process of passing out of
the intestinal entoderm, while one cell is already visible within
-the loose surrounding mesenchyme, which shortly will go to
form a part of the permanent mesentery. ‘This is a critical
stage, and interesting because it so clearly presents the pass-
age of the germ cells from the entoderm into the mesoderm.
The next stage in my possession is the 5.5 mm. embryo which
externally shows well developed limb-buds. The examination
of sections reveals the presence of germ cells in a well-developed
mesentery. What course is followed by the germ cells in reach-
ing this location cannot definitely be stated in the absence of an
intervening stage. However, with ones knowledge of the for-
mation of the mesentery it is not difficult to conceive of how this
might happen. It is probably not amiss to say that, as the
intestine continues to round up, the germ cells which have mi-
grated into the loose mesenchyme around the intestine pass up
and forward, through a process of growth and shifting of the
GERM CELLS IN TATUSIA NOVEMCINCTA aoe
tissues, and also through their independent amoeboid move-
ment into the forming mesentery. The germinal epithelium is
present on either side of the mesentery (fig. 10a), but as yet no
thickening has occurred to form the lateral ridge. The germ
cells at this time are found in equal numbers in three places.
They can be seen located between the blood vessels of the mesen-
tery as seen in (fig. 106), but are never found at this time in the
mesentery below the level of these vessels. The germ cells may
also be found at the angle of the mesentery and the germinal
epithelium (fig. 10). The cell seen in figure 10 is unusually
large and therefore not quite typical. A number of germ cells
seem to pass dorsal, above the root of the mesentery and of the
region of the germinal epithelium, into the loose mesenchyme
beneath the aorta. Strangely enough, at this period the cells
are not particularly amoeboid in shape (fig. 10). It is notice-
able, also, that they are larger than usual. In addition, the
nucleus instead of being granular has become more or less reticu-
lar in appearance. While the germ cells are traveling into the
germinal epithelium, the latter thickens and germ cells become
embedded in it. The germ cells are very easily distinguished
from the peritoneal cells among which they lie (fig. 11), so that
it is impossible to believe that they could ever be derived from
these cells.
By the time the embryo is 10 mm. long, the germ cells have
all migrated into the well-developed indifferent gonad (fig. 11).
At this time as seen from the drawing they are very conspicuous
for their size. The apparent increase in size is due, no doubt,
to the fact that the cells are preparing for division.
DISCUSSION
The migration of the germ cells from the entoderm to the sex
anlage is unmistakable. Throughout, the germ cells can easily
be followed. But the question as to the origin of these same
cells remains somewhat doubtful, although the writer is of the
opinion that the conclusions reached in this paper are of rather a
convincing nature. The examination of stages now at hand has
354 AIMEE S. VANNEMAN
brought out several interesting facts which suggest reasonable
conclusions as to the origin of the germ cells in the armadillo.
It was pointed out in the first part of this papers that no germ
cells of the character of those seen in later stages could be found
in the wall of the early ectodermic vesicle, a stage which long
precedes the laying down of any embryonic primordia. It was
thought that possibly such a stage might reveal a definite point
along the vesicle wall, where germ cells might be seen to be
localized, previous to scattering and migrating into the future
embryos. In this sense, one might attribute, in a polyembryonic
form, a common origin to the germ cells of all the embryos of
one vesicle. This, however, not proving to be the case, an ex-
amination of the vesicle next in order of development—that is, a
stage where the very beginnings of lateral plates can be dis-
cerned—revealed the following fact: that there exist several
germ cells lying close along the entoderm wall of the vesicle
outside the region of the primary buds. The cytological re-
semblance of these cells to adjacent entodermal cells, and the
presence of a dividing cell at once suggests the possibility that
here, for the first time, germ cells are being proliferated. But in
the two primary bud stages examined, there were found present
in each blastocyst no more than two germ cells. This condition
is in contrast to that of the secondary bud stage when the germ
cells are relatively numerous in the region of each of the newly
forming embryos. The germ cells of each quadruplet all at once
become visible in the respective embryonic areas, without hav-
ing been seen to migrate there—except for the few cells seen
traveling between the embryonic areas of specimen 290 (text fig.
2). As was mentioned earlier in the paper dividing cells are not
infrequent during this period. A consideration of all observations
would point to the fact that active germ cells do not arise, at
least in any numbers, until the secondary bud stage is reached.
The few germ cells appearing before this time may be said to
have arisen more or less accidentally in anticipation of the later
stage. Some of these cells doubtless migrate towards the em-
bryonic areas; others, however, probably degenerate. Cer-
tainly their number is too few to warrant the belief that all the
GERM CELLS IN TATUSIA NOVEMCINCTA 355
germ cells of the future embryo arise before the appearance of
embryonic primordia. Indeed, I believe that these early germ
cells play but a feeble réle in the origin and future history of the
germ cells. Therefore, while recognizing that stray germ cells
may be found as early as the young primary bud stage, the
writer believes that the active germ cells of embryonic life arise
for the most part at the very early primitive streak stage of the
embryos. Such an origin for germ cells isin general, similar to
Swift’s findings in the chick, both as regards place, method and
time. The entoderm of the mammalian blastocyst is analogous
to the yolk sac entoderm of lower vertebrates. It is not un-
reasonable to suppose that in the armadillo the germ cells arise
during the secondary bud stage in the embryonic areas through
the influence of the ectodermic vesicle upon the blastocyst ento-
derm at the point where the two layers come in contact. Ob-
servation seems to confirm this. That the germ cells have
not arisen in numbers any earlier may be due to the fact that
there exists previous to the early primitive streak stages no inci-
dent, such as the coming in contact of ectodermic and ento-
dermic layers, to favor the proliferation of germ cells.
SUMMARY
1. The germ cells of the armadillo are conspicuously large,
and first discernible along the entodermic wall of the blastocyst,
just preceding the primary bud stages. They are extremely
few in number. The active, embryonic germ cells, however,
probably do not arise until the time of the secondary bud stage
appearing in the vicinity of each of the four embryonic areas.
2. During early primitive streak stages germ cells are seen
dividing, previous to pushing a way into the entoderm of the
future gut region.
3. After gaining entrance into the gut entoderm, the germ
cells are carried in the thickening intestinal wall as, during the
somite stages, it rounds up to form a closed tube.
4. By the time the embryo has attained a length of 4 mm.
and has a pronounced cervical bend, the germ cells may be seen
356 AIMEE S. VANNEMAN
in the act of leaving the ventral, intestinal wall to enter the
surrounding mesenchyme tissue. They are amoeboid in shape.
5. In the 5- and 6-mm. embryos, the germ cells appear at
the base of the well-developed mesentery, usually not below the
level of the three blood vessels of that region. They are also
present in the loose mesenchyme under the aorta, and en route
to the germinal epithelium, which has not yet thickened.
6. In the 10-mm. embryo, the germ cells are established in the
indifferent gonad. They are slightly enlarged, preparatory to
division.
7. A study of early stages suggests that germ cells may arise
from certain cells of the blastocyst entoderm (yolk-sac entoderm)
during secondary bud formation.
8. The path of migration is from the embryonic entoderm into
the intestinal wall, thence into the surrounding mesenchyme to
the mesentery, and onward into the germinal epithelium. No
germ cells are found at any stage in the blood vessels.
9. It may be concluded that the germ cells of the four em-
bryos of one vesicle do not have a common origin, in the sense
of having arisen from a prelocalized region of the early plastocyst.
BIBLIOGRAPHY
ALLEN, B. M. 1906 The origin of the sex-cells of Chrysemis. Anat. Anz.,
Bd. 29. ‘
1907 An important period in the history of the sex-cells of Rana
pipiens. Anat. Anz., Bd. 31.
1911 Origin of sex-cells of Amia and Sepidosteus. Jour. Morph.,
vol. 22.
Bearp, J. 1900 The morphological continuity of the germ cells of Raja bates.
Anat Anz., Bd. 18.
1902 The germ cells of Pristuirus. Ibid. 21.
BERENBERG-GossLER, H. von 1912 Die Urgeschlechtszellen des Hiihner-
embryos u.s.w. Arch. Mikr. Anat., Bd. 81.
Dopps, G. 1912 Segregation of the germ cells of the teleost Sophius. Jour.
Morph., vol. 21.
EIGENMANN, C. 1896 Sex diierentiation in the viviparous teleost Cymato-
gaster. Arch Entwich., Bd. 4.
Frprrow, V. 1907 Ueber die Wanderung der Genital-Zellen bei Salmo Fario.
Anat. Anz., 31.
Fuss, A. 1912 Ueber der Geschlechtszellen der Menschen und der Saugetiere.
i Arch. Mikr. Anat., Bd. 81.
GERM CELLS IN TATUSIA NOVEMCINCTA 307
Heener, R. W. 1909 The origin and early history, of the germ cells in some
chrysomelid beetles. Jour. Morph., vol. 20.
1914 Studies on germ cells. Jour. Morph., vol. 25.
1915 Studies on germ cells (continued). Jour. Morph., vol. 26.
Jarvis, May 1908 Segregation of germ cells of Phrynosoma cornutum. Biol.
Bull., vol. 15.
Keuuicort, W. 8. 1913 A Text-Book of General Embryology.
Monteomery, T. H. 1911 Differentiation of the human cells of Sertoli. Biol.
Bull., vol. 21. :
Newman, H. H. anp Patrrerson, J. T. 1910 Development of the nine-banded
armadillo from primitive streak stage to birth; with especial refer-
ence to the question of specific polyembryony. Jour. Morph., vol. 21,
no. 3.
Patterson, J. T. 1913 Polyembryonic development in Tatusia novemcincta.
Jour. Morph., vol. 24, no. 4.
ReAGEN, F. P. 1916 Some results and possibilities of early embryonic castra-
tion. Anat. Rec., vol. 11, no. 5.
RuBAscHLiIn, W. 1908 Zur Frage von der Entstehung der Keimzellen bei
Saugetieren Embryonen. Anat. Anz., Bd. 31.
ScHapitTz, R. 1912 Die Urgeschlechtszellen von Amblystoma. Arch. Mikr.
Anat., Bd. 79.
Swirt, C. H. 1914 Origin and early history.of the primordial germ cells in the
chick. Am. Jour. Anat., vol. 15.
1916 Organ of sex-cords and definitive spermatogonia in male chick.
Am. Jour. Anat., vol. 20, no. 3.
Tscuascutn, S. 1910 Ueber die Chondriosomen der Urgeschlechtszellen bei
Voégelembryonen. Anat. Anz., Bd. 37.
Wikre, G. 1912 Zur Frage nach der Herkunft der Mitochondrien in den
Geschlechtszellen.
WINIWARTEN, H. von 1901 Richerches sur l’ovogenise et l’organogenese des
Mammiferes. Arch. Biol. T., 17.
Wireman, H. L. 1910 A study of the germ cells of Septinotarsa signaticollis.
Jour. Morph., vol. 21.
Woops, F. A. 1902 Origin and migration of the germ cells in Acanthias. Am.
Jour. Anat., vol. 1.
THE AMERICAN JOURNAL OF ANATOMY, VOL. 22, NO. 3
The drawings were made at table level with a Spencer camera lucida. For
the detailed drawings ocular 6 and Spencer 1.5 mm. apochromat N. A. 1.30 ob-
jective were used. For figures la to 1la ocular 2 and 16 mm. apochromat N. A.
0.30 objective were employed. For the most part the drawings were made from
sections 8 to 10 micra thick.
PLATE 1
EXPLANATION OF FIGURES
1 Section through specimen 256 (early primary bud stage) showing a germ
cell lying between entodermic and ectodermic layers. The rectangle repre-
sented as figure 1a indicates the area from which this drawing was made.
2 Detailed drawing from the area indicated in figure 2a (primary bud stage)
showing a germ cell and a large dividing cell joined to the entoderm by a thin
strand of tissue.
3 Detailed study from specimen 290 (early secondary bud stage) showing
germ cells lying close to the entoderm among stray mesoderm cells of the primi-
tive streak area.
4 Later secondary bud stage showing a section through one of the buds
(fig. 4a).
358
GERM CELLS IN TATUSIA NOVEMCINCTA
AIMEE S. VANNEMAN
309
PLATE 1
PLATE 2
EXPLANATION OF FIGURES
5 Section through specimen 276 to show the position and detail of germ
cells in the area indicated in figure 5a.
6 Detailed study of a section through the posterior third of a seven somite
embryo showing germ cells in the gut entoderm. The condition in the three
somite stage is similar.
7 Section through the primitive intestine of specimen 449 (10 somite stage)
depicting the position of the germ cells, and the comparative size of germ cells
and erythrocytes. Refer to figure 7a for orientation.
8 Section through the gut region of specimen 365 (14 somite stage) showing
the amoeboid shape of the germ cells at this time. The rectangle in figure 8a
roughly indicates the area from which the drawing was made.
360
GERM CELLS IN TATUSIA NOVEMCINCTA PLATE 2
AIMEE S. VANNEMAN
r
361
PLATE 3
EXPLANATION OF PLATES
9 Section through the closed intestine of a 4mm. embryo. Note that two
germ cells have already left the intestinal entoderm. See corresponding sketch
(fig. 9a).
10 and 106 Representing two detailed studies from the area indicated by the
rectangle in figure 10a. (Transverse cut through 6 mm. embryo.) Figure 10
shows a section through the germinal epithelium. Figure 10b represents a sec-
tion through the base of the mesentery. Note the enormous size of the germ
cells.
11 Representing a section through the well developed indifferent gonad of
the 10 mm. embryo. The portion of the gonad is indicated by the letter g in
the corresponding sketch (fig. 11a).
362
GERM CELLS IN TATUSIA NOVEMCINCTA PLATE 3
AIMEE S. VANNEMAN
“o) 9 yt om BF wee se 3
Ea
ef yh
AUTHOR’S ABSTRACT OF THIS PAPER ISSUED
BY THE BIBLIOGRAPHIC SERVICE CCTOBER 27.
THE DEVELOPMENT OF THE SEROUS GLANDS (VON
EKBNER’S) OF THE VALLATE PAPILLAE IN MAN!
EK. A. BAUMGARTNER
Department of Anatomy, Washington University Medical School, St. Louis
ONE TEXT FIGURE AND THREE PLATES (TEN FIGURES)
INTRODUCTION
In 1873 von Ebner described the acinal glands in the base of
the tongue. Since then contributions to our knowledge of these
glands have been mainly of a topographical or comparative
nature. Surprisingly little work has been done on the develop-
ment of the lingual glands. Griberg’s (98) figures of sections
showing the early origin of the serous glands of the vallate
papillae in man form the basis of the description of the develop-
ment of the serous glands in Keibel and Mall’s Embryology. He
figured them as early lateral outgrowths from the epithelial
walls of the papillae which in later development branch consider-
ably but are not fully developed in a 56 em. child. This work,
together with Oppel’s (99) excellent figure of the topography
of the lingual glands in various mammals, is particularly en-
lightening. Oppel’s study of the arrangement of the lingual
glands in man is based upon a single specimen. Maziarski (’01)
gives a brief illustrated description of a model of a small portion
of the glands of a child of fourteen years.
Since there has been so little work done on the development
of these glands and on their adult condition, an intensive study
of the glands in various stages of development as well as a fur-
ther inquiry into their topographical distribution in late fetuses
and the newborn, may be of interest. The topographical dis-
tribution in the newborn, the arrangement of ducts and gland
1T wish to thank Prof. J. Playfair MeMurrich for the privileges of his lab-
oratory during a part of the time while this study was in progress.
369
366 E. A. BAUMGARTNER
masses, the distribution of blood vessels and the topographical
relations of ducts, glands and blood vessels are considered in
this study.
The greater part of the material used was preserved in forma-
lin. Serial sections of the entire caudal region of the tongue
of the younger fetuses form the basis for the study of the glands.
Wax reconstructions of various stages of glandular development
were made according to Born’s method.
DEVELOPMENT OF THE GLANDS
As indicated by Griberg, the vallate papillae first appear as
solid epithelial downgrowths. <A surface view of the tongue of
a 6.5 em. fetus shows no papillae under a low power lens al-
though the foramen caecum is well developed. However, sec-
tions show seven papillae, well defined by epithelial down-
growths. Their arrangement is characteristic. No glandular
outgrowths are distinguishable.
The earliest glandular outgrowths from the epithelium appear
in an 8.5 em. fetus. There are nine well developed papillae, the
fifth lying in the foramen caecum and forming the apex of the
‘V. As yet there are no grooves outlining the papillae. <A
reconstruction of the anterior papilla of the right side shows a
slight indication of a groove surrounding it and the papilla
slightly raised above the surface of the tongue. The anlagen
of four glands project from the lower border of the epithelial
wall, two occupying a lateral position and two a medial (fig. 2).
The caudo-lateral anlage is ridge-like with two protruding ends;
the antero-lateral and the caudo-medial are rounded elevations;
and the antero-medial has two slightly extended ends.
Several bulb-like outgrowths are found on the lower border
of the epithelial wall of a vallate papilla from a 9 em. fetus.
Of the eight papillae in the tongue of a 10 cm. fetus the one
in the foramen caecum is the largest. This one and the two
adjoining it on the right side were reconstructed. Deep fur-
rows separate the papillae from each other. Of the three pa-
pillae modeled, the anterior one is divided into four parts by
epithelial partitions. Both the partitions and the surrounding
SEROUS GLANDS OF THE VALLATE PAPILLAE 367
wall bear glandular outgrowths. The second papilla is simple.
Five glands project from the lower border of the epithelial
wall, two of which have enlarged ends and slightly constricted
necks. The third papilla modeled, that in the foramen caecum
(fig. 3) shows many glands at its lower border, some having the
same appearance as the two above described, The lateral walls
of this papilla also bear gland anlagen resembling in some cases
folds of epithelium.
Nine papillae are present in an 11.5 em. fetus. One papilla
on the left side, near the foramen caecum, was reconstructed.
Most of the glands extend downward and slightly caudalward.
Three glands (fig. 4) are longer than the others, the constricted
necks having apparently elongated. Gland anlagen are to be
found on the outer surface as well as on the lower border of the
epithelial wall.
The tongue in a 12.5 cm. fetus shows twelve papillae. In
sections, a very slight furrow is present indicating the site of
the developing groove. This groove is only indistinetly indi-
cated in a model of the two right anterior papillae. A model
of one of these papillae, with its glands, is shown in figure 5.
The glands are elongated greatly, their ends are enlarged and
the stalks constricted. The stalks and occasionally the bulb-
like ends have lumens. The walls of the ducts are formed by
two rows of epithelium but the walls of the bulbous ends contain
four or five rows. In both of the papillae modeled the greater
number of glands are found at the anterior and posterior ends.
These glands are longer than those at the sides. Five of the
nineteen glands arise from the outer wall, one from the inner,
and the remaining thirteen from the lower border of the epithe-
hal wall of the papilla. Two of the caudal glands have arisen
so close to each other that they give the appearance of branches
from a single outgrowth. The larger of these glands divides
almost immediately, one branch extending caudalward almost
in a horizontal plane, the other extending downward and caudal-
ward for a short distance, then again dividing. At the pomt
of the latter division, the duct is somewhat enlarged and has a
well-defined lumen. The two subdivisions project straight
368 E. A. BAUMGARTNER
downward, one sending off a short caudal branch. From the
origin of the caudal branch, the duct enlarges gradually up to
the end piece.
The condition just deseribed seems to be true of all of the
longer glands. ‘That the end pieces are distinctly enlarged is
apparent in sections as well as in reconstructions (fig. 5). The
glands of the papilla occupying the foramen caecum are more
highly developed than those of the other papillae, as evidenced
by more branching and the greater length of the ducts.
Nine vallate papillae are present in the tongue of a 15 em.
fetus. Reconstructions were made of the two anterior papillae
on the right side. In one a very long gland extends deeply into
the tongue (fig. 6). At its origin from the lower border of the
wall of the papilla two short glands are found. The long gland
extends downward about 0.5 em. then divides into two branches.
Both of these subdivide, a subdivision of each branch going
lateralward. All carry enlarged knob-hke masses at their ends.
These show beginning subdivision into several parts. About
0.15 mm. from its origin, several branches are given off from the
long gland. The latter show small rounded masses constricting
from the end bulb of each (fig. 6).
Other glands of the same papilla are short and show occasional
anlagen of lateral branches on the stalks. Some small glands,
without terminal enlargements, are present on the lateral walls
of the papilla.
A tongue from. a specimen slightly smaller than the previous
one (14.5 em.) also has nine papillae. In this and other speci-
mens, some papillae, when examined under low power lenses,
appear to consist of several small, closely crowded papillae en-
closed by one turrow. The condition described in the 10 em.
fetus, viz., epithelial downgrowths subdividing the papilla into
smaller, closely associated ones, is found here. Four of the
nine papillae in a 14.5 em. specimen were of this compound form,
and for the first time, a well-formed surrounding groove is pres-
ent. The papillae are somewhat raised above the level of the
dorsum of the tongue. A reconstruction of the right anterior
papilla shows fourteen glands in various stages of development.
SEROUS GLANDS OF THE VALLATE PAPILLAE 369
They are more branched than those of the 15 cm. specimen
studied, this being particularly true of the terminal portions
of the ducts. The gland ducts frequently divide dichotomously,
although occasionally they resolve into three or four branches.
Some of the glands extend down into the muscular tissue as
far as the transverse muscle layer, where they spread into ter-
minal branches. The terminal branches, as a rule, run hori-
zontally, sometimes with many turns. A few, however, are so
situated that their secretions are emptied into the main duct
against its stream. The three largest glands of the papilla
occupy a medial position. One of these shows especially well a
terminal arborization similar to that seen in figure 6, as well as
beginning alveolar subdivision of the end masses. In the
shorter glands the end pieces do not show as yet this formation
of alveoli. Only two glands arise from the outer wall of the
papilla. Another, possibly the anlage of a mucous gland, has its
origin from. an epithelial fold lateral to the papilla. It shows,
however, the same terminal enlargement as is characteristic of
the glands of the vallate papilla.
One papilla of a specimen 19 em. long was reconstructed.
This specimen was singular in that it presented so many gland
ducts to each papillae. The papilla chosen for reconstruction hes
on the left side near the foramen caecum. With this papilla
seventy-seven ducts are associated, while with another papilla
on the left side, one hundred and four are present. In the one
reconstructed, two glands avise from the inner wall of the papilla,
the others coming from the lower border and outer wall. Some
ducts are 2 mm. long, others very short. The short glands are
characterized by short side branches and enlarged end pieces
(fig. 7). The breaking up of the end pieces is advanced far be-
vond that in younger specimens and is apparently a constricting
of parts to form small round, or ridge-like alveoli, the latter
connected by a long narrow base. Older stages demonstrate
that these may first separate in the middle, having the ends
attached, and thus form anastomosing alveoli. The serous
glands of the vallate papillae can, therefore, in later fetal stages,
be considered as branched alveolar glands. Both the end
370 E. A. BAUMGARTNER
pieces and the stalks have lumens. In another specimen 19
em. long, a spherical thyroid-like mass is present in the base
of the tongue above the hyoid bone. It is made up of follicles
which contain a colloid-like substance. No connection between
this mass and any duct system is apparent.
Sections of a tongue of a 23.5 em. fetus show twenty-six and
forty ducts respectively in connection with the first and third
papilla on the right side. The second papilla on the left side
is provided with forty-five ducts. One of the ducts in this
specimen has a greatly dilated end from which small ducts
radiate in all directions. This cystic enlargement, irregular in
shape, is lined by a layer of flattened epithelium and measures
0.6 by 0.4 by 0.15 mm. in its greatest diameters.
The vallate papillae of a fetus 25 cm. in length, of a new
born, and of a nine months old child, all show the characteristic
short and long glands sending off many branches with terminal
arborization of alveolar-like glands with occasional anastomoses.
The longest ducts extend into the upper strata of the trans-
verse muscle, the gland masses being broken up by the vertical
and the longitudinal muscle fibers. A small group of glands
in the tongue of the nine months old child were modeled (fig. 8).
Some of the glands are irregular in shape, showing constrictions,
outpouchings and anastomoses. The method of formation ap-
parently is as previously described. The main ducts fre-
quently present many small, solid outpouchings, the anlagen of
other gland groups. Two such anlagen attached to the large
duct near the gland appear in the model (fig. 8).
Two papillae in a newborn have associated with them thirty-
eight and forty-three ducts respectively. In another specimen
three papillae have thirty-two, thirty-three, and thirty-eight
ducts respectively. One of the latter with its gland groups,
from the caudal end of a papilla, was reconstructed. Twenty-
one groups of glands are attached to this main duct by means
of small lateral or terminal branches (fig. 1). The gland masses
extend beyond all sides of the papilla, spreading antero-poste-
riorly 2.2 mm., laterally 1.8 mm. and projecting into the tongue
tissue about 1.2 mm. Since the antero-posterior diameter of
SEROUS GLANDS OF THE VALLATE PAPILLAE ol
this papilla is only 0.5 mm. and the lateral diameter 0.56 mm.,
one can readily see that there must be great intermingling of
glands when there are thirty or forty such ducts, or one hundred
as was found in a younger specimen (19 cm.).
A graphic reconstruction from the newborn to show the posi-
tion of the papillae and the distribution of the serous glands
resembles in all respects the reconstruction of Oppel (99).
Since the glands of the newborn are not of the branched,
tubular type of the child of fourteen years as modeled and de-
scribed by Maziarski, reconstructions of glands from specimens
Fig. 1 Drawing made from a photograph of a reconstruction of a papilla
and one duct with its gland groups from a newborn. X 65.
of intermediate ages were made in order to determine the char-
acter of the transition between these forms. From a reconstruc-
tion of a small group of glands of a nine months old child it
appears that these resemble closely those of the newborn (fig. 8).
The alveolar masses occasionally anastomose although this may
not be apparent from a surface view. As stated above the
method of development readily accounts for this anastomosing
of end-pieces. In the newborn and nine months old child, the
larger ducts frequently present small irregular outpouchings
connected by short, constricted stalks. Some of these show the
beginnings of secondary alveolar-like sacs. These groups may
develop into glands similar to those already formed, or remain
in a more or less undeveloped state.
372 E. A. BAUMGARTNER
In the specimen from a child of five years, as also in speci-
mens from older individuals, mucous glands, either as single
alveoli or in groups, join the ducts of serous glands. Occasion-
ally a part of an alveolar group is formed of serous cells, which
are succeeded by cells distinctly mucous in type.
A reconstruction of the glands from a twenty-two year old
specimen shows anastomoses between the closely crowded alveoli.
Some of the glands are somewhat tubular, although they gen-
erally appear to be more of the alveolar type (figs. 9 and 10).
The main ducts are distinctly different in structure from the
end pieces, but the terminal ducts, breaking up within a group
or lobule, may be similar to the glandular end-pieces. Anasto-
moses occur between alveoli of two terminal ducts as well as
between those from one duct (fig. 9). Irregular outgrowths
of the main ducts noted in younger specimens are present also
in this specimen; these outgrowths extend in every direction
and some are just beginning to break up into end-pieces (fig. 9).
Figure 9 shows a gland from one terminal duct anastomosing
with one of these gland anlagen. The lumen in the specimen
could not be traced from one duct to the other through the gland
mass. However, the lumens are sometimes very minute, even in
larger end-pieces. Figure 10a shows an alveolar-like end-
piece connected with the terminal duct; from the former three
alveolar-like end-pieces project in various directions. Figure
10 shows a group of glands from which a portion has been re-
moved in order to show the terminal duct with its various
end-pieces.
The histological structure of the serous glands from the
twenty-two year old specimen varies greatly. In some of the
glands the secreting cells are large and deeply-stained; in others
the lumens are large, whereas the cells appear flattened. These
differences are probably due to different stages of functional
activity.
Serial sections of a vallate papilla from a man fifty years old
presented very closely crowded glands.
Although this work is mainly a study of the development of
the serous glands and their topographical relations, some at-
SEROUS GLANDS OF THE VALLATE PAPILLAE 373
tention is given to their histological structure, especially in the
better preserved material from older individuals.
An attempt to include the taste buds in the models was met
with only partial success. Few taste buds appear in stages
before that of the 19 cm. fetus, but in this specimen the number
is relatively large. In all cases taste buds are more numerous
on the sides of the papillae although some are present on the
summit. They are also found on the dorsal surface in the
newborn. In none of the specimens is there any definite ar-
rangement of the taste buds in rows and tiers as has been
described in sheep and pig by Schwalbe (’68).
In several specimens the lingual artery was injected and the
materia) sectioned and studied. A number of rather large ar-
teries ascend obliquely toward the serous glands about the
vallate papillae. Smaller vessels enter a’ group of glands and
then subdivide. Some of the latter vessels leave the glandular
tissue and supply the surrounding musculature. The arteries
do not follow the main ducts, or the terminal ducts of the
lobules.
DISCUSSION
As has been stated, the earliest glands are downgrowths of the
lower border of the papilla. Griiberg (98) figures the first out-
growths from. the lateral wall of the papilla. My models show
that lateral outgrowths are not infrequent but that the gland
anlagen which first appear in about 8.5 em. fetuses are on the
lower border (fig. 2) of the papilla. Oppel (99) gives us an
excellent figure showing the topography of the serous glands.
The conditions there shown are confirmed in the present study
of the serous glands in a newborn. These glands extend 3-5
mm. on all sides of the vallate papillae as has been observed
by Oppel and by von Ebner (’73). The extent of the area occu-
pied by the group of serous glands about a papilla can be esti-
mated by reference to figure 1 which shows a single duct with
its gland groups. With thirty to fifty such ducts associated
with a papilla it is apparent that the glandular tissue must be
crowded and extend considerably beyond the surrounding fur-
THE AMERICAN JOURNAL OF ANATOMY, VOL. 22, NO. 3
’
374. E. A. BAUMGARTNER
row. I have not*found glandular tissue within the connective
tissue of any papilla although von Ebner and others have noted
this.
The ducts open into the bottom of the furrow or along the
lateral side of the epithelial wall, and occasionally into the
medial wall. No ducts are observed opening into the dorsum
of the papilla or into other grooves in the surface of the tongue
(except those belonging to the folliate papillae). Nor are any
ducts lined by ciliated epithelium as described by Schwalbe
(68), von Ebner (73) and*Gmellin (92) found in my material.
Von Ebner stated that small alveoli either poorly developed or
not fully formed, and separated by considerable connective tissue
are not infrequently present. It is apparently such a group of
glands which Maziarski (’01) has reconstructed and figured. In
my material I have seen such a condition in only one group of
glands from a five year old child, and in this it is rather that
considerable connective tissue separated the more or less tubulo-
alveolar components of the glands than that the glands them-
selves are small. This group of glands approaches the alveolar
‘type more nearly than does the one figured by Maziarski and
as in his, no anastomoses are present. For the most part,
although the lobules may be closely crowded or scattered, the
individual end-pieces are usually very much crowded, and as a
result are often rounded or irregular in shape. ‘This fact. may
account for the occasional anastomosing of glands observed in
my material. It is possible that the anastomoses are not per-
manent and that anastomosing end pieces may separate in older
specimens. Absence of lumens in these anastomoses may indi-
cate beginning separation. However, as stated, the lumens are
often very minute and may appear discontinuously in other
places.
Simple outgrowths from larger ducts are present in several
of the specimens studied (figs. 8 and 9). That these are gland
anlagen seems probable since various stages from the earliest
outpouchings to those showing beginning glandular division are
present. The serous glands therefore are not fully developed
SEROUS GLANDS OF THE VALLATE PAPILLAE oD
at birth nor even at five years. At twenty-two years simple
outgrowths and anastomoses are still present (fig. 9).
Schmidt (96) and Erdheim (’04) have described several
cases In which cystic glands are found associated with the thy-
reoglossal duct, or, as isolated structures containing no ducts.
In the present study, the occurrence has been noted of a spheri-
cal, thyroid-like mass, made up of follicles and containing a
colloid-like substance, situated in the base of the tongue of a
19 cm. specimen. In another specimen dilatations of the ducts
of some of the serous glands of the anterior papillae have been
observed. A homogenous mass filled the cystic parts, and a
duct connected the largest cyst to the groove surrounding the
papilla. It appears, therefore, that besides the cystic glands
associated with the thyreoglossal duct, cystic enlargements of
serous glands of the tongue might also occur.
Frequently taste buds are found on the dorsal surfaces of the
vallate papillae in the newborn. In other specimens they are
noted only incidentally and occasionally are reconstructed with
the papillae. It has been stated above that in some of the
newborn and older specimens, mucous glands intermingle with
serous glands and join with the ducts of the latter. This condi-
tion has also been observed by Maziarski and others. It is
possible therefore that the ducts and glands of the vallate pa-
pillae although usually serous in type are capable of developing
mucous cells or alveoli or of being transformed into mucous
alveoli, or that secondary connections are established between
mucous end-pieces and the ducts of serous glands. It is note-
worthy that mucous alveoli joined to ducts of the serous glands
are observed only in adult material.
From the distribution of the blood vessels in the gland groups,
it does not appear that the latter conform to our usual concep-
tion of lobules or histological units of organs.
CONCLUSIONS
Serous glands first appear in 8.5 cm. fetuses as outgrowths,
originating usually from the lower border, but sometimes from
the outer wall of the vallate papilla.
.
376 E. A. BAUMGARTNER
The first outgrowth is knob-like. Soon a stalk develops
giving rise to lateral branches with enlarged end pieces. In a
19 em. fetus, these enlargements present bulgings of the surface
and beginnings of alveoh. ‘These retain various connections
with the ducts and with each other, so that in the newborn the
serous gland is of the alveolar type with some anastomoses
between the alveoli. In the adult (twenty-two years) some of
the glands are of the tubular type with some anastomoses
between end-pieces of the same and separate ducts.
In the newborn, many knob-like outgrowths appear on the
large ducts; in older specimens the number is less. These out-
growths are probably the anlagen of future glands, or at least
potential anlagen.
Cystic dilatations of the serous ducts may occur.
Mucous end-pieces occasionally open into the ducts of serous
glands of the vallate papillae.
The serous glands of the vallate papillae of man belong there-
fore to the branching tubulo-alveolar and not to the branched
tubular type as stated by Maziarski.
BIBLIOGRAPHY
Von Epsner, V. 1873 Die acinésen Driisen der Zunge und ihre Beziehungen zu
den Geschmacksorganen. Graz.
Erpuerm, J. 1904 I. Ueber Schilddriisenaplasie. II. Geschwiilste des ductus
Thyreoglossus. III. Ueber einige menschliche Kiemenderivate.
Beitr. z. path. Anat. und allg. Path., Bd. 35.
GMELIN, A. 1892 Zur Morphologie der Papilla vallata und foliata. Arch.
mikr. Anat., Bd. 40.
GrABERG, J. 1898 Beitrige zur Genese der Geschmackknospen des Menschen.
Morph. Arb., Bd. 8.
MaztarskI, 8. 1901 Ueber den Bau und die Einteilung der Driisen. Anat.
Hefte, Bd. 18.
McMoraicu, J. P. 1912 In Keibel and Mall, Manual of Human Embryology.
Lippincott, Philadelphia.
Oppget, A. 1899 Zur Topographie der Zungendriisen des Menschen und einiger
Saiigethiere. Festsch. z. 70. Geburtstag von C. v. Kupffer.
Popwisotzky, V. 1878 Anatomomische Untersuchungen tiber die Saiigethiere.
Inaug. Diss. Dorpat.
Scumitrr, M. B. 1896 Ueber Flimmercysten der Zungenwurzel und die driisigen
Anhinge des Ductus Thyreo-glossus. Fesctsch.f. B. Schmitt. Jena.
ScHwaLBe, G. 1868 Ueber die Geschmacksorgane der Siugethiere und des
Menschen. Arch. mikr. Anat., Bd. 4.
PLATES
PLATE 1
EXPLANATION OF FIGURES
2 Ventral view of a reconstruction of the right anterior papilla of an 8.5
em. fetus showing gland anlagen from the lower border of the papilla. X 135.
3 Same view of a reconstruction of the papilla from the foramen caecum of
a 10.0 em. fetus. X 135. ae aise
4 Same view of a model of a papilla of the left side from an 11.5 em. fetus,
showing enlarged end-pieces and constricted stalks. X 135.
378
SEROUS GLANDS OF THE VALLATE PAPILLAE PLATE 1
E. A. BAUMGARTNER
379
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‘ejided sururofpe
oY} WO] Spuv[s owos pus [BA Jo yavd ‘D “CET X ‘SpUB]s 94} JO OOS JO SH][B4S
poyeZuoje pus sooord-pus pesiejus oy} [[ow Ajaepnoyized sMoys STYT, ‘sNyoF “WO
C'ZI & WIT BI[Idvd JomMezUY YYBII oY} JO UOTJONAPSMODEL B FO MOTA [BIFUSA
SaundIg JO NOILYVNVIdxa
6 ALVId
380
PLATE 2
SEROUS GLANDS OF THE VALLATE PAPILLAE
BE. A. BAUMGARTNER
381
PLATE 3
EXPLANATION OF FIGURES
7 Lateral view of a reconstruction of some short glands from a 19 em. fetus.
<I
8 Reconstruction of a small group of glands connected by a terminal duct
to a larger collecting duct from a nine months old child. X 135.
9 Reconstruction of a small group of glands, a larger collecting duct and a
small simple outgrowth anastomosing with the glands of the group, from an
adult specimen of twenty-two years. X 166.
10 Reconstruction of another group of glands showing alveolar-like end-
pieces from a specimen twenty-two years of age. XX 166. a, alveolar end-pieces
opening through an alveolus into the terminal duct; D, main duct; d, terminal
duct to gland group; g, early gland anlagen from main duct.
SEROUS GROUPS OF THE VALLATE PAPILLAE PLATE 3
E. A. BAUMGARTNER
383
AUTHOR’S ABSTRACT OF THIS PAPER ISSUED
BY THE BIBLIOGRAPHIC SERVICE OCTOBER 20.
ANATOMY OF A SEVEN MONTHS’ FOETUS EXHIBITING
BILATERAL ABSENCE OF THE ULNA ACCOMPANIED
BY MONODACTYLY (AND ALSO DIAPHRAGMATIC
HERNIA)
JAMES CRAWFORD WATT
_ Department of Anatomy, University of Toronto
FOUR TEXT FIGURES AND FOUR PLATES
CONTENTS
GEA DTI Ogee lee Sc dhy Os er ERE 8 So ols Sie eee 385
IBTESCTVia blOMS.< eet re cE IOR coe 6 kotha aie decks ee 386
Rarentalehistoiyaeoescce: See ak ons hed ns fo Se eee ee 386
Bieta appearancere aca. hers os 6c ds an es 080d oe eee 386
TReaio UVa fei tayo} NSIS eM hs Gaodis ob Ce A Ate ae eM Te oar e So Se ieee nome ea eareee 391
irsseenon of leit arms .4sy. ec. ss. sl. os 0 EEG 395
WVITISGLES seas. 5 = ag eS elo sic-s & icles © gle «0 + «5 ce 395
Nerves........ Fe ee Ee PETER cb oc ec odac abeaeseane 409
WiSSE1S Sige acetone 3 CC ht a) MMR ee >. a onc ane alee yates 411
imbryological and general econsiderations. .. ..5<.,.0 92 eee 413
LD Ey CT sea eR CN ae) oO een es fe RRR lio! 3 coco ge oct Oem nee 425
Bd OPED Liha foe eee fSe & cis, bjertiews, 9. «os oe et 428
INTRODUCTION
The foetus forming the subject of description in this paper
exhibits the rare deformity of complete absence of the ulna in
each arm, accompanied by the still much rarer condition of
monodactyly (figs. | to 4). This latter condition is not to be
confused with the relatively common condition of syndactyly,
where more than one digit is present, but they are united by a
web of skin and other tissues. Monodactyly, the presence of
only one digit, is very uncommon, and in a search through
the literature only one case was found that resembles the present
one, and that was presented as a freak exhibit at a medical
society, no anatomical investigation of it having been made.
385
386 JAMES CRAWFORD WATT
I have, therefore, undertaken to work out the special anatomical
details of muscles, vessels and nerves in one of the deformed
limbs, in the hope that light might be thrown on some of the
primitive conditions of these parts, and also with the purpose of
adding a definite and exact contribution to the present inade-
quate knowledge of this abnormal condition. ‘‘Indeed the
inquiry into several types of malformation and structural anom-
aly has repeatedly thrown light not only on the malformation
or anomaly itself but also upon the normal process of develop-
ment the disturbance of which it represents.’’—(Ballantyne).
PRESERVATION
This specimen was not obtained until about one week after
its birth, and in the meantime had been kept immersed by the
undertaker who sent it to us, in an embalming solution which,
as far as can be ascertained, was practically a 10 per cent for-
malin solution. In the laboratory it has been kept in 80 per
cent alcohol. No injection of the blood vessels was attempted,
and though this has added somewhat to the difficulty of dissec-
tion, good results have been obtained.
PARENTAL HISTORY
The parental history, as far as could be ascertained, is prac-
tically negative concerning the deformity in this foetus. The
parents are about twenty-five years of age, in comfortable cir-
cumstances, have good mentality and are free from venereal
diseases as far as known. There have been two miscarriages
previous to this one, with no deformities.
EXTERNAL APPEARANCE
The body of the foetus (figs. 1 and 2) is that of a well de-
veloped child born at the end of the seventh calendar month of
pregnancy. It is well formed, healthy looking, and apart from
the upper limbs has no superficial evidence of abnormality. The
sex is male, and no aberrant development of the external genitals
is present. The back is strongly curved, the head bent forward,
ANATOMY OF A MONODACTYLOUS FOETUS 387
and the legs strongly flexed and drawn up against the abdomen.
On following the line of the vertebral column, a slight scoliosis
is observed in the thoracic region convex to the right.
The whole body is covered with a well developed lanugo
moderately dark in color, and on the head is abundant fine black
hair about 2 em.inlength. Nails are present on all the digits of
both upper and lower limbs, but are yet some gepance from
the extreme ends.
The weight of the child is 1280 grams, and the length from
the vertex of the skull to the ischial tuberosity, measured over
the back, is 325 mm. These measurements correspond fairly
well with figures given by Keibel and Mall (10) and by Me-
Murrich (’15) for the seventh month.
The deformed upper extremities show an upper arm segment
with the forearm flexed upon it and united to it by a web of skin,
a narrow carpal region and a single digit. On the right arm
there is also a single digit located at the inner side of the elbow.
The general resemblance to the wing of a chicken plucked for
cooking is strong, and led to the assertion that the mother’s
fondness for visiting the zoological gardens and watching the
birds was responsible for this deformity, because she had spent
much time in this way during the spring and summer months
of her pregnancy. Maternal impressions have been credited
with many strange and miraculous powers without any rational
basis, and this is surely an example where a credulous imagina-
tion has been led far astray. A mere coincidence has been used
to work out a sequence of cause and effect, and, like much cir-
cumstantial evidence, there is here no basis for the assumption
that the two facts have in truth any association whatever.
Only a very slight knowledge of human embryology is necessary
to shatter the theory in this case. The bird impression, if it
may be so called, seized the mother during the spring and
summer when she had a strong desire to be out of doors. It
may be assumed that the deformity in the limbs was an accom-
plished fact when the limb skeleton was laid down and so was
present at the time of the appearance of ossification in the limbs
in the seventh week of development. Indeed it may even be
388 JAMES CRAWFORD WATT
assumed that the deformity was already established at the time
when chondrification began and its origin is thus carried back to
at least the fifth week and to a time when the mother would just
begin to suspect that she had become pregnant, as her expected
menstrual period would then be a week overdue. No visits to the
zoo were yet thought of, as this was in midwinter, and yet the de-
formity was even then an accomplished fact which future develop-
ment could not alter, but only make more clear and accentuated.
The deformed limbs will now be described in more details
In each arm (figs. 8 and 4) the shoulder and scapular regions
appear normal, but slightly flattened, as though from pressure
from the body lying on its side. The upper arm segment lies
parallel to the long axis of the body, close in at the side, and
appears flattened from side to side so that its mediolateral trans-
verse diameter is only two-thirds that of the dorsoventral. It is
gently tapering in outline, narrowing as the elbow is approached.
The elbow is fairly well rounded, and from it the forearm runs
forward in the same plane as the upper arm and flexed on it at an
acute angle, being maintained in the position by a thick web of
skin extending across the interval between arm and forearm. The
part of the forearm beyond the attachment of the web is rounded,
with its transverse diameters about equal, and tapers gradually
distally. The carpus, metacarpus and the single digit also taper
continuously distally, and are all in a position of partial flexion,
showing marked creases or folds on the volar surface at the line
of the joints. There is a well developed nail on the digit, but
it does not yet reach to or project beyond the end of the finger,
as is the case in a child born at full term.
The left forearm and hand (fig. 3) are in the same plane as the
upper arm and in a position of complete pronation. The hand
lies against the side of the cheek, the palm facing directly ven-
trally. Flexion in this hand is gradual.
The right forearm and hand (fig. 4) are in a position midway
between pronation and supination, a position identical with that
normally assumed when the limb skeleton is first defined (Lewis,
Keibel and Mall’s Human Embryology). The distal end of the
ANATOMY OF A MONODACTYLOUS FOETUS 389
forearm curves somewhat inward and the carpus is sharply
flexed upon it and the hand thus comes to lie across the body
under the chin, with the palm facing caudally.
The left arm has no accessory appendages or indications
of any of the missing parts, but on the right one (fig. 4) there is a
flattened appendage attached by a very short narrow circular
stalk to the medial surface of the forearm almost at the elbow.
This structure widens immediately beyond its attachment, being
much compressed and running back applied against the surface
of the arm, and from the distal part of this broader portion
a narrow finger-like process extends at right angles up in the
line of the limb, pointing toward the hand. This appendage
strongly resembles another digit arising at the elbow.
Measurements of the foetus, and especially of the deformed
limbs are here appended in tabular form:
MVeioiitt Of MOebUS acess. Si cine S455 41 tee eee 1280 grams
Length from vertex to ischial tuberosity .................... 325 mm.
ischial tuberosity-to bend of knee. 2... 0. 0... sanguin meee 80 mm.
Bend sofsknee- tosuiprOr Weel veers. 3 ne 0 a he er 75 mm,
ischial tubetrosityatortip of heel... 2.02555. -5 sae eee loo man.
‘Atilja) @ie Iaxerell r@ Gbisral GinGl rr CbiANG I onsobonaonsoccnccceucacoos (OR Wotan.
Deformed wpper extremities
LENGTHS RIGHT LEFT
Acromion process to point of elbow...................| 82 mm. 74 mm
Point of elbow to distal end of radius................ 57 mm. 52 mm.
Bd-ol reds toplMeemiiip);. o< ia... i. 5+ eee eee 35 mm. 25 mm
Skin web
From point of elbow to free edge.......... Secoal| oi) maida, 37 mm.
Angle of divergence of axis of arm aad foreannn
PASE RUGS Ute renee eRe eRe ares stel doen FAG 2 28 degrees | 24 degrees
JA SCMC KCl TOMUUTINO has Sho cone eenabhans secu ola acd co: 50 degrees | 45 degrees
Extra digit
From pedicle to outer edge of broad portion........ 12 mm.
Outer edge of broad portion to tip of digit.......... 18 mm.
From pedicle straight to tip of digit................. 20 mm.
THE AMERICAN JOURNAL OF ANATOMY, VOL. 22, NO. 3
390 JAMES CRAWFORD WATT
RIGHT LEFT
WIDTHS
D aaa Transverse pa aes ‘Transverse
mm. mm. mm. mm.
AMEAtRA UNA S28). <0. Seca Ae BS 19 30 20
Arm at free edge of skin fold............ 29 16 25 17
Arm one centimetre above elbow........ 27 18 23 17
Forearm where first free.........:....... 14 15 14 13
OBIS OUSha 2 ean oo Necdiarer es a POU WA 12 12 10 8
Digiiataniddle: phalanx... 2 ase Say. 6 5 6 1
Extra digit
Rediclessi.) 20. ee ei ae eee fi 4
Proximal third (metacarpal region)... . 12 6
Middle third (proximal phalanx)...... 7 5
Distal third (distal phalanx).......... 5 4
The only case recorded that closely resembles this one is
one reported by Barabo (’00). The complete description as
given by him follows:
Ferner berichtet Herr Barabo tiber eine eigenartige Missbildungen
an den Armen und Hiinden eines nicht vollstindig ausgetragenen
Kindes. Das Kind, 2800 gm. schwer, 46 cm. lang, war mit Wolfs-
rachen behaftet. Der rechte Oberarm von der Schulter bis zur ELl-
bogenspitze war 7 cm. lang; der Vorderarm bis zum Handgelenk 4 em.
Am Vorderarm war nur ein Vorderarmknocken vorhanden. Von der
Beugeseite des rechten Oberarmes ausgehend lief eine Hautfalte auf
den Vorderarm, die 1 em. unterhalb des Ellbogengelenks inserirte und
den Vorderarm in spitzwinkeliger Beugestellung hielt. An der rechten
Hand war nur ein vollkommen entwickelter Finger und Mittelhand-
knocken vorhanden. Die itibrigen Finger und Mittelhandknocken
fehlten.
Der linke Oberarm zeigt ebenfalls ein Liangenmaass von 7 cm.; der
Vorderarm war 5 cm. lang; die beiden Vorderarmknocken waren nor-
mal entwickelt. Es fehlt ebenfalls die ganze mittelhand. Der Dau-
men, rudimentar entwickelt, sass direct auf dem Handgelenk auf und
war | em. lang und mit dem 4 em. langen Zeigefinger durch Syndaktylie
verbunden. Mittel- und Ringfinger fehlten. Der Kleinfinger war vor-
handen und 4 em. lang.
Der Vortragende lisst die Frage offen, ob die Missbildunge auf
abschniirung durch amniotische Faden oder Hypoplasie zuruckzu-
fiihren sel.
From the above account it will be seen that the right arm
in Barabo’s case shows exactly the same condition of a webbed
ANATOMY OF A MONODACTYLOUS FOETUS 391
elbow, single bone in the forearm and monodactyly, as is shown
in both arms of the foetus described by me. This is an impor-
tant point as it leads to the assumption that this condition is a
very definite one, which although very rare is not purely a
chance occurrence but may have some definite cause. Thus it
would be the concrete indication of the previous working at a
certain particular period of development of some definite
vicious or teratogenic influence.
RADIOGRAPHS
Four radiographs were made of the foetus in the X-ray de-
partment of the Toronto General Hospital. Plates were made
of the whole body from the front and from the side, and also
special ones of each arm from the side. The definition of
structures in the plates was excellent and identification of
various parts was an easy task. Prints made from these plates,
however, were unsatisfactory, since heavy prints intended to
show structures with light shadows made heavier parts a solid
mass of shadow without detail, while light prints did not bring
out distinctly the lighter parts. Three prints of each plate were
made, a heavy, a medium, and a light, and from these and the
plates, the following description has been pieced together. The
illustrations are from actual tracings from the plates and are
designed to show only essential structures.
The radiograph of the left arm (text fig. A and fig. 6) shows a
well-developed scapula of normal proportions, and articulating
with it the humerus, which is fairly heavy and of typical shape.
The upper end is well expanded as is also the lower, but as
might be expected no ossification is yet present in the epiphyses.
The lower end extends almost to the end of the bend of the
elbow, and coming off in front of it is a single bone lying in
the forearm. Owing to the cartilaginous condition of the epi-
physes, no articulation can be demonstrated, only the osseous
tissues showing. That this bone in the forearm is the radius
is quite evident from its shape, the upper end being narrow
and the shaft round above and gradually broadening as it pro-
ceeds distally, the entire bone being also slightly curved in
392 JAMES CRAWFORD WATT
its length. Beyond the radius is a considerable clear interval
including all the carpal and metacarpal region where there is
yet no ossification, but in the single digit a small rectangular
ossification is seen proximally and another occurs distally, these
representing the shafts of the proximal and distal phalanges.
Between the two is a clear space where the still unossified car-
tilage of the middle phalanx lies.
The right arm (text fig. B) presents a few differences from the
left. The scapula and humerus are both typical. The humerus
does not, however, reach as near the point of the elbow as does
Distal phalanx
/ Proximal phalanx
Distal
phalanx
Say Radius
Humerus f Radius
[ay Proximal phalanx ‘
Metacarpal
Ovtline of
extra digit
A B
Text fig. A Sketch from a radiograph of the left arm showing the ossified
portions of the skeleton.
Text fig. B Sketch from a radiograph of the right arm showing the ossified
portions of the skeleton. Note the extra digit at the elbow.
that of the left arm, the end of the radius lying under it instead
of in front of it. The radius is more curved than in the left
arm. No carpal bones yet appear, but in the metacarpal region
there is a small ossification representing the shaft of a single
bone. As on the left side ossifications for the proximal and
distal phalanges are present in the digit, while no middle pha-
lanx yet shows. The proximal phalanx is not as well developed
as on the left side.
The appendage at the elbow on the right limb (text fig. B) is
interesting. Its pedicle appears in the interval between the
humerus and radius and running dorsally in its broad part
ANATOMY OF A MONODACTYLOUS FOETUS 393
is a well marked metacarpal ossification, and at right angles
to this and lying in the narrow digital part of the appendage
is the ossification representing the first phalanx. In the region
of the second phalanx there is yet no bone, while the distal
phalanx is represented by an extremely small centre of ossification.
Some delay is thus evident in the processes of ossification in
these limbs since the appearance of the primary center in a meta-
carpal is usually in the ninth week and for a middle phalanx
about the twelfth week. (Keibel and Mall.)
The skeleton of the lower limb (fig. 5) appears to be normal
except that no middle phalanges yet show ossification. Meta-
tarsals, proximal and distal phalanges are all ossified as are
also the talus and calcaneus. The long bones are normal.
Delay in ossification in the middle phalanges is again evident in
these limbs.
The skull shows no abnormalities, although ossification is
very heavy in the base, especially in the petrous regions and
body of the sphenoid, but the vertebral column and ribs show
some interesting features. The vertebral body (fig. 6) shows
as a transversely oval patch with a small clear spot in the center,
indicating the position of the notochord. The appearance of
the body indicates the occurrence of ossification from bilateral
centers or else from a center indicating a bilateral origin. The
ossified part of the neural arch is still divided into its two halves,
no fusion having yet occurred either with the bodies or dorsal
to the spinal cord. The center in each half of the arch (fig. 5)
is quite distinctly seen lying to the side of the body and on the
thoracic vertebrae well marked transverse processes can also be
seen. In the sacral region the centers for the neural arches are
very insignificant and none are to be seen for the coccyx. The
first three sacral vertebrae show a well marked center of ossifi-
cation (fig. 6) on each side in the lateral mass. There are seven
well marked cervical vertebrae, thirteen thoracic, five lumbar,
five sacral and one coccygeal. The first sacral may be identified
by the presence of the centers in its lateral masses, so that it is
evident that the presacral vertebrae are twenty-five in number
instead of the normal twenty-four. That the supernumary
394 JAMES CRAWFORD WATT
vertebra is a thoracic one is assumed from the fact that there
are the normal number of lumbars and cervicals, all typical of
their region in appearance, and all free from ribs, while between
these regions lie thirteen vertebrae, all of which bear ribs.
All the thirteen ribs (figs. 5 and 6) are well marked, though the
first and the last are very short. It is unlikely that the rib at
the upper end is cervical, or the lower one lumbar in origin in
view of the fact that these regions have their full number of
vertebrae without ribs.
The cause of the scoliosis mentioned previously is shown in
the radiograph. The body of the third thoracic vertebra (fig.
6) is imperfect on the left of the mid-line. It shows ossification
but is only half the size of the right half, and this center of
ossification has remained separate from its fellow on the right
side. The fourth body is slightly tilted up on the left to make
up for the deficiency. The seventh thoracic vertebra on the
left side of its body again exhibits the same deformity, with
lack of fusion of the two centers of ossification in the body, and
in this case the eighth, ninth, tenth and eleventh vertebrae,
lying below it, are all tilted up to compensate for the deformity.
Both defective vertebrae show good neural arches with well
developed ribs articulating with them.
The only points in regard to the skeleton, which are not
brought out by the radiographs, but become evident on dissec-
tion, are that eight costal cartilages articulate with the ster-
num, and that there are only two carpal bones. The carpal
bones are not yet ossified, and so do not show in the radio-
graphs. The proximal one is long and cylindrical, with a con-
vex head proximally articulating with the lower end of the
radius, and a concave facet distally for the other carpal. The
second carpal is an irregular wedge, broad dorsally, narrow ven-
trally, with a proximal convex articulation for the other carpal,
and a concavoconvex facet distally for the metacarpal. It is
impossible to identify either of these bones with any one of the
normal carpal bones, but they resemble the navicular and lesser
multangular more closely than any others.
ANATOMY OF A MONODACTYLOUS FOETUS 395
DISSECTION OF LEFT ARM
MUSCLES
In describing the muscular system in this limb frequent refer-
ence to variations and to comparative anatomy are made,
where it would be tiresome to keep repeating the authority for
such statements. In such eases it is to be considered that Le
Double’s book “‘ Variations du Systeme Musculaire de 1’ Homme?’
has been followed.
Where no comments are offered regarding the variations of
origin or insertion, or additional attachments of any muscle
noted here, it is to be inferred that such departures from normal
have been frequently noted before by others, and are not of
great significance.
As is to be expected, there is little change and abnormality
in the muscles belonging to the upper part of the limb, but great
structural differences become increasingly evident as one proceeds
distally.
MUSCLES FROM AXTAL SKELETON TO SHOULDER GIRDLE AND
HUMERUS
All the following muscles are present and exhibit normal
origins and insertions (figs. 7 to 10).
Sternocleidomastoid.
Subclavius.
Trapezius. Muscle fibers end at level of ninth thoracie vertebra, below this
point there is only a thin aponeurosis.
Rhomboidei, minor et major.
Levator scapulae.
Serratus anterior.
Latissimus dorsi—with an accessory head from the lower angle o£ the scapula.
The two pectoral muscles exhibit some variations from the normal.
Pectoralis major (figs. 7 and 8, P.Ma)
Origin. Normal. ‘
Insertion. Into the outer lip of the bicipital sulcus by a heavy
sheet of tendon. From the deep surface of this tendon two ab-
396 JAMES CRAWFORD WATT
normal accessory heads of origin of the biceps brachii are given
off.
From the lower free edge of the muscle and from the main
tendon there arises an aponeurotic strip which gradually nar-
rows as it passes down the arm and forms a band arching over
the biceps muscle and inserting into the medial epicondyle
and the medial epicondylar ridge of the humerus. This band
is the chondroepitrochlearis muscle, and is not an uncommon
structure, being frequently found in the adult (8 times in 64
subjects, Le Double). It is much more frequent in females than
in males. It is a normal part of the musculature of many of
the lower animals, being known under various other names in
eheiroptera, bears, foxes, Dasypus, Echidna, Batrachia and
Cetacea, and is believed to be homologous with the tensor plicae
alaris of birds (Le Double).
Pectoralis minor (fig. 8, P.M7)
Origin. Statements differ in various textbooks as to the
extent of origin of this muscle, some (e.g., Piersol) say the
third to fifth ribs, others (e.g., Morris) include the second rib
also. In this instance the more extensive origin occurs.
Insertion. The insertion is into the upper surface of the
coracoid process and the outer part of the costocoracoid mem-
brane is so intimately blended with this part of the muscle
that I have debated whether or not to call it a second inser-
tion into the middle third of the clavicle, an attachment which
is occasionally exhibited. The lowest fibers are attached to the
medial surface of the coracobrachialis muscle, an insertion
which has been noted in other cases by Winslow (vide Le
Double).
SHOULDER MUSCLES
The deltoid, supraspinatus, infraspinatus, teres minor, teres
major, and subscapularis are all present, and normal in extent.
ANATOMY OF A MONODACTYLOUS FOETUS 397
BRACHIAL MUSCLES
Coracobrachialis (fig. 8, C)
Origin. From the coracoid process, and capsule of the
shoulder joint, by a common tendon with the short head of the
biceps. The capsular origin is uncommon. The muscle in its
upper part receives fibers from the pectoralis minor as mentioned
above.
Insertion. Into the medial side of the humerus from the
level of the lesser tuberosity almost down to the medial epi-
condyle. What are here present are thus all three divisions of
the muscle, namely, superior, middle and inferior portions.
The superior portion here exhibited is rarely found in man
though normal to some of the lower animals. The coraco-
brachialis superior, when present, inserts into the lesser tuber-
osity, surgical neck, and medial bicipital ridge of the humerus,
also frequently into the capsule of the shoulder joint. It occurs
only very rarely in the Anthropoidea but as a normal structure
in the Quadrumana. It is also present in the elephant, giraffe,
bear, cat, hyena, opossum, Echidna and several other animals.
The coracobrachialis medius is inserted into the middle portion
of the humerus and forms the main mass of the normal human
muscle, the remainder being constituted of the upper part of the
coracobrachialis inferior. The medius is the only portion of the
coracobrachialis present in the aye-aye, the bat, and the sloth,
while it is absent in the kangaroo, otter, and seal.
The coracobrachialis inferior has an extremely variable inser-
tion, extending in different cases from an attachment a couple of
centimeters long on the shaft of the humerus below the medius,
to an insertion on the inner edge of the whole lower half of the
shaft of the bone and the inner epicondyle. In the latter case
it bridges the supracondylar foramen in animals where this is
present and so is perforated by the median nerve and brachial
artery. This muscle is found in the cetacea, the hedgehog, the -
bear, great anteater and others. The inferior portion is much
more developed here than is normal in man, but similar de-
velopment has been frequently found before.
398 JAMES CRAWFORD WATT
Between the upper and middle portions runs the musculo-
cutaneous nerve, but there is no perforation of the lower part
of the muscle by the brachial artery and median nerve, as occurs
when the muscle extends as far as the medial epicondyle of the
humerus. The medial edge of the upper third of the muscle is
connected with the deep surface of the pectoralis major by a
muscular band.
MUSCLES OF THE UPPER ARM
Biceps brachii (figs. 7 and 8, Br)
Origin. The long head arises normally from the supragle-
noid tubercle of the scapula. Its tendon is very thin and
narrow.
The short head is fleshy and heavy, arising by.a broad tendon
from the coracoid process and the capsule of the shoulder joint,
the muscle formed by this head overlapping that of the long
head.
In addition to these two heads two accessory heads are pres-
ent on the lateral side, arising from the deep surface of the
tendon of the pectoralis major and joining the long head at the
level of the bicipital groove. On the lateral surface of this
united bundle comes in a tough short tendon from the deltoid
tubercle and under the long head there is also a distinct bundle
arising from the shaft of the humerus to join the long head.
There are thus seven distinct origins for this muscle. All these
abnormalities have been noted by Le Double though some of them
are extremely rare.
Insertion. The greater part of the muscle passes into a tough
cylindrical tendon passing to the bicipital tubercle on the
radius.
This is a second tendon, however, passing from the super-
ficial and medial aspect of the muscle, as a broad flat band
with diverging crescentic edges. It is attached to the ante-
rior surface of the medial epicondyle of the humerus, and to the
shaft of the radius in front of and beyond the bicipital tubercle.
Between these two points the inferior border of this aponeurosis
ANATOMY OF A MONODACTYLOUS FOETUS 399
presents a free crescentic border under which are visible the other
tendon of the biceps and the tendon of the brachialis muscle.
There is some fusion of the deep fascia of the arm to the muscle
at the beginning of this superficial tendon, which might be
interpreted as a rudimentary semilunar fascia.
The attachment to the humerus must be extremely rare as it
has not been noted by such an authority as Le Double and no
explanation of such an attachment can be drawn from compara-
tive anatomy. The only plausible theory to be entertained is
that this is possibly an extremely well developed semilunar
fascia which has obtained a bony attachment by following the
intermuscular septa to the bones.
The median nerve passes on the superficial surface of this
broad tendon while the brachial artery and vein pass deep to it,
and also behind the round tendon.
The biceps muscle is responsible for the position of partial
supination of the radius, though the hand is pronated. It is
to be remembered that one action of the biceps normally is
rotation of the radius to produce supination, accomplishing this
by a forward pull on the bicipital tubercle which lies posterior
to the long axis of the bone in pronation. In this case the radius
has been rotated until the bicipital tubercle les facing the ante-
rior surface of the humerus. There are no muscles attached
to the radius capable of opposing the biceps in this action and
so the position of supination will be permanently retained.
THE BRACHIALIS MUSCLE
This muscle is divided longitudinally into two portions.
Medial portion (fig. 8, Br.)
Origin. Normal in extent from the lower half of the front
of the shaft of the humerus.
Insertion. The muscle passes down. on the humerus almost
to the articulation with the radius. It is inserted along a
continuous line on the back of the neck and head of the radius,
the joint capsule and the medial epicondyle of the humerus dis-
400 JAMES CRAWFORD WATT
tally and deep to that part of the biceps tendon inserted here,
and deep to the origin of the muscles of the forearm.
This portion of the muscle is supplied by the musculocutaneous
nerve, which is normal, as this portion of the muscle develops
from the ventral musculature of the arm.
The insertion of the brachialis on the radius is to be expected
here, as the ulna is absent, and because it is a frequent abnor-
mality to have accessory insertion on the radius in addition to
its ulnar insertion. Indeed, in addition to the ulnar insertion
in some of the lower animals, such as the horse, the ruminants and
the rodents, a radial attachment is normal and in a few species,
such as the platypus the radial insertion is the only one found.
Lateral portion (figs. 7, 9 and 10, Br.)
This portion is so distinct from the medial portion as to be
practically a separate muscle. It is also divided longitudinally
into two completely separate bundles.
Origin. The two bundles of this muscle arises alongside of
each other, following the lower half of the circumference of the
deltoid tubercle.
Insertion. They pass down the arm as parallel fasciculi and
are inserted on the lateral border of the radius in line with each
other, the most lateral fasciculus being at least a third the dis-
tance down the shaft of the radius. This portion of the muscle
is supplied by the radial nerve and represents the portion of the
muscle developed from the dorsal musculature of the arm and
has, in this instance, separated from the rest of the muscle
formed from the ventral elements. The radial nerve normally
supplies a small portion of the human brachialis muscle on the
lateral side, thus indicating the normal composition of the muscle,
which always has a small portion of the dorsal musculature in-
cluded in it. Le Double cites cases where the brachialis muscle
has been found divided into two distinct heads, as found in this
case, either one of which may be subdivided again. He does not
state the nerve supply, but it is probable the primary separation
is between the dorsal and ventral elements of the muscle.
ANATOMY OF A MONODACTYLOUS FOETUS 401
This lateral portion forms a sharp fold projecting between
the humerus and radius and occupies the deeper portion of the
skin web previously described as binding the arm in flexion at
the elbow. This muscle is very tight and prevents all exten-
sion of the radius on the humerus. It is the muscle so placed
as to most thoroughly prevent this movement, and the part
responsible for this is the lateral portion, due to its insertions
down the shaft of the radius. There is no opposition to this force
as the triceps is not attached to the radius.
Although this muscle occupies only about half the projecting
extent of the skin web here, it is probably the cause of the web,
forcing the skin out in a sharp fold ahead of it. The fold has
developed beyond the extent of the muscle later on.
The lateral portion of the brachialis is responsible for another
displacement of the radius. As its insertion is far down on the
shaft of the radius, and its pull is all to the one side, it has swung
the radius around laterally until the long axis of this bone lies
in a plane parallel instead of perpendicular to the line joining
the two epicondyles of the humerus. This latter relation is not
at first sight apparent, for the forearm appears to be ventral,
not lateral to the upper arm. ‘The reason for this is that the
scapula, carrying the humerus with it is rotated through a
right angle forward and inward on the flattened chest wall.
The scapula has medial and lateral surfaces respectively, instead
of ventral and dorsal. The humerus similarly has medial and
lateral surfaces instead of ventral and dorsal, and the axis at the
lower extremity passing through the epicondyles is not medio-
lateral in direction, but dorsoventral. The forearm thus lies
in a dorsoventral plane although actually rotated laterally
through a right angle.
Triceps brachia (figs. 9 and 10, T,, T., 73)
Origin. The long head is very large and arises from part of
the axillary border of the scapula as well as the infraglenoid
tubercle.
The lateral head arises from the upper third of the posterior
surface of the shaft if the humerus above the groove for the
402 JAMES CRAWFORD WATT
radial nerve, and is quite large. Its border blends with that of
the long head throughout its extent.
The medial head lies on the back of the middle third of the
humerus, below the groove for the radial nerve. It is over-
lapped largely by the long head and blends with the deep surface
and medial border of the latter.
The lower two-thirds of the muscle exhibit a tendon running
lengthwise, at the line of junction of the long and lateral heads.
Towards this tendon fibers converge in the upper part
muscle, and in the lower part they diverge again to their insertion
on the bone.
Insertion. Owing to the absence of the ulna no normal in-
sertion is possible, and the whole lower attachment of this muscle
is transferred to the humerus. ‘The insertion is into the whole
of the lower third of the posterior surface of the shaft of the
humerus and to the back of both epicondyles. The radius re-
celves no attachment whatever from this muscle, so extension
of the forearm is an impossibility. This explains the early
fixation of the forearm in extreme flexion, allowing thus of the
development of the skin web and shortening of the brachialis
muscle to make this deformity a fixed one. Migration of the
attachment of the brachialis down the shaft of the radius is
thus permitted by the permanent flexion of the forearm. In
this position the further the muscle passes down the radius the
shorter it becomes, as its insertion approaches the level of its
origin.
It might be asked why, in absence of the ulna the brachialis
muscle becomes attached extensively to the radius but the tri-
ceps all ends on the humerus. Why does not the triceps also
reach the radius? ‘The difference seems reasonable in view of
the following circumstances, comparative anatomy furnishing
the answer to the problem. The brachialis is attached to the
radius occasionally in man, and as before mentioned, normally
in certain lower animals in addition to its ulnar insertion,
while in a few species the radial insertion is the only one. In the
case of the triceps, insertion on the radius is not normal in the
ANATOMY OF A MONODACTYLOUS FOETUS 403
lower animals even where the ulna is of small importance in the
forearm.
It is to be noted that although the two humeral heads of the
triceps can produce no movement, as they both arise and insert
on the humerus, yet they are both well developed muscle masses.
MUSCLES OF THE FOREARM
There has been great disturbance of the muscles in the fore-
arm, due to the absence of the ulna and reduction of the hand,
but it is still possible to homologise some of them with those of
the normal type. The others however are difficult to define and
the homologies given for them are more in the nature of proba-
bilities than of definite facts. The extensors seem to be more
reduced and more atypical than the flexors.
EXTENSORS
Mostly members of the superficial group are here present as all
of the deep group with one exception are absent. There are four
muscles to consider on this surface.
1. Brachioradialis muscle (figs. 9 and 10, B.)
Origin. High on the lateral epicondylar ridge of the humerus.
Insertion. A very short cylindrical muscle running across
the bend of elbow to insert on the shaft of the radius at about
its middle point, and just to the side of the insertion of the
lateral portion of the brachialis muscle.
This muscle is probably the brachioradialis and its shortening
is not extreme, having been noted in other cases, while in one
of the anthropoids, the gibbon, its insertion is normally high up
on the shaft of the radius.
2. Common superficial extensor mass (figs. 9 and 10, C.E.M.)
Origin. Lower part of lateral epicondylar ridge and outer
surface of lateral epicondyle of the humerus.
404 JAMES CRAWFORD WATT
Insertion. Runs directly parallel to radius and inserts at the
middle of the shaft of that bone, just medial (owing to pronation
apparently lateral) to the brachioradialis.
This muscle probably represents the undifferentiated remainder
of the superficial extensor mass, except the extensor carpi ul-
naris which is separate. It will thus include the extensors carpi
radialis longus and brevis, digitorum communis and digiti quinti
proprius. In some reptilia and amphibia these muscles are in a
common supinato-extensor mass.
Why none of this mass reaches the carpus or digit cannot
be explained, but the fact that none of it does so explains why
the hand is carried in a position of permanent flexion, because
there is a flexor muscle attached to the digit and it is thus
without an opponent to its pull.
3. Supinator (figs. 8 and 10, A.)
Origin. Covered by the common extensor mass it comes from
the anterior surface of the lateral condyle of the humerus.
This represents the superficial or humeral portion only of the
normal human muscle.
Insertion. It courses parallel and deep to the common exten-
sor mass and is inserted into the capsule of the radio-humeral
joint, head, neck and upper third of the shaft of the radius,
right down to the insertion of the common extensor mass.
This muscle, it seems to me, is quite evidently the supinator,
and so is the single representative here of the deep muscles of
the extensor series in the forearm.
Extensor carpi ulnaris (figs. 7, 8, 9 and 10, #.C.U.)
Origin. Below the preceding muscle from the lowest part of
the lateral epicondyle of the humerus. This is the last of the ex-
tensor group and lies in contact with the flexors. It is the
longest of the extensors, being over double the length of any of
the others.
Insertion. By a long slender tendon which is one-third the
length of the muscle, into the middle of the dorsal surface at the
ANATOMY OF A MONODACTYLOUS FOETUS 405
lower extremity of the radius and into the carpus. At the
origin of the long tendon from the belly of the muscle there comes
off also a very short tendon which courses obliquely toward the
flexor surface of the radius and is inserted right alongside of and
practically blended with a part of the flexor digitorum profundus,
about three-quarters of the distance down the bone.
_ This muscle is named the extensor carpi ulnaris because of its
superficial origin from the humerus and its insertion into the
carpus, and because it is the most medial of the extensor muscles
here found, and is in contact with the flexors. All the muscles
inserting into the carpus also show attachment to the lower end
of the radius, this attachment seeming to be due to a spreading
out of the tendon at its insertion, and so I do not think the
radial attachment here offers a serious obstacle to calling the
muscle the extensor carpi ulnaris.
FLEXORS
This group of muscles exhibits members of both the super-
ficial and deep layers and although badly disorganized it still
retains a somewhat closer homology to the normal divisions of
this group than is to be found in the extensors.
SUPERFICIAL GROUP
First layer
1. Flexor carpi radialis (figs. 7 and 8, F.C.R.)
Origin. By a broad fleshy head from the upper part of the
medial epicondyle of the humerus.
Insertion. This muscle is fleshy in the upper half of the fore-
arm and has a long thin tendon coursing through the lower half
to be inserted into the lower end of the radius and into the carpus.
The position of this muscle is along the lateral border of the
radius on its volar surface, although it appears to be dorsal due
to the rotation of the bone.
From its attachments and position it can be quite safely
identified as the flexor carpi radialis muscle.
THE #MERICAN JOURNAL OF ANATOMY, VOL. 22, NO. 3
406 JAMES CRAWFORD WATT
2. Flexor carpi ulnaris (figs. 7 and 8, F.C.U.)
Origin. A broad, flat, fleshy origin from the front of the
medial epicondyle of the humerus and from the surface of the
bone in front of and below this.
Insertion. This muscle is by far the largest of all those yet
described in the forearm. It is fleshy to about two-thirds the
distance down the radius where it narrows into a heavy tendon
which inserts at the lower end of the radius and into the carpus.
Second layer
8. Flexor digitorum sublimis (superficial portion) (fig. 8, F.D.S.)
Origin. Under the origin of the flexor carpi radialis as a
thin flat fleshy muscle which courses obliquely to join one of the
deep muscles arising on the radius, which will be described
later.
This I would homologise with the flexor digitorum sublimis
due to its position as the second layer of muscles from the
medial humeral epicondyle. There is a_ possibility of this
muscle being the humeral portion of the pronator radii teres.
Against this latter view, are the facts that the muscle is entirely
covered by the two carpal flexors, and that it is not inserted
into the shaft of the radius but joins a muscle arising here to be
inserted into the carpus.
DEEP MUSCLES
Third layer
4. Flexor digitorum profundus (figs. 7 and 8, F.D.P.)
Origin. A thick fleshy muscle arising from the lower two-thirds
of the volar aspect of the radius on its lateral (apparently dorsal) _
portion.
Insertion.. This muscle passes as a compact fleshy bundle
as far as the metacarpal region where it condenses into its ten-
don which is single and runs on the volar aspect of the single digit
ANATOMY OF A MONODACTYLOUS FOETUS 407
to be inserted into the terminal phalanx. In its course it passes
under the digital portion of the median nerve which divides on
the digit, allowing the tendon to pass out under it in a manner
similar to that usually shown by the tendons of the flexor digi-
torum sublimis muscle.
The flexor pollicis longus muscle is apparently entirely absent
or much more probably its muscle mass is indistinguishably
fused with that of the flexor digitorum profundus, since the
primitive condition of the deep flexors is a single muscle mass
giving tendons to the thumb and other digits. Man is one of
the very few mammals possessing a flexor pollicis longus muscle
and MeMurrich (’03) has shown that in the other mammals its
absence is not due to a lack of the muscle but to the fact that it
has not differentiated out from the common deep flexor mass
to the digits. It is thus present as the most radial portion of
the flexor digitorum profundus in these forms.
5. Flexor digitorum sublumis (Deep origin) (fig. 8, F'.D.S.)
Origin. From middle third of volar aspect of radius just
medial (apparently ventral) to flexor digitorum profundus.
Joining the proximal part of this muscle is the superficial origin
described above.
Insertion. The common mass so formed passes into a slender
tendon inserted at the lower end of the radius and beginning
of the carpus.
The reason of the failure of the tendon of this muscle to
reach the digit I think must be sought in the failure of the palmar
aponeurosis to which it is attached, to differentiate into a tendon.
MeMurrich (’03) has shown that primitively the sublimis muscle
ends at the wrist inserting into the palmar aponeurosis. Muscles
developed in this aponeurosis later fuse end to end with the
flexor sublimis thus producing its tendons in the mammalia.
The palmar structures included in the sublimis have evidently
failed to form here, leaving the sublimis to end at the wrist.
408 JAMES CRAWFORD WATT
6. Flexor Digitorum Profundus (detached portion) (fig. 8, F. D. P.)
Origin. From the neck of the radius and the shaft of the
bone near this on the medial (apparently ventral) border.
Insertion. This muscle is long and slender. As it is followed
distally into its tendons it divides into a superficial and deep
layer which insert separately. The superficial tendon passes
down to the lower end of the radius and to the carpus. The
short deeper tendon ends almost ixmediately on the shaft of
the radius a short distance above the lower extremity, and is
fused with the short deeper tendon of the extensor carpi ulnaris
already described.
This muscle I interpret as the ulnar part of the flexor digi-
torum profundus, which has differentiated during the muscle
development of the limb and become attached to the nearest
part of the radius. The flexor digitorum sublimis by the exten-
sion of its deep, radial origin, comes between it and the radial
portion of the profundus layer and so may have prevented their
fusion. On the contrary if the lack of fusion was primary
this would allow of the sublimis layer becoming attached down
the radius between the two parts of the profundus. There
is no possibility of this being the flexor pollicis longus as it lies
medial and not lateral to the rest of the flexor digitorum
profundus. .
Fourth layer
7. Pronator quadratus
A thin film of transversely disposed muscle fibers lying over
the lower end of the radius represents the pronator quadratus
muscle. It is very poorly developed and small in extent.
It isto be noted that by means of the muscle in the forearm volun-
tary flexion of the digit is possible but voluntary and active exten-
sion is impossible, as all extensors fail to reach the finger. A singu-
lar and interesting parallel to this case is found ina ease cited by
Schultze (04). In a training school he observed a nineteen
year old lad who had only one digit on each of all four limbs.
Voluntary flexion of these digits was easily accomplished but he
ANATOMY OF A MONODACTYLOUS FOETUS 409
had no power of extension. The probable explanation is that
there was a condition such as present in the case I have dis-
sected. The fact that in both these cases the flexors are evi-
dently better developed than the extensors is significant and
seems to point to certain definite conditions in the muscles
being associated with the deformity.
MUSCLES OF THE HAND (figs. 7 and 8, L.)
Only one muscle is present here. It is a lumbrical, arising in
the metacarpal region from the lateral side of the flexor digi-
torum profundus as this latter muscle passes into its tendon.
The lumbrical passes in a spiral direction distally and laterally
on to the dorsal surface of the digit where it inserts into the
dense fibrous tissue over the phalanges.
NERVES OF THE LEFT ARM
The whole brachial plexus was dissected out as shown in
figure 8 and conformed in all its arrangement and branches to
the typical formation. Therefore it is only necessary to describe
the course and distribution of its main terminal branches.
From the posterior cord
1. Axillary nerve. Normal course and distribution to skin,
deltoid and teres minor muscle, and to shoulder joint (figs. 8 and
ORAL NY:
2. Radial nerve. Runs ventral to the latissimus dorsi tendon,
then winds behind the humerus (figs. 8 and 10, R. N) in the
musculospiral groove, here giving branches to the three heads
of the triceps muscle, and then enters the space between the
triceps and postaxial portion of the brachialis muscle, where it
supplies this part of the brachialis and gives off the dorsal anti-
brachial cutaneous nerve.
A short distance further on the nerve divides into
a. The superficial radial (figs. 9 and 10, S. R. N) which runs a
cutaneous course on the lateral side of the whole length of the
forearm and hand.
410 JAMES CRAWFORD WATT
b. The deep radial nerve, which lies under the three super-
ficial extensor muscles (fig. 10) and on the surface of the supi-
nator which is covered in by the others. The nerve supplies all
these muscles.
From the lateral cord
3. Musculocutaneous nerve. Supplies the coracobrachialis mus-
cle and penetrates it (fig. 8, Mc. N.) between its upper and
middle portions to pass between the biceps and the preaxial por-
tion of the brachialis, supplying both the latter muscles and
ending cutaneously in the forearm.
4. Outer head of the median nerve. The median nerve is
described under the inner cord.
From the inner cord
5. Inner head of the median nerve. Unites with the lateral
head over the axillary artery.
The median nerve (fig. 8, M@. N. ) courses ventral and medial
to the axillary and brachial arteries in the groove medial to
the biceps musele. It enters the forearm deep to the flexor
carpi radialis and superficial head of the flexor digitorum sub-
limis, and in front of the biceps tendon and is accompanied by
the medial vena comes of the brachial artery, while the artery —
and the lateral vein lie under the two biceps tendons. As it
passes the elbow, it gives branches to the flexor carpi radialis,
flexor digitorum sublimis and flexor carpi ulnaris and then
divides into a superficial and a deep branch.
The deep branch evidently is the volar interosseous nerve of
the normal arm, and it supplies the three deep muscles arising
on the shaft of the radius.
The superficial branch of the median nerve (figs. 7 and 8,
M. N.) comes immediately from under cover of the flexor carpi
radialis and courses subcutaneously down the ventral surface of
the lower two-thirds of the forearm and over the carpus. In the
distal third of the forearm it gives off a large cutaneous branch
on the medial side.
ANATOMY OF A MONODACTYLOUS FOETUS 411
At the carpus a strong cutaneous branch is given off on each
side and on the lateral side also a muscular twig to the lumbrical
muscle. The rest of the nerve runs on the ventral surface of
the single digit, finally forking to each side of the digit about the
level of the second phalanx to let the underlying flexor digi-
torum profundus tendon pass through it. This nerve was at
first mistaken for the tendon of the flexor digitorum sublimis
muscle, so typical in appearance was it to this latter structure,
when only its course in the forearm and hand was uncovered.
6. Ulnar nerve. Runs down the arm under the deep fascia
(figs. 7 and 8, U. N.) in company with the basilic vein, pierces
the deep fascia a little above the elbow, and divides into two
branches, a volar and a dorsal, both running subcutaneously
on the medial border of the forearm.
No muscular branches whatever were found on this nerve, its
whole distribution being as a sensory nerve to the forearm.
All other nerves of the brachial plexus which are not specially
described here are normal in their extent and distribution.
VESSELS OF THE ARM
The vessels of the arm were not dissected above the axilla as
it did not seem that any noteworthy changes from the normal
would be likely to occur. No injection was employed as it was
feared that if a vessel wall ruptured structures around the break
might be so stained as to obscure valuable results. Small ves-
sels were thus hard to follow, and arteries to the hand could not
be identified. "
ARTERIES (figs. 8 and 10)
The azillary artery and all its branches were normal in extent
and position.
The brachial artery lay in the groove medial to the biceps
muscle, with the median nerve on its medial side throughout
its course, so that there is no crossing of nerve and artery.
The brachial artery gave origin to numerous muscular branches
and also to three larger branches, the profunda brachii, coursing
412 JAMES CRAWFORD WATT
with the radial nerve through the musculospiral groove, and the
superior and the inferior ulnar collaterals, running medially
alongside the ulnar nerve.
At the elbow the brachial artery (fig. 8) took the astonishing
course of passing behind both the biceps tendons and lying on
the surface of the brachialis muscle. Just beyond this point the
artery bifurcated into two branches which passed down the arm,
one on each side of the flexor digitorum sublimis. The lateral
branch, the radial artery, lay under the flexor carpi radialis
muscle, while the medial, the ulnar artery lay under the flexor
carpi ulnaris. Both arteries became lost in the dissection before
the wrist and hand were reached.
VEINS
Superficial veins (figs. 7 and 9)
The cephalic vein (C. V.) is present here, starting in the hand
and running on the lateral (apparently dorsal) border of the
dorsal surface of the forearm, across the skin web at the elbow,
up the lateral side of the arm, dividing into two channels. These
turn ventrally below the insertion of the deltoid, reuniting here,
then pass between the deltoid and pectoralis major muscles to
terminate deeply in the thoracoacromial vein.
The basilic vein (B. V.) starts also at the wrist, and runs up
on the medial border of the dorsal surface, turning medially to
the ventral surface just above the medial epicondyle of the
humerus. Here it passes under the deep fascia of the arm, run-
ning in the groove medial to the biceps as far up as the axilla
where it unites with the common trunk formed by the union of
the brachial venae comites to form the axillary vein.
Across the back of the elbow a large vein connects the basilic
and cephalic veins transversely.
The median vein (M. V.) courses up the middle of the ventral
surface of the forearm as far as the bend of the elbow where it
divides into two large branches, the median basilic and median
cephalic.
ANATOMY OF A MONODACTYLOUS FOETUS 413
The median cephalic (M.C. V.) runs vertically upward on the
ventral surface of the postaxial part of the brachialis, receiving
as it goes the deep cubital vein from the cubital fossa. The
median cephalic joins the lower half of the cephalic and the com-
mon trunk joins the upper half of the cephalic.
The median basilic runs (VM. B. V.) back over the medial epi-
condyle of the humerus then turns up to join the basilic. It is
double in most of its course.
Deep veins (fig. 8)
The radia and ulnar veins coursing alongside the correspond-
ing arteries unite to form the vena comes lying medial to the
brachial artery, and passing behind the biceps tendons.
Another vein runs back alongside the median nerve in front
of the biceps tendons and half way from the elbow to the axilla
the brachial vein leaves the side of the artery, crosses in front of
the median nerve, and unites with the vein accompanying the
nerve. This common trunk ascends to the axilla and unites
with the basilic to form the axillary.
The azillary vein lies medial and deep to the ulnar nerve and
medial cord of the brachial plexus and receives the usual normal
tributaries.
EMBRYOLOGICAL AND GENERAL CONSIDERATIONS
The first questions that naturally arise in connection with
this case are as to the causative agent and time of production of
the monstrous condition here exhibited. There are several dif-
ferent possibilities to be considered and as the time and the cause
are closely related they will be taken up together.
This deformity may be hereditary and so transmitted in the
germ cells. In the case referred to previously, which was de-
scribed by Schultze (’04), there was only one digit on each hand
and foot and this same identical condition was found in the
mother and the mother’s father, while a brother had mono-
dactylous hands, and other deformities of the feet. It is a well
known fact that monstrosities affecting the limbs show more
414 JAMES CRAWFORD WATT
tendency to be hereditary than many other kinds. Adami (’08)
gives certain good examples of hereditary transmission of such
deformities. There is, however, in the case studied here no
evidence that heredity plays any part in the production of the
abnormality and the cause must be sought for elsewhere.
Again it is possible for a monstrosity to be produced by defi-
ciency in either germ cell, which will produce a deficient ferti-
lized ovum. <A normal fertilized ovum may also be injured and
Conklin (’05) has shown that even in the ovum there is.a differ-
entiation and specific localization of organ forming substances,
one of which could be damaged thus leading to the production’
of abnormal embryos and monstrosities. This has been done
by many workers, only one or two of whom, such as Werber
(15) and Stockard (’09-10) need be mentioned. In this case,
however, damage to either of the germ cells and also to the
fertilized ovum is improbable as there is no history of either of
the parents suffering from venereal disease, alcoholism or drug
habits and neither of them work in noxious surroundings where
poisoning would be possible with lead, arsenic, phosphorus or
other agents.
The period of the production of this deformity is thus excluded
from the germinal stage and must be either in the embryonic or
foetal stages. The foetal stage also can be excluded, for as
pointed out by Ballantyne (’04) in his excellent book on antena-
tal pathology, foetal physiology is, if not identical, at least simi-
lar and parallel to that of the individual after birth, and thus,
foetal pathology is mainly concerned with disease and disordered
metabolism. On the other hand the embryonic period is a
period whose physiology is not that of functional activity of
organs, but of organ formation and differentiation. Pathologi-
cal conditions in the embryonic period, therefore, lead to mal-
formations and so if severe to the production of monsters. The
deformity in this case is thus limited in its production to a period
between the first and seventh weeks of intra uterine life. Dur-
ing this period the limb buds appear and bones and muscles
differentiate in them.
ANATOMY OF A MONODACTYLOUS FOETUS 415
Schwalbe (06) has pointed out that there is a definite termi-
nation period for the production of any deformity. Before the
end of this period practically all deformities of that particular
type must appear, and any produced later than this are to be
regarded in the light of accidental occurrences injuring originally
perfect parts and so simulating abnormalities produced as errors
of development before this termination period. The termina-
tion period in each case marks that special time in which organo-
genesis ceases and functional activity begins in any particular
organ or part and marks the limit in time beyond which a given
deformity rarely if ever has its origin. This reckoning also
places the latest period for the production of the limb deformity
in this case at the seventh or eighth week, when the limb is fully
differentiated and ossification in the limb skeleton begins.
Mall (08) after a critical study of one hundred and sixty-three
pathological embryos, has concluded that most monsters are
produced by the faulty development of normal ova due to ex-
ternal influences, usually a vice of nutrition due to faulty im-
plantation which in turn is generally due to an abnormal condi-
tion of the uterine mucosa. Such a condition for instance would
be a mild, chronic endometritis which would not prevent the
occurrence of a pregnancy but would be enough to cause faulty
development. This might well be the cause here, as there is in
this case a history of two miscarriages previous to the birth of
this monster, without any apparent toxic agent or disease lead-
ing to their production, thus giving presumptive evidence of an
abnormal condition of the uterus, which would cause faulty
implantation and eventual death and expulsion of the products
of conception.
Mall has estimated from statistics from various sources that
in 100,000 pregnancies there are 80,572 normal births, 11,765
abortions of normal embryos, 7048 abortions of abnormal em-
bryos and early monsters, and 615 monsters born at term. In
view of the great prevalence of uterine disorders, superadded to
the unsuitable conditions in which many pregnancies occur, the
pathological development of approximately 7.5 per cent does
not appear unduly high. It will be noted that one monster is
416 JAMES CRAWFORD WATT
born at term in approximately every one hundred and thirty
births.
For a full discussion of the many teratological theories the
reader is referred to Ballantyne’s text book on antenatal pa-
thology. It is sufficient to mention briefly any other likely causes
of the present deformity. Maternal impressions still possess
many firm believers, but. I think as a cause their utter power-
lessness in this case is clearly demonstrated. The impressions
were received later in pregnancy, the deformity, as shown above,
must have been established very early, so the relation of the two
as cause and effect was absolutely impossible. (See page 387).
Foetal diseases do not appear as a rational cause of this de-
formed condition and neither do amniotic diseases. Amniotic
bands and adhesions have been ascribed almost universal tera-
tological influences by devotees of this theory, and when they
could not be demonstrated, their previous existence and later
disappearance has been postulated. There is no cicatrix or
other evidence of any band connected to the extremities here,
and the symmetry of the deformity argues against its produc-
tion thus. The accompanying defects in the vertebral column
are evidently not due to such bands.
There*is one cause in the production of monstrosities and of
pathological embryos that it seems to me is perhaps a fruitful
one and which I have not found mentioned by other authors.
I refer to attempts in the production of criminal abortion, which
as every physician knows, are so prevalent amongst the women
of this age. These attempts are not always immediately suc-
cessful but sometimes the pregnancy is terminated by the death
of the injured child at some later date and in some cases preg-
nancy goes:on to full term in spite of the injury. Is it not ex-
tremely possible that in these instances where the child continues
to live for some time after the attempt to destroy it, that it
should exhibit some monstrous condition, especially when the
attempt is made in the first two months? Both the use of
mechanical means and of drugs would result in these pathological
conditions, the instrument by direct injury to the child or to
the amnion, the drugs by affecting the implantation in the
ANATOMY OF A MONODACTYLOUS FOETUS 417
uterus, and so being one cause of the condition to which Mall
ascribes most pathological embryos. To show that attempts at.
abortion form a cause not to be neglected in this regard I quote
from the Secretary of the Indiana State Board of Health, Dr.
J. N. Hurty (17) who says ‘“‘It has been estimated that about
one-third of pregnancies end in induced abortions, that at least
200,000 volitional abortions occur every year in the United
States and that not less than 12,000 women die annually from
the direct effects thereof.’’ (This is quoted from another article
as I regret I have been unable to obtain the journal with Dr.
Hurty’s original article in it.) Surely the arguments I have
used above are sound in view of such conditions as Hurty states
to exist and attempted abortions which are not immediately
successful ought to be ranked amongst the causes of pathological
embryos and monstrosities.
Some of the abnormal conditions found in this foetus can be
correlated with interesting embryological stages of growth which
it seems to me throw considerable light on what are otherwise
obscure isolated facts. Statements as to normal skeletal and
muscular development are taken from the accounts by Bardeen
and Lewis in Keibel and: Mall’s Human Embryology. (10).
In the early development of the vertebra, as the scleroblas-
tema becomes chondrified, this process in the bodies of the verte-
brae is brought about by two centers, one on each side of the
‘notochord. At first there is no fusion of these two centers of
chondrification dorsally or ventrally around the notochord, as
there is present in the mid line a membranous perichordal sep-
tum (Keibel and Mall). Normally this septum is soon broken
through both dorsally and ventrally and the notochord is com-
pletely surrounded by cartilage by about the fifth or sixth week.
Ossification then occurs from a center which is usually single,
but may divide or even arise paired.
The early presence of the perichordal septum appears signifi-
cant in view of the fact that in this foetus are found two verte-
brae with divided bodies, each half growing independently, and
one-half growing less rapidly than normal. This septum was
present at the period of embryonic life when that vice of develop-
418 JAMES CRAWFORD WATT
ment occurred which produced the monstrosity of the limbs. Is
it not very probable that the chondrification process in these two
abnormal vertebrae was hindered so that the perichordal sep-
tum was not broken down, but remained intact, thus producing
a vertebra with a divided body?
Ossification as mentioned above tends to occur in the body
from one center, which may be divided. Under such condi-
tions, with the perichordal septum intact it is possible that more
of the ossifying center should be in one half than the other, thus
accounting for the unequal rate of growth in the two separated
halves.
There are some other points of interest in the vertebral col-
umn. The lateral masses of the sacral vertebrae ossify as fol-
lows: the first at the fifth month of intrauterine life, the second
at the sixth month, the third at the seventh month, the fourth
and fifth after birth about three months. In this foetus, the
age was given as seven months and the third lateral mass center
is Just appearing, thus showing a normal rate of growth.
The first coceygeal vertebra in this foetus has a center of ossi-
fication in its body, while normally it appears in the first year
after birth, so in this region there is an actual acceleration of .
ossification, in direct opposition to the retardation or suppression
shown in the abnormal portions of the skeleton.
The core of the limbs at the third week is filled with vascular
mesenchyme which at the fourth week becomes a scleroblas- ~
temal condensation which then becomes successively chondrified
and ossified. The primary failure of the digits and ulna of this
foetus can thus be placed as far back at least as the fourth or
fifth week of development, at the time when the differentiation
of the skeletal parts should have occurred. This would corre-
spond with the time of production of the defect in the abnormal
vertebrae. These facts would seem to indicate that at this par-
ticular period was exerted the strongest and most active influ-
ence of the agent producing the deformities.
‘Absence of the ulna is a much rarer condition in the forearm
than absence of the radius. Kiimmel (’95) has collected a series
of cases of defect in the bones of the forearm. Unfortunately
ANATOMY OF A MONODACTYLOUS FOETUS 419
I could not secure the journal containing his original article but
Ballantyne (’04) in his text book and Schenk (’07) in an article
on a case of defect of the ulna agree in their accounts of Kiim-
mel’s cases which can be taken as correct. He found 80 in-
stances of defect in the bones of the forearm of which 67 were
of the radius, 13 of the ulna. In the case of the ulna it was
defective in 5, totally absent in 8 instances. In some of these
cases there was associated absence of the ulnar side of the carpus
and one or more fingers on the ulnar side of the hand.
The muscles of the limb definitely appear first proximally and
differentiation proceeds distally. It might be expected that the
muscles of the shoulder girdle and upper arm, being the first to
appear after the skeletal deformities were produced, might show
some anomalies. They do exhibit anomalies, but peculiarly
not anomalies of defect, but of excess, such as supernumary
heads and increased insertions. Of course, in the forearm and
hand grave defects are associated with the loss of the skeletal
structures.
The question naturally arises as to whether the muscle
anomalies are a consequence of the skeletal defects or were inde-
pendently produced by the same vice of development or nutri-
tion to which the absence of the bones is due. In this connec-
tion it is to be noted that the suppression of muscles in the fore-
arm is not confined to the ulnar border of the arm but affects
also the radial side, so that more than mere absence of the skele-
ton underlies the anomalies. This can be proved by the fact
that muscle is independent and self-differentiating. Muscles
develop independently of functional activity as shown here by
the two humeral heads of the triceps, inserted also on the hu-
merus, incapable of movement, yet well developed. Harrison
(04) also proved that muscles develop independently of the
nervous system, for he removed the spinal cord in early frog
embryos, before the muscles had differentiated or received any
nervous connection and yet the normal process of muscle de-
velopment and grouping occurred. This power of self-differ-
entiation goes right back to the ovum where Conklin (’05) has
420 JAMES CRAWFORD WATT
demonstrated the presence of a myoplasm or muscle forming
substance.
In the forearm the extensor and supinator group differentiate
before the flexor and pronator set. As the muscle formation
follows closely upon the definition of the skeleton, if the growth
suppressing influence which acted on the skeleton lasted long
enough to influence the muscles it 1s to be expected that the exten-
sor group would exhibit the greatest amount of damage. Such
is actually the case. Only four extensor muscles are present as
against seven flexors and pronators plus one palmar muscle.
Only one extensor muscle reaches as far as the lower end of the
radius, nearly all the flexors reach that level. No extensor ten-
don reaches the digit, a flexor tendon passes right out to the
terminal phalanx, in addition to bearing a lumbrical muscle to
the digit. It is to be noted that in the members of the extensor
group here present the muscle masses are of about normal pro-
portion, covering half of the length of the radius but in only one
case is a long tendon developed, the other muscles inserting at
once on the middle of the shaft of the radius. This failure of
the long tendons to differentiate out after the appearance of
these muscles is a further example of the greater suppression of
growth in this region. Grafenberg (’11) describes the muscula-
ture in a case of absence of the radius and the thumb. Here
the radial musculature is present as a common mass high up in
the forearm, possessing no tendons, and so appearing very much
like the extensor muscles I have described. The other muscles
both flexors and extensors, in Grifenberg’s case are present and
normal in extent.
Regarding the muscle that I have called the common super-
ficial extensor mass, as separation into separate portions begins
at the carpus after the appearance of the tendons, it is not pos-
sible here to have such a division into its component muscles,
because its tendon is entirely absent.
Absence of the thumb is not enough to cause disappearance of
the abductor pollicis longus and extensor pollicis brevis, the
radial members of the deep extensors, for there is still oppor-
tunity for the muscles to develop over the radius. The triceps
ANATOMY OF A MONODACTYLOUS FOETUS 421
did not fail when the ulna disappeared. The same is true of
the ulnar members of this group, the extensor pollicis longus,
and extensor indicis proprius. All this group have been obliter-
ated by a specific suppressing agent during myogenesis.
In the flexor muscles it seems strange that the pronator teres
is not present when so many of the other muscles are. Its com-
plete absence has never been noted as an anomaly although its
coronoid head has often been lacking. In lower vertebrates this
muscle is a part of a common muscular layer known as the pro-
natoflexor mass. In this foetus it may be present in the super-
ficial layer, included with the mass of the flexor carpi radialis,
having failed to obtain an insertion at the usual level on the
radius.
It is interesting to note that in this foetus a definite tendency
in one direction is shown by all muscles, which are properly
developed and which show anomalies. This tendency, for in-
stance is shown by all the muscles on the front of the upper arm
and is a regression or atavistic change, the anomalies resembling
normal muscles of the lower animals. Changes due wholly to
loss of normal skeletal parts lead to anomalous attachments
which of course cannot be properly included in this class as they
are in the nature of monstrosities.
The question naturally arises as to what single digit it is that
has persisted in this hand, and also what carpal bones are present.
It may be taken as a plausible working hypothesis that with
loss of the ulna would be associated loss of the ulnar side of the
carpus, with the fourth and fifth digits.
This hypothesis is supported by the fact that the main cu-
taneous digital nerves ventrally are two strong branches from
the median while dorsally the radial reaches the base of the
digit. The ulnar nerve has no digital distribution, and as it
normally goes to the fourth and fifth digits while the median and
radial supply the other three, the digit here present certainly
ought to be one of the three on the radial side of the hand.
This would leave three digits still to decide between. This
number can be further reduced to two as the thumb is certainly
absent, for the persistent digit has a metacarpal and three pha-
THE AMERICAN JOURNAL OF ANATOMY, VOL. 22, NO. 3
422 JAMES CRAWFORD WATT
langes, and a lumbrical muscle is also found attached to it. The
median nerve normally supplies the lumbrical muscle to the
second and third digits, the ulnar those to the fourth and fifth.
The single lumbrical here present is supplied by the median, a
further proof that the digit is the second or third.
The digit is thus either the index or middle finger, but to
decide upon which of these two it is, is much more difficult as
there is nothing in the disposition of the muscles to help solve
the problem. The distribution of the cutaneous branches of
the median nerve seem to offer the only key to the solution. In
text figures C and D is given side by side the cutaneous distri-
bution of the median nerve in this foetus and in the normal
hand. As the cutaneous distribution of the median is wholly
digital it is assumed that branches found from the trunk of the
median running into the hand were intended for those digits
which did not appear. By checking these off against the
branches in the normal hand it is found that the digit here pres-
ent ought to be the index finger.
There is a palmar cutaneous branch from the median arising
in the lower half of the forearm and ending in the palm. It is
not to be mistaken here for one of the digital nerves, these latter
arising in the palm. ‘There are three such nerves, only the
middle one passing out on the digit, where it forks to supply
each border, while the flexor profundus tendon passes on under
it. The other two nerves end at the base of the digit on its
medial and lateral borders. To save a long description the
reader is referred to the figure explaining the distribution of
these nerves. Here at a glance it can be seen that the part of
the nerve found on the digit in this foetus, is the portion to the
index finger from the first and second common volar digital
branches.. From this distribution it seems fairly definite that
the sole remaining digit on this hand is the index finger.
On the arm which was not dissected it will be remembered
that in addition to the single finger carried at the end of the
limb there was a well developed digit found on the medial side
of the elbow. Radiographs showed this to contain a metacarpal
and three phalanges. Of course, this digit can be logically as-
ANATOMY OF A MONODACTYLOUS FOETUS 423
sumed to be one of the ulnar members which has differentiated
in spite of the total suppression of the ulna and part of the car-
pus. Its appearance at the elbow and not the carpal region
lends color to the view that the ulnar anlage of the limb skele-
ton never appeared at all even in the early mesenchyme, so that
Palmar
cutaneous N.
D
)
j
i
Median Nerve-
Third common
volar digital N.
TAG GaLnRte.—
First: common P
volar digital N.
a
:
Second common
volar digital
om
=== oo
Si
Tendon of
Flexor digitory \
profundvs
F lexor digitorum
sublimis
Tendon of
Flexor digitorum
profund Us
IV Digit Il
Ul
Text fig. C Outline of the cutaneous distribution of the median nerve in the
normal human hand.
Text fig. D Outline of the cutaneous distribution of the median nerve in the
left hand of this monodactylous foetus.
LT he part of the nerve shown in solid black in the two figures, is reckoned as
identical in the two hands, and is used to determine what single digit is present
in the foetus.
the primary reason for nonappearance of the ulna was not a
lack of chondrification and ossification.
There is another view in regard to this digit, and that is that
the digit is really the representative of all five normal ones,
being the result of development of the original undivided digital
424 JAMES CRAWFORD WATT
anlage in the earliest stage of the limb skeleton as the distal end
of the condensed scleroblastemal core.
In view of the facts already expounded it seems to me that
this latter view is not likely to be correct. The ulnar nerve
ought to have a digital cutaneous distribution if the ulnar fingers
of the hand are represented in this common finger, but the ulnar
does not pass out on the digit, thus supplying one argument
against this hypothesis.
The presence of one digit at the elbow joint on the right arm
postulates the separation of one digital rudiment from the com-
mon mass. If it separated then clearly the tendency to division
of the skeleton of the hand into rays was present and it is Just
as tenable to suppose that the five-rayed condition of the hand
was provided for, but growth suppressed in four, as it is to sup-
pose all five rays of one hand and four in the other to be in-
cluded in a common mass.
The fingers here present, both in the hand and at the elbow,
as will be seen from the table of measurements, are normal in
size for a single digit. The development of an undivided com-
mon digital mass might be expected to produce a condition of
macrodactyly, which is not found here. Considering all the
facts, the view that the digit as found on the hand here repre-
sents only one of the five of the normal hand seems to be the
correct view in this case.
What carpals are present is not capable of definite answer.
There are only two present, a proximal one articulating with the
radius and bearing beyond it a distal one which carries the digit.
These two in their shape as previously described resemble the
navicular and lesser multangular more than any of the other
earpals. Their absolute identification, however, as these two,
is hardly to be warranted from these facts alone. If it be true
that these are the two carpals present it adds another proof for
the digit being the index finger as these two particular carpals
are in the direct line of the radius and the second digit.
In the mechanism of the production of the deformity in the
limb several different conditions have to be considered. First,
in the early limb bud the ulnar segments may not have been
ANATOMY OF A MONODACTYLOUS FOETUS 425
carried out in the distal part of the evagination from the trunk
of the body, being drawn out later only in the proximal part of
the limb, so that a complete upper arm is formed but only the
radial half of the rest of the limb. Secondly, these segments
may have been drawn out, the limb bud being normal, but fur-
ther differentiation not occurring, so that what is seen in the
limb represents a fused radius and ulna in the forearm, fused
carpals and digits in the hand. The arguments against the
digit really representing all five have already been reviewed,
and against the view of the ulna being included in the forearm
is the absolutely typical shape and size of the radius, the dis-
tribution of nerves and muscles, and the appearance on the
right arm of a digit at the elbow, as if this point represented the
distal end of the ulnar portion of the arm. Thirdly, the limb
bud again may have been normal, without fusion of the radial
and ulnar anlagen in the skeleton, only the radial half going on
with its development, the ulnar half failing entirely, except for
the digit at the right elbow. The presence of this digit lends
color to this third view.
DIAPHRAGMATIC HERNIA
After the rest of this paper was written, out of curiosity
aroused by the flatness of the abdomen, I opened the body
cavity to examine the viscera, and was surprised to discover a
diaphragmatic hernia with a large proportion of the abdominal
viscera situated in the left pleural cavity. The right half of the
diaphragm was intact and perfect, but the left half was almost
entirely absent. The sternal and vertebral regions were present
and joined in the central tendon, forming a free edge to the dia-
phragm in the midsagittal plane. The left costal origin was
indicated in front by a muscular ridge 2 to 3 mm. high following
the costal margin as far back as the axillary line and the whole
of the left half of the diaphragm except this narrow peripheral
band was absent, leaving a wide open communication between
the pleural and ‘peritoneal cavities. The left mediastinal pleura
passed over the medial free edge of the opening to become dia-
phragmatic peritoneum under the right half of the diaphragm,
426 JAMES CRAWFORD WATT
the costal pleura passed on down as parietal peritoneum on the
abdominal wall.
The hernia is thus of the variety known as hernia diaphrag-
matica spuria. Cases of hernia diaphragmatica vera have a
hernial sae formed of diaphragmatic peritoneum and_ pleura
invaginated into the pleural sac, so that the abdominal viscera
are not in reality in the pleural sac. In this case however, there
is no hernial sac, but a complete hole through the diaphragm
and its coverings. The genesis of this condition I would inter-
pret as a persistence of the embryonic pleuroperitoneal passage,
the original communication between the pleural and peritoneal
cavities, which has not been shut off, due to the failure of the
septum transversum to grow back on this side. The left side
normally closes a little later than the right (Keibel and Mall,
10) and this may be one factor in the greater prevalence of
hernias on the left side.
This defect in the diaphragm must have had its origin during
the development of the structure, and so occurred between the
fourth and eighth weeks of intrauterine life, probably, on account
of its size, in the first half of this period, say the fifth week,
which synchronises exactly with the production of the defects
in the limbs and vertebral column.
The heart has been pushed over entirely to the right side by
the other viscera, but apart from its position is quite normal.
The left lung shows two lobes, but is extremely small and flat-
tened against the mediastinal wall just above the heart. The
abdominal viscera are all fairly normal in relation to each other
and seem to have been rotated en masse up and over toward
the right. The left lobe of the liver is thus vertical, and against
the mediastinal wall. The oesophagus comes from behind the
upper end of the heart into the stomach and the latter is vertical,
the pylorus being in the abdomen. The duodenum lies over the
vertebral column and the small intestine runs from it into the
pleural cavity, successive coils being piled continuously above
the previous loops up to the apex of the cavity, where the
gut is reflected down medially. Opposite the lung occurs the
junction with the caecum and appendix. The colon descends
ANATOMY -OF A. MONODACTYLOUS FOETUS 427
as far as the duodenum, then turns suddenly back on itself and
ascends in the great omentum against the stomach to its upper
end, then turns sharply down on the body wall, loses its mesen-
tery and runs on the wall to the brim of the pelvis, where it
turns suddenly into a large loop extending up again as high as
the liver before turning to come down into the rectum.
Diaphragmatic hernia seems to be a fairly common condition
as Ballantyne (’04) collected one hundred cases in the literature
from 1888 to 1900. It is a peculiar coincidence, that in one of
those cases, just as in this present one, there was also absence
of the ulna. This is all the more interesting because Ballan-
tyne states that associated malformations occur less frequently
in conjunction with ulnar defects than with defects of other
bones in the limbs.
In bringing this study to a close I wish to very cordially thank
Prof. J. Playfair MeMurrich for providing the material for the
work and also for his valuable, kindly criticism of this paper
during its preparation.
May Ist, 1917.
428 JAMES CRAWFORD WATT
BIBLIOGRAPHY
Apami, J. G. 1908 The Principles of Pathology, vol. 1. Lea and Febiger,
Philadelphia and New York, 1908.
BALLANTYNE, J. W. 1904 Manual of Antenatal Pathology and Hygiene, vol.
1. The Foetus; vol. 2. The Embryo. Green, Edinburgh, 1904.
Baraso 1900 Eine Missbildung. Offic. Protok. der Niirnberger Med. Ges.
und Polikl. Munch. Med. Wochensch, 1900, S. 713.
Conxkuin, E. G. 1905 Organ-forming substances in the eggs of Ascidians.
Biological Bulletin, vol. 8, p. 205.
GRAFENBERG, EF. 1911 Die Muskulatur in Extremitaitenmissbildungen Anat.
Hefte, Bd. 42, S. 195-250.
Harrison, R. G. 1904 An experimental study of the relation of the nervous
system to the developing musculature in the embryo of the pig. Am.
Jour. Anat., vol. 3.
Hurry, J. N. 1917 Indianapolis Medical Journal, January.
KEIBEL, F., anp Mau, F. P. 1910 Manual of Human Embryology, vols. I and
II. Lippineott, Philadelphia and London, 1910.
Kinet, E. 1895 Die Missbildungen der Extremitiiten durch Defect, Ver-
wachsung und Uberzahl]. Biblioth. Med., Abt. E., Heft 3.
Le Dovusuir, A. F. 1897 Traité des Variations du Systéme Musculaire de
lHomme. Schleicher, Paris 1897.
Mau, F.S. 1908 A study of the causes underlying the origin of human mon-
sters. Jour. Morph., vol. 19.
McMoraicu, J. P. 1903 The phylogeny of the forearm flexors. Am. Jour.
Anat., vol. 2.
1915 The development of the Human Body, Fifth Edition. Blakiston,
Philadelphia.
Scoenk, E. 1907 Ueber zwei Fille typischer Extremititen Missbildungen
(Ulnadefekt, Fibuladefekt). Frankfurter Zeitsch. fur Pathol., Bd. 1,
H. 3 und 4, 8. 544-62.
Scuuttze, E. 1904 Familiire Symmetrische Monodactylie. Neurol. Central-
blatt, S. 704.
Scuwase, E. 1906 Ueber Extremitaitenmissbildungen (Spalthand, Spaltfuss,
Syndaktylie, Adactylie, Polydactylie.) Munch. Med. Wochensch.,
S. 493.
1906 Die Morphology der Missbildungen des Menschen und der
Tiere, T. 1 und 2. Fischer, Jena, 1906-7.
Srockarp, C. R. 1909 The development of artificially produced Cyclopean
fish—“‘The Magnesium Embryo.”’ Jour. Exp. Zo6l., vol. 6.
1910 The influence of alcohol and other anaesthetics on embryonic
development. Am. Jour. Anat., vol. 10.
Werser, E. I. 1915 Is defective and monstrous development due to parental
metabolic toxaemia. Abstract in Anat. Rec., vol. 9, p. 133.
1915 Experimental studies aiming at the control of defective and
monstrous development. A survey of recorded monstrosities with
special attention to the ophthalmic defects. Anat. Rec., vol. 9, p.
529.
Standard recent textbooks of Human Anatomy.
ANATOMY OF A MONODACTYLOUS FOETUS
429
ABBREVIATIONS
A, supinator muscle
A.A., axillary artery
Ac, acromion process
A.N., axillary nerve
A.T.N., lateral and medial anterior
thoracic nerves
A.V., axillary vein
B, braghioradialis muscle
B.A., brachial artery
Bi, biceps muscle
Br, brachialis muscle
B.V., basilic vein
C, coracobrachialis muscle
C.E.M., common superficial extensor
muscle mass
Ch, chondroepitrochlearis muscle
Cl, clavicle
Cu.V., cubital vein
C.V., cephalic vein
D, deltoid muscle
Dx, cut edge of deltoid muscle
E, lateral epicondyle of humerus
E.C.U., extensor carpi ulnaris muscle
F.C.R., flexor carpi radialis muscle
F.C.U., flexor carpi ulnaris muscle
F.D.P., flexor digitorum profundus
muscle
F.D.S., flexor digitorum — sublimis
muscle
H, head of humerus
H.R., head of radius
I., medial epicondyle of humerus
I.B.N., intercostobrachial nerve
Inf., infraspinatus muscle
L., lumbrical muscle
L.C., lateral cord of brachial plexus
L.D., \atissimus dorsi muscle
L.S., levator scapulae muscle
L.T.N., lateral thoracic nerve
M.A.C.N., medial
taneous nerve
M.B.C.N., medial brachial cutaneous
nerve
M.B.V., median basilic vein
M.C., medial cord of brachial plexus
Mc.N., musculocutaneous nerve
M.C.V., median cephalic vein
M.N., median nerve
M.V., median vein
P.A., profunda brachii artery
P.C., posterior cord of brachial plexus
P.C.A., posterior humeral circumflex
artery
P.Ma., pectoralis major muscle
P.Mi., pectoralis minor muscle
f., rib
Rh, rhomboid muscles
R.N., radial nerve
S.A., serratus anterior muscle
S.C.M., sternocleidomastoid muscle
S.N., supraseapular nerve
Sp., spine of scapula
S.P.J., serratus posterior inferior
muscle
antibrachial cu-
Spl, splenius cervicis et capitis muscle
S.R.N., superficial radial nerve
Sup, supraspinatus muscle
T,, long head of triceps muscle
T», lateral head of triceps muscle
T;, medial head of triceps muscle
T.Ma, teres major muscle
T.Mi, teres minor muscle
Tr, trapezius muscle
Trx, cut edge of trapezius muscle
U.N., ulnar nerve
X, depression in back over defective
vertebrae
Bm CO he
PLATE 1
EXPLANATION OF FIGURES
Deformed foetus seen from in front.
Deformed foetus seen from left side.
Left arm, viewed laterally, showing monodactyly and webbed elbow.
Right arm, viewed ventromedially, showing monodactylous hand and extra
digit located at elbow.
430
ANATOMY OF A MONODACTYLOUS FOETUS PLATE 1
JAMES CRAWFORD WATT
PLATE 2
EXPLANATION OF FIGURES
5 Radiograph of foetus from right side. Thirteen thoracic vertebrae and
ribs are shown.
ANATOMY OF A MONODACTYLOUS FOETUS PLATE 2
JAMES CRAWFORD WATT
Cervical
Vertebra lv
Cervical vy ‘\
Vertebra vi
Thoracic
Vertebra !. >
Scapvla.
>
Oa
2
Thoracic
VertebraXl
Pater : Clavicle
Verte bra ¥
Redius
Lumbar
Mertebra vy
Sacral Ee.
Vertebra I=
13U Rabe Humerus
Tlium
Sacral
Femur
Vertebra
Ischium
Pubis
Tibia
Talus Fibula
Calcaneus
Proximal Phalanges
Distal Phalanges
Metacarpals
PLATE 3
EXPLANATION OF FIGURES
6 Radiograph of foetus from ventral surface to show thirteen thoracic verte-
brae and ribs. Two defective vertebrae are seen in the thoracic region.
434
ANATOMY OF A MONODACTYLOUS FOETUS PLATE 3
JAMES CRAWFORD WATT
Cervical
Vertebra I.
Thoracie
Vertebra }.
\Vertebra
with body
divided.
\ Verte bra
A lwith body
divided.
p Lumbar
Vertebra I.
Sacral
Vertebra I
ateral mass
of Sacral
Vertebrs.
Ceccygea!}
Vaere ebrea tT
ia |
co 0
PLATE 4
EXPLANATION OF FIGURES
Superficial dissection of the ventral surface of the left arm.
Deep dissection of the ventral surface of the left arm.
Superficial dissection of the dorsal surface of the left arm.
Deep dissection of the dorsal surface of the left arm.
436
ANATOMY OF A MONODACTYLOUS FOETUS PLATE 4
JAMES CRAWFORD WATT
437
THE AMERICAN JOURNAL OF ANATOMY, VOL. 22, NO. 3
AUTHOR’S ABSTRACT OF THIS PAPER ISSUED
BY THE BIBLIOGRAPHIC SERVICE OCTOBER 6.
THE NORMAL SHAPE OF THE MAMMALIAN RED
BLOOD CORPUSCLE
LESLIE B. AREY
From the Anatomical Laboratory of the Northwestern University Medical School!
ONE FIGURE
CONTENTS
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A. INTRODUCTION
It has been a classical teaching that the normal shape of the
mammalian red blood corpuscle is that of a biconcave disc.
Within the last decade and a half, however, a few workers have
vigorously assailed this view and have asserted that intravitally
the erythroplastid is concavo-convex, 1.e., has the form of a cup
or bell, and that the biconcave disc first appears after blood is
drawn from the vessels. According to this latter view, the cup
is the normal form, the disc the derived one.
That under certain conditions cup-shaped corpuscles can
actually be found in ordinary preparations of drawn blood, in
fixed tissues, and even in circulating blood no one will deny;
1 Contribution No. 49; May 25, 1917.
439
440 LESLIE’ B. AREY
such forms have been seen and described since the days of the
pioneer microscopists. The issue, therefore, hinges entirely on
the determination of what is the normal intravital condition,
and what the modification or artefact.
Waener (’33, p. 4) was the first to appreciate and definitely
formulate this, our present contention: ‘‘Ob die menschlichen
Blutkérnehen auf beiden Flaichen platt oder konvex oder gar
konkav sind, oder konvex-konkav, wie wohl behauptet worden
ist lisst sich schwer ausmitteln :
Evidence as to the shape of the ecythroplastia has been de-
rived from three sources: (1) drawn blood; (2) circulating blood;
(3) fixed tissues or smears. The results obtained previously in
each of these fields will first be considered separately.
B. HISTORICAL
1. Results from drawn blood
The desultory microscopical observations of Leeuwenhoek
(1719) included an examination of mammalian blood, he ap-
parently being the first to observe this tissue attentively. Blood
drawn from the finger was mixed with an aqueous decoction of
pareira brava, the resulting dilution facilitating its study.
Han IEEE, fie description (epistola 44, p. 422) is as follows:
: most of the corpuscles hare a certain concavity
or sinus receding into them, as if we have a vesicle full of water
and by pressure of the finger should indent the middle of the
vesicle as a pit or depression.”
Muys (1738), Fontana (1787), and Dujardin (’42) essentially
substantiated Leeuwenhoek’s conclusion. It is evident, how-
ever, that the uncontrolled type of observation recorded by
Leeuwenhoek retains an historical interest only, for the action
of water in altering the shape of these corpuscles is a matter of
common knowledge, dating back to the time of Muys (1751).
Schultze (65) was the first to record the occurrence of some
spherical red corpuscles in drawn blood. Later, in 1877, Litten
examined the blood of severely anemic individuals and found
cup-like corpuscles which he described as ‘pessary’ forms; these
SHAPE OF MAMMALIAN RED BLOOD CORPUSCLE 441
he believed existed also .in limited numbers in normal blood.
Quincke (’77) and Grawitz (’99) saw cup shapes among the
poikilocytosed corpuscles of severe anemias; Grawitz (’02)
further recorded having observed a tendency toward crenation
in fever patients.
At about this time Ranvier (’75) demonstrated that increased
temperature produced cups or spheres according to the degree
of elevation. This heating effect has keen emphasized by v.
Ebner (’02), Fuchs (’03), Albrecht (04), and Zoth (cited by
Lohner 710). Here might be mentioned the probably erroneous
contention of Hamburger (’02) that a correlation exists between
the oxygen-carbon dioxide content of the blood and the shape
of the corpuscles; in blood rich in oxygen (carotid artery) discs
were described, whereas the corpuscles of blood having a high
carbon dioxide content (jugular vein) were believed to be cup-
shaped.
During the two hundred years in which the foregoing data as
to the existence of cups were being collected, observations of
another sort were recorded.
de Senac (1749) referred to red corpuscles as having a lentic-
‘ular shape, ‘‘plus approchantes d’une sphére appatie au veri-
tablement lenticulaires.”’
The corpuscles were studied with considerable care by Hewson
(1777) who says (p. 214): ‘‘These particles of the blood, improp-
erly called globules, are in reality flat bodies . . . .” He
diluted the blood of animals with blood serum? and records his
observations (p. 215): “* . . .. . these particles of ‘blood
were as flat as a guinea.”
J. Miiller (’32) stated that the corpuscles in side view resemble
coins; Schultz (36), Prevost and Dumas (’21) and other con-
temporaneous writers made essentially the same comparison.
In 1838 Wagner decided in favor of the normality of the
biconcave disc (cf. p.440). Henle (’41), the atlases of Funke (53)
and Ecker (’51—’59), and many more recent works figure the
familiar biconcave shape.
2 Although Muys (1751) mentioned the difference between: the action of serum
and water, it was not until 1813 that Young proved water,not actually to dis-
solve the corpuscles.
442 LESLIE B. AREY
The effect of water, first noted by Muys (1751), was studied
by Malassez (’96) who showed that shapes intermediate between
the dise and sphere are obtainable in examining media of dif-
ferent concentrations and that hypertonic solutions induce crena-
tion. Crenation does not necessitate permanent injury, for a
return to weaker solutions allows recovery (Heinz ’90; Weiden-
reich ’02).
Previous to the year 1902 observations on the shape of the
red blood corpuscle for the most part had been of a casual na-
ture. That the cup might be the true normal form was not
considered seriously. Standard texts and atlases continued to
describe the classical disc, although in a few cases (e.g., the
‘atlas of Brass, ’97) cups were also figured.
The renewal of interest in the cup form resulted from a series
of detailed investigations by Franz Weidenreich who vigorously
assailed the common teaching and contended for the normality
of the cup, supporting his contention by exhaustive experimen-
tation and by ingenious argument. As might be expected these
conclusions did not pass unchallenged; heated controversies
followed in which arguments and counterarguments, rebuttals
and rejoiners held sway; technical methods were attacked;
interpretations of results were impugned. A few converts’ to
the new school were made, but the majority of workers were
unconvinced and the anatomical world at fone to say the least,
has remained highly skeptical.
In order to bring out the various disputed points it will be
necessary to present in some detail the main features of the con-
tributions of this period.
Incited by observations of Schwalbe on the porcupine and on
man, Weidenreich began an investigation, the first report of
which comprised his notable contribution of 1902. When a
moist chamber was used in examining fresh human blood (on a
warm-stage at 37.5°C.) he observed first a rapid streaming; as
the movements decreased rouleaux formed, but isolated cor-
puscles appeared as ‘bells’ (p. 464): ““ . . . . ist die wahre
3 Weidenrich (10) listed the following’as having accepted the normality of the
cup: Fuchs, Lewis, Radasch, Bonnet, Minot, Schleip, Schridde, and Stohr.
SHAPE OF MAMMALIAN RED BLOOD CORPUSCLE 443
gestalt der roten Blutktirperchen die einer Glocke mit ziemlich
dicken Wandungen .. . .” This shape he compared toa
cup (Becker), bowl (Napf), medusa, or gastrula. Identical
results were reported from a series of mammals including a
macacus monkey.
Weidenreich next asked (p. 468): ‘‘Wie kommt es aber nun,
dass man sich bisher iiber die wahre Form so tiiuschen kénnte?”’
Examining blood in 0.9 per cent sodium chloride solution he
found dises exclusively; in 0.6 per cent solution cups were seen
almost without exception. He concluded that saline solutions
exert a pure osmotic effect on the blood corpuscles; in higher
concentrations the corpuscles give up water thereby becoming
discoidal or crenated, in lower concentrations they imbibe water
and change to the cup or spheroidal condition. Since typical
cups are found in 0.65 per cent saline solution he considers this
to be isotonic with the blood of man and mammals.
Weidenreich therefore believed he was in a position to account
for the alleged popular misconception concerning the true shape
of these elements (p. 469):
Nun wird aber verstandlich, wie die Tauschung uber die wahre
Form moglich ist. Operirt man nicht sehr rasch bei der Untersuchung
des unverdiinnten Blutes und benutzt man namentlich kiltere Ob-
jekttrager und Deckgliser, so geniigt die erhébte Verdunstung der
warmen Blutfliissigkeit, um eine starkere Konzentration des Serums
herbeizufiihren; aber schon eine Schwankung des Kochsalzgehaltes
um 1 0/00 reicht wiederum hin, um eine Gestaltsveranderung der
Blutk6rperchen auszulésen. Verhindert man also die Wasserabgabe
des Blutes durch Verdunstung in der oben geschilderten Weise, dann
erhélt man auch die richtige Glockenform.
In 1903 Weidenreich learned of the recent careful freezing
point determinations which showed conclusively that the blood
is isotonic with ca. 0.9 per cent sodium chloride solution instead
of; 0.6 per cent as he believed. Hence he was forced to retract his
former view and conclude that the shape of the corpuscle is not
exclusively dependent on the osmotic pressure of the examining
medium.
In the same contribution he presented an hypothesis designed
to harmonize his previous conclusions with certain well estab-
444 LESLIE B. AREY
lished facts. Freezing point determinations have shown that
human blood plasma is isotonic with a sodium chloride solu-
tion of 0.85 per cent to 0.9 per cent in strength (Hamburger, ’02;
Hoéber, ’02; Dekhuyzen, ’01), and, according to Hamburger, a
0.99 per cent solution is isotonic with rabbit’s blood. If, therefore,
cups exist normally in the blood, why should dises be found exclu-
sively in isotonic saline solutions, whereas cups are first obtained
in hypotonic solutions of about 0.6 per cent? Weidenreich
explains away this discrepancy by assuming that there is an
elastic corpuscular membrane which varies in elasticity in salt
solution and in plasma.* There was postulated a decreased
elasticity, due to a swelling of the membrane in salt solution,
which opposes the entrance of liquid, thereby preventing the
imbibition of as much water as should enter to bring the con-
tents of the corpuscle and the surrounding medium into equilib-
rium. In other words, the internal pressure of a corpuscle in
a 0.6 per cent sodium chloride solution is greater than the pres-
sure of the plasma by an amount corresponding to a 0.3 per
cent saline solution, and this is a measure of the tension exerted
by the decreased elasticity of the’corpuscular membrane.
Additional evidence was presented in this 1903 paper. Among
other things it was stated that if blood, as it issues from a cut,
is drawn directly between two cover slips, and the preparation
rung with oil to prevent evaporation, isolated corpuscles appear
as typical cups.
In 1905a Weidenreich recommended another method for
demonstrating cups. Blood, obtained from an animal by de-
capitation or by blood letting, was defibrinated and centrifuged,
and in this serum blood was examined. Cups, not -dises, were:
observed.
Heidenhain (’04) referring to Quincke, held that the effect of
colloids on the ‘‘Molecularkraft’”? of a medium is important.
Starting from this clue Weidenreich (’05 a) reasoned that if the
4 Weidenreich was influenced by the work of Koeppe (’99) who had shown by
hematocrit methods that the swelling of corpuscles in dilute salt solutions was
not as great as it should be if osmosis alone were responsible—due, he said, to the
elasticity of the membrane.
SHAPE OF MAMMALIAN RED BLOOD CORPUSCLE 445
molecular force® of a medium opposes the expansion of a plastic
body, then by diminishing the molecular force an expansion
should result; from Quincke’s results it seemed probable that the
difference in the effect of isotonic salt solution and serum lay in
the presence of albumen in the latter. Gelatin was tried, three
per cent in 0.85 per cent sodium chloride solution. In this
medium bells were obtained, although excessive rouleaux forma-
tion and agglutination into masses occurred, making the result,
as frankly admitted, unsatisfactory.
Hence Weidenreich gradually attained the view that the
shape of a corpuscle depends on: (1) osmotic pressure, i.e., salt
content of medium; (2) ‘Molecularkraft,’ i.e., colloid content of
medium; (3) probably the elasticity of the membrane.
Hamburger (’02) found that corpuscles in lymph lost their
dise form and became cups.°
Lewis (04; 713) was the first ardent advocate of Weiden-
reich’s contention. He reported that human blood on a warm
slide shows cup-shaped corpuscles but when the slide cools and
the corpuscles come to rest the conventional discs appear.
Weidenreich’s early view that a 0.65 per cent saline solution is a
suitable examining fluid is apparently accepted and with identi-
eal results.
Stohr (06, p. 115) makes the following non-committal state-
ment: ‘‘Sie haben beim Menschen und bei den Siugetieren
die Gestalt einer bikonkaven Scheibe auch eingedellten Blase
(‘Glockenform’) oder eines flachen kreisrunden Nipfchens.”’
Heidenhain (’04), on the contrary, rejected the general cup
thesis as unproven.
By pricking his finger through a drop of vaseline Triolo (04a,
’04b) obtained an embedded droplet of blood, the coagulation of
which was said to be retarded. Examination showed spheres,
which, he states, (p. 309) were 8-10 » in diameter (cf. p. 457);
ss . . Mais, jaimais dans le sang examiné par ce procédé
de mn lubrification, on ne voit le figure classique du globule rouge:
le dise biconcave.”
5 The vagueness of this conception of the action of a ‘molecular force’ has been
justly criticized by Jolly (05).
° Cited by Weidenreich (’02).
446 LESLIE B. AREY
Jolly (04), repeating Triolo’s experiment with the blood of
the guinea-pig and man, constantly obtained dises; occasionally,
and especially at the periphery spheres or crenated forms were
seen. Weidenreich (’05b) likewise pointed out that vaseline is
not an indifferent medium and that in ordinary preparations
rung with oil, the adjacent corpuscles also ultimately become
spheres.
Jolly (05; ’06a) discredits the cup shape on the grounds that
the separating lines in rouleaux are transverse and the terminal
corpuscles usually present a plane face, as do free corpuscles.
By using oblique illumination and by observing rotating cor-
puscles David (08) became convinced that the ‘cup’ is an opti-
cal illusion which high magnifications increase. He constructed
enlarged glass models of biconcave discs and filled them with
aurantia; photographs of these taken at various angles apparently
depicted cups. ‘True concavo-convex cups, as resting forms in
blood preparations prepared as quickly as possible, were not
seen. 3
Orsés (09) was able to induce temporary mechanical distor-
tion in corpuscles but the return was to the biconcave disc which
he regards as the equilibrium form in isotonic plasma.
Lohner (’10) decided that to avoid criticism such as had been
interposed drawn blood, should be examined under conditions
which eliminated the evaporation. Accordingly he constructed
a cabinet of sufficient size to contain a microscope and into
which he could insert his hands through arm-holes; this was
heated to a constant temperature of 38°C. and the air saturated
with moisture. When the apparatus had reached a state of
equilibrium as regards moisture and temperature, blood was
drawn from a finger and examined (p. 418): ‘‘Wurden nun
unter den -angegebenen und jedenfalls ziemlich einwandfreien
Bedingungen Blutpriparate untersucht, so wurden stets und
ausschliesslich nur Erythrocyten in der Gestalt von bikonkaven
Scheiben wahrgenommen.”’ To this experiment Weidenreich
(10) replied with his familiar objection—slowness of observa-
tion, due to the awkwardness of working in a cabinet; he further
SHAPE OF MAMMALIAN RED BLOOD CORPUSCLE 447
records that red corpuscles appear as cups ves examined in
lymph from the thoracic duct.
In a later paper Lohner (’11) asserted that the cabinet did
not hamper his movements in the least, and rejoins concerning
the alleged role of evaporation. (p. 102): “Hier kommt man
jedenfalls mit dem Schlageworte Verdunstung nicht aus.”
Jordan (’09) examined drawn blood in ordinary preparations
and by means of sealed hanging drops on warmed slides. He
reports (p. 411) ‘‘that the biconcave dise form preponderates in
numbers very generally in the hanging drop and that all varia-
tions from this shape can be interpreted in terms of pressure,
contact, or contraction.”’
Recently Jordan (715) has communicated his results with the
use of Hogan’s (715) normal salt gelatin mixture, it being
claimed that this solution simulates the colloidal constitution of
blood plasma. Blood was drawn into a drop of the mixture, and
a sealed depression slide preparation made in which air was
excluded (p. 168): ‘“A rapid preliminary examination revealed
not a single indubitable cup form. Careful searching may
discover a few cups in most preparations.” The same tech-
nique applied to Tyrode’s, Ringer’s, and a 0.9 per cent salt solu-
tion gave essentially identical results. Cup forms were observed
most abundantly in ordinary preparations with Ringer’s fluid,
the cover glass being supported by a hair (p. 169): ‘“ The explana-
tion that immediately suggests itself is that the floating discs
become altered into cups through adjustment to the narrow
confines between slide and cover glass.”’
2. Results from circulating blood
Since blood may be observed intravitally in the transparent
parts of animals many extraneous complicating factors are
eliminated.
Weidenreich (’02) records his observations (p. 468):
Ich wihlte zur Priifung am lebenden Tiere ein Kaninchen; :
Wenn die Strémung recht lebhaft ist, gelingt as aller dings’ nur schw er,
ein einzelnes Korperchen schirfer in’s Auge zu fassen, bei Verlangsam-
ung des Stromes aber oder bei eingetretener Stagnation erkennt man
448 LESLIE B. AREY
dagegen leicht, dass auch hier im Profil die Kérperchen die schénste
Glockenform zeigen. Damit diifte also wohl die Beobachtung gegen
jeden Einwand gesichert sein.
In his next contribution (03) additional evidence was pre-
sented. A rat was killed by decapitation and a thin slice of
muscle observed between slide and cover. Cup-shaped cor-
puscles were seen in circulation. Weidenreich further recom-
mends for study the wing of the hibernating bat.
Lewis (’04, p. 516) reported that, in the omentum of the
guniea-pig, ‘‘The flowing bodies were seen to be flexible bodies,
somewhat variable in their proportions, some deeper, some flatter
but all that could be clearly observed were cup shaped.” <A
demonstration was made to Professor Minot who became con-
vinced of the correctness of the view (12). In his text (713)
Lewis incorporates these conclusions and figures circulating
cups.
Triolo (05) stated that the corpuscles examined by him in
the mesentery of the guinea-pig were complete spheres.
Lohner (10) viewed the capillaries in bits of excised mesentery
of the mouse and in muscle fragments. In great part-cups were
observed but a suspicion that the cups seen were not real arose
when the corpuscles emerging from the capillaries appeared as
dises; also the corpuscles within vessels viewed strictly in profile
showed constantly a disc shape. To test further this deception
Lohner .constructed a model. Colorless and colored biconcave
glass discs 5 mm. in diameter were made. These were placed
in a correspondingly large glass tube filled with fluid and the
tube laid horizontally in a fluid-filled receptacle having a glass
top and bottom. By properly choosing the liquids (alcohol in
the tube, xylol or glycerine in the outer receptacle) the effect
was said to be startling, one receiving the impression of cbse
ing typical cups.
In a series of contributions Jolly (05, 06a; ’06b; ’09) presented
the results of his studies on the circulating blood in the wings of
bats prematurely brought out of hibernation. He describes
long chains of rouleaux which fill the capillaries and break up
within the larger vessels into short segments; this phenomenon
SHAPE OF MAMMALIAN RED BLOOD CORPUSCLE 449
he considers normal (cf. Weber and Souchard, ’80). Jolly
emphasizes that the separating lines of rouleaux are transverse,
the terminal corpuscles flat, and the free corpuscles discs; excep-
tionally a cup was seen at the end of rouleaux or isolated.
Spherical corpuscles were never observed in the bat, but were
seen in the rat and guinea-pig as Weidenreich and especially
Triolo (05) had reported.
Jordon (’09) examined the omenta of two anesthetized cats
and reports that both cup or saucer shapes and discs were ob-
servable in equal numbers.
According to Schifer (12, p. 366) the cup view ‘
can not be accepted for, on examining the ee mined in
the mesentery and other transparent parts of mammals, it is
easy to observe that, with few exceptions, the erythrocytes are
biconcave.”
Of interest to the present discussion is the conclusion of Gage
(88) concerning the red corpuscles of the lamprey. These
bodies, described as cup-shaped by several workers (e.g., Giglio-
Tos, 799) are said by Gage to be biconcave discs within the
circulation.
3. Results from fixed material
The loss of the nucleus was believed by Rindfleisch (’80) to
be responsible for the early bell shape of the erythroplastids,
the subsequent assumption of the adult biconcave form resulting
from mutual impact. With a variety of fixatives, however, he
obtained cup-shaped corpuscles in adult blood.
Howell (00) considered Rindfleisch’s hypothesis erroneous
(p. 103): “It seems to me very natural to suppose that the
biconeavity of the mammalian corpuscle is directly caused by
the loss of the nucleus from the interior.”
Malassez (96) found 2 per cent osmic acid produced cups,
and complete spheres.
Cup-shaped corpuscles were described by Dekhuyzen (’99)
as a transient developmental stage, yet he records that his assis-
tant, Blote, obtained bells when blood was drawn into osmic
acid. Heinz (’01) likewise held cups to be immature forms and
also described nucleated cups.
450 LESLIE B. AREY
Fuchs (’08) decided that Zenker fixation preserved the origi-
nal cup shape, whereas he had formerly thought the cup to be an
artefact:
Osmie acid was found to produce cups and spheres by Jolly
(05), who, however, questioned the significance of the result
(06 a) because he believed swelling occurred. Later (’09), hav-
ing first observed circulating discs in the bat’s wing, he fixed an
area in situ with 1 per cent osmic; after fixation the corpuscles
were found to be spheres.
Lewis (’04) showed that pricking through a drop of osmic
acid produced many shrunken corpuscles and cups. Zenker’s
fluid acts violently on drawn blood. From the study of the
tissues of various mammals he concludes (p. 516): ‘‘In preserved
mammalian blood the typical red blood corpuscle is cup shaped.
The biconcave dise is but one of several forms of shrunken
eups’’ In 1913-he “again says (po. 192): ““.- 5 2. 2 amare
preserved tissues of all sorts, and with all fixatives such as are
relied upon to reveal the structure of other tissues the mam-
malian erythrocytes are typically cup-shaped. . . -. where
the tissues in general are excellently preserved the corpuscles ap-
pear as cups. The biconcave dises are flattened cups.”’
Weidenreich (’02) considers the evidence gained from the use of
fixatives (e.g., 1 per cent osmic acid) alone sufficient to establish
the cup shape. In 1905 b he stated that osmic acid preserves
corpuscles which have become discs as dises. _ Later (’06 a) he
recommended a rapid method for preserving smears by osmic
acid vapor; the form was said to be fixed in three to five sec-
onds, this being less time than is required for the corpusles to
change shape osmotically.
Human material, several hours old, was preserved by Radasch
(06). Several organs of the body were examined, including
the placenta with its maternal and fetal blood. A large majority
of cups were observed.
Jordan (’09) records his experience with fixatives although he
discounts the value of evidence obtained by such methods.
With various reagents cups, irregular forms, and a few irregular
discs were found whereas in one Zenker-fixed preparation discs
SHAPE OF MAMMALIAN RED BLOOD CORPUSCLE 451
preponderated. He concludes that fixation causes contraction,
which is probably unequal at the center and rim, thereby pro-
ducing cups.
Lohner (711) elaborated this latter view. The coagulation of
fixation involves a diminution in diameter. By experiment he
showed that when blood issues from a puncture of the skin into
a drop of fixative, or when it is drawn by capillarity into osmic
acid between two cover glasses, the conditions are present for
an unequal action of the fixative with a resulting distortion of
the corpuscles. Corpuscles meeting the fluid edge foremost
become wedge-shaped; when the flat surface is first fixed a cup
results. Dises are obtainable provided the fixation is uniform.
Wiedenreich (710) accused Lohner (710) of being inconsistent
(p. 448), for in living animals he held cups to be illusions and in
drawn blood he considered them artefacts. Having observed
cups in a portion of excised mesentery, Weidenreich added fixa-
tive and still saw cups, which, he said, were not illusions, for if
squeezed from the vessels they retained the cup appearance.
Lohner (‘11) interpreted this experiment as follows. In the
vessels there are discs which may give a deceptive appearance of
cups, as well as temporary cups due to distortions, and real cups.
The apparent cups were changed to artificial cups by the fixa-
tive; hence this form was seen when the corpuscles were pressed
from the vessels.
It is evident from the foregoing résumé that the normal shape
of the erythroplastid remains undetermined. The hope of ob-
taining new evidence on this fundamental question has induced
me to undertake the present work, concerning which a prelimi-
hary communication has already been published (Arey, 16).
C. OBSERVATIONS
1. Experimentation with drawn blood
In ordinary preparations of undiluted blood, made as quickly
as possible and examined between warm slides and covers, I
have usually observed a few cups intermingled with large num-
bers of discs. The transformation of cups into dises, which
452 LESLIE B. AREY
according to Weidenreich and Lewis occurs largely prior to
microscopic inspection, [ have never seen, and, so far as I am
aware, no one asserts to have actually traced this transformation
in individually scrutinized corpuscles. With the formation of
rouleaux the apparent number of dises is, of course, increased,
for more are seen on edge.
The factors which might be suspected as responsible for this
alleged alteration are decreased temperature and increased con-
centration of the plasma. Weildenreich, in particular, has in-
sisted on these factors as causing the widespread ‘deception’
concerning the true shape of the blood corpuscle.
The statement that the evaporation and consequent concen-
tration of a blood droplet, before the preparation can be made
and examined, is sufficient to inaugurate these modifications can
not be arbitrarily dismissed no matter how improbable it may seem
in the light of the readily observed effects of dilution and con-
centration upon the shape of red corpuscles; when, however, a large
drop of blood is used the concentration change must be slight.
But that it is necessary to maintain an elevated temperature to
prevent rapid evaporation (Weidenreich, ’02) is as astonishing
as a statement as it is embarrassing to defend as a doctrine
(cf. p. 443).
The momentary exposure to air necessitated in making ordi-
nary preparations may practically be eliminated by using the
following procedure. Superimposed cover glasses, separated by
a hair, are fused at one point by heat; if an edge be now applied
to a needle prick in the finger the issuing blood is drawn by capil-
larity between the two surfaces. Such preparations, examined
quickly with or without the aid of the warm stage, have never
yielded evidence for the general existence of the cup shape. <A
few cups may usually be found whereas scores of indisputable
dises appear.
Since only corpuscles viewed edgewise furnish reliable data as
to shape, any pressure effect from the approximation of the slide
and cover glass in the foregoing experiments will tend to increase
the number of cups seen.
SHAPE OF MAMMALIAN RED BLOOD CORPUSCLE 453
The experiments in which Weidenreich (05 #) added gelatine
to 0.85 per cent saline solution in order to reduce the ‘Molecular-
kraft’ have been described (p. 445). Admitting the results to be
unsatisfactory, he, nevertheless, features them prominently and
emphasizes their significance (05 a;’05b). If the reeommended
three per cent gelatin (purified and dialized) be added to 0.85
per cent sodium chloride, or to Tyrode’s solution, a medium is
obtained which is a dense gel at room temperature. This obvi-
ously does not simulate blood plasma, but it was chosen, we are
told, because it is the optimum concentration and gives the best
results.
When the finger is pricked through a drop of this gel and the
resulting mixture is, examined in a hanging drop, abundant
rouleaux form, and the corpuscles commonly agglutinate into
amorphous masses or become distorted and tailed. Cups of
various shapes and some dises are also to be found. If the
foregoing experiment be duplicated, except that an assistant by
means of a needle mix the small droplet of issuing blood evenly
throughout the gelatin, the resulting preparation more closely
approximates the normal. Furthermore, the number of discs
seen is increased. The distorted, agglutinated, and ruptured
corpuscles in the first case are apparently referable to the resis-
tance of the dense gel; the issuing blood as it breaks up into tiny
streamlets which dart along irregular paths in the gel following
the line of least resistance testifies strikingly in favor of this
probability.
When the 3 per cent gelatin mixture is warmed it changes to
the sol condition. If a small droplet of blood be drawn into a
drop of the gelatin solution at body temperature, care being
taken as before that the mixing is even, rouleaux formation
need hardly exist. Moreover, large numbers of typical bicon-
cave discs are observable in edge view; a few cups may also be
found. I therefore conclude that with certain precautions this
experiment proves the precise converse of that which Weiden-
reich designed it to show. Confirmatory results are found in the
recent work of Jordan (’15) who decides that human red blood
THE AMERICAN JOURNAL OF ANATOMY, VOL. 22, No. 3
454 LESLIE B. AREY
corpuscles are biconcave dises in Hogan’s normal salt-gelatin
mixture which contains 2.5 per cent gelatin.
But the foregoing evidence is not crucial. Blood is not a gel
at room temperature; neither does it contain gelatin; nor is
the arbitrarily chosen 3 per cent solution rational. If colloids
are to be added it is highly desirable to use the proper amount
of the protein normally present in blood.
Beside fibrinogen these proteins are serum albumin and serum
globulin. Due to the conditions imposed by the world war I
was unable to obtain serum globulin but did procure a purified
sample of the closely similar serum albumin (Merck). To Ty-
rode’s solution, which is claimed to duplicate accurately the
inorganic composition of blood, was added enough serum al-
bumin (re-dialized to make certain of its purity) to correspond
to the amount of both albumin and globulin normally present in
plasma. Blood corpuscles examined in this diluting medium
proved to be almost exclusively discs.
Experimentation with undiluted blood is, at its best, unsatis-
factory. The crowded conditions, the tendency toward rouleaux
formation and coagulation which make such preparations un-
favorable are obviated by the use of diluting media. If, how-
ever, artificial ‘physiological solutions’ be used, the results may
ever, though perhaps unjustly, be subjected to criticism. At
best these are artificial media, the tonicity and colloidal consti-
tution of which may or may not simulate blood plasma. To
preclude such criticisms natural serum must be used. Accord-
ingly I had 20 ce. of blood drawn from my basiliec vein. This
was defibrinated by whipping and centrifuged quickly; thus an
examining medium was obtained, identical with blood plasma
except for the loss of one of its minor protein constituents—fibrin.
By utilizing an electrically heated warm-stage a hollow-cen-
tered life slide, cover glass, and the air of the cell itself may all
be maintained constantly at body temperature. A drop of
serum’ was placed on a finger previously cleaned with alcohol,
and the finger pricked through the drop. The diluted droplet
7 Previous microscopic examination had made certain that the serum was free
from blood corpuscles.
SHAPE OF MAMMALIAN RED BLOOD CORPUSCLE 455
of blood, thus obtained without direct contact with the air, was
touched to a cover and suspended, as a hanging drop, in the
life cell. Vaseline served to seal the cell, the air in which could
be kept saturated with moisture by previously introducing a
drop of water and sealing. The entire procedure demands no
more time than in making ordinary preparations; if a large drop
of serum be used, the evaporation prior to sealing is inconsider-
able whereas further evaporation within the life cell can not
occur.
A microscopic examination of blood prepared according to
this technique reveals numerous isolated corpuscles. <A favor-
able place for scrutiny is near the center of the drop. Here
sinking corpuscles revolve slowly, showing alternately their two
faces. Usually a few cups can be found, whereas quantities of
biconcave discs are seen in every field.2 Streaming movements
initiated by rolling the suspended drop towards the edge of
the cover also allow many corpuscles to be viewed from both
surfaces.
Another technical procedure, used by Jordan (715) in his
experiments with physiological solutions, consists in filling
shallow concave slides with serum into which the drop of diluted
blood, prepared as before, is introduced. Evaporation is_ pre-
vented by immediate sealing with a cover glass and vaseline.
Body temperature is maintained by the aid of the electrical
warm stage. The conclusions drawn from the study of many
such preparations substantiate those already reached with the
hanging drop.
The necessity or desirability of observing blood which has not
been allowed to cool has been emphasized by those who uphold
the normality of the cup shape. Weidenreich (’02) contended
that the use of cold slides and covers is largely responsible for
the widespread ‘deception’ as to the true shape of the red cor-
puscles; in his contributions of 1903, 1905 and 1910, however,
he apparently abandons this contention for he urges only the
necessity of rapid manipulation. Lewis (’04) states that as the
8 Room temperature 27°C.
9 The dise shape is retained in properly sealed preparations 48 hours old.
456 LESLIE B. AREY
preparation cools the cups become biconcave discs arranged in
rouleaux. From my personal experience I do not believe that
temperatures between 0°+ and 40°C. directly condition the shape
of the erythroplastids. Hanging drop preparations, cooled for
several minutes on pulverized ice, precautions being observed to
prevent dilution of the drop by condensation of moisture, show
no essential difference from those at body temperature examined
immediately; if retained for 10 minutes the free corpuscles are
also typical discs. Subnormal temperature of itself induces
neither crenation nor rouleaux formation. These tests merely
show that cooling does not modify the shape of the disc; those
who defend the cup shape would maintain that an almost in-
stantaneous change from cup to dise had already occurred while
the preparation was being made.
Experimentation with other samples of human serum has been
possible through the kindness of three of my colleagues.'° The
results obtained both when corpuscles were examined in their
own serum and in each of the other three sera were identical
with those already described. More cogent proof concerning
the primary shape of the human erythrocyte to be derived from
the study of drawn blood, I can not imagine. Similar extensive
tests have likewise been made with 0.85 per cent and 0.9 per
cent saline solutions and with Tyrode’s solution;! the latter is
claimed to simulate blood plasma more closely than other phy-
siological solutions with the possible exception of Hogan’s
mixture.
It is a familiar fact that the dilution of drawn blood with
water causes the red corpuscles to assume a spherical shape,
whence they ‘lake’ and become colorless spheres; on the con-
trary media stronger than normal plasma crenate the corpuscles.
Various dilutions of human serum in distilled water were next
prepared and used as dilution media for hanging drop prepara-
tions. The ultimate concentration of any mixture obtained by
10 Prof. S. W. Ranson, Mr. L. H. Kornder, and Mr. M.R. Waltz. For opera-
tive assistance I am indebted to Dr. Joseph Jaros.
11 For formula see Rona, P. und Neukirch, P., 1912. Archiv f. d. gesam.
Physiol., Bd. 148, pp. 273-284.
SHAPE OF MAMMALIAN RED BLOOD CORPUSCLE 457
adding a droplet of blood to a diluted serum obviously depends
on the relative amounts of each used. It is believed that the
percentages stated in the following paragraph are sufficiently
accurate for the purpose at hand.
When a droplet of blood is mixed with human serum contain-
ing ca. 25 per cent water some erythroplastids assume the shal-
low cup shape shown in figure 1, B; most, however, remain as
biconcave discs (A). When ca. 40 per cent water is present
there is a great preponderance of typical cups, with here and
there an unchanged disc. These cups appear somewhat like
figure 1, D in ca. 50 per cent mixtures. In dilutions containing
ca. 60 per cent water, the walls of the cups become swollen and
the concavity is reduced (/); this imbibition is so marked in
mixtures of ca. 65 per cent water that the appearance is that of
deeply dimpled spheroids (F’). Perfect spheres result when the
water content of the mixture is ca. 70 per cent.'2 In concen-
trated serum erythroplastids crenate.
It is evident, therefore, that the shape of a corpuscle is, at
least in part, a function of the concentration of the medium,
the changes being referable to the action of osmotic pressure.
In progressively hypotonic solutions the corpuscles imbibe in-
creasing amounts of water, ultimately becoming spheres: and
laking. In hypertonic media, water is given up and crenation
results. All corpuscles, however, are not affected similarly by
the same concentration. This is strikingly shown by crenation
experiments and especially by dilution phenomena. When the
percentage of water present is 25, only part of the corpuscles are
clearly affected. Such a result might conceivably be due to the
unequal elasticities of the corpuscular membranes which oppose
differently imbibitory swelling.
Analogous series were obtained by diluting Tyrode’s solution
and 0.85 per cent saline with distilled water. The shapes of the
red corpuscles at the various dilutions approximated closely
2 The following measurements hold:
Diameter of dise 7.
7
5
Diameter of cup .0=
Diameter of sphere 5.0
458 LESLIE B. AREY
those already described when human serum was used. This
result supports the standard freezing point determinations of
Hamburger (’02), Hober, (02) and Dekhuyzen (’02) which find
human plasma isotonic with an 0.85 to 0.9 per cent saline solu-
tion. On the contrary it militates directly against the conclu-
sion of Weidenreich and Lewis, who, notwithstanding the deter-
minations just alluded to, hold that a 0.6 to 0.65 per centy salt
solution is isotonic with human plasma; these workers have
G
D E F
Fig. 1 Profile sketches illustrating the shape assumed by the human erythro-
plastid in various dilutions of human serum with water. A, in undiluted serum;
B, ca. 25 per cent water; C, ca. 40 per cent water; D, cd. 50 per cent water; EH,
ca. 60 per cent water; F, ca. 65 per cent water; G, ca., 70 per cent water.
arrived at this point of view in the following way: blood issuing
from the veins is supposed to change suddenly from the cup
to the disc shape, due presumably to a slight concentration
through evaporation (or to loss of heat; Lewis?) ; onintroducing
drawn blood or blood diluted in 0.9 per cent salt solution saline
discs become cups, hence the cup shape is normal and a 0.6 per
cent salt solution is isotonic with plasma.
It was found that erythroplastids not only assume shapes
which are correlated with the concentration of the medium but
that these changes are also repeatedly reversible. Typical
experiments will illustrate this behavior.
SHAPE OF MAMMALIAN RED BLOOD CORPUSCLE 459
Experiment 1.6.1. A drop of human blood, diluted in human serum,
on examination showed the erythroplastids to be typical discs. When
a droplet was transferred to a hanging drop, composed of half serum
and half water, the corpuscles assumed cup shapes (fig. 1, 6). The
disc shape was recovered by retransferring to normal serum but in
the 50 per cent serum-mixture swollen cups (like fig. 1, /) were again
obtained. Following a return to discs in normal serum, crenation was
effected by transference to somewhat concentrated (evaporated)
serum.
Experiment 1.6.2. Disc-shaped corpuscles in normal serum cre-
nated in hypertonic serum. Transference to serum diluted one-half
with distilled water induced a return to discs for some corpuscles and
to cups for others. In hypertonic serum crenation again occurred.
As the size of the droplet used in the transfer affects greatly
the ultimate concentration of the mixture, the figures given in
these experiments have no quantitative value. Considerable
variability was found in the responses of individual corpuscles.
It is perhaps significant that in experiment 1.6.1 the second
transfer to dilute serum produced more highly swollen cups
(fig. 1, F) than did the first transfer (fig. 1, B); that it is indica-
tive of an increased elasticity of the corpuscular membrane
through injury is not impossible. Corpuscles in which crena-
tion has proceeded too far seem to be permanently injured and
incapable of a return to the normal; similarly figure 1, /, marks
the approximate stage beyond which corpuscles become irre-
versibly altered. In terms of saline solutions these limits cor-
respond to concentrations between 0.9+ per cent and 0.3 per
cent. The possibility of the action of a toxic time factor was
not investigated.
The importance of these diverse dilution phenomena on the
question of the normal shape of the human erythroplastid seems
to me paramount. Since within wide limits the form of a cor-
puscle depends on the concentration of its medium, how can the
cup shape be normal when human serum must be diluted at least
one-third to produce this type?
Experimentation with the serum of the cat and dog, both as
regards their own corpuscles and those of other individuals and
of man, has confirmed the conclusions already reached concern-
ing the normality of the biconcave disc.
460 LESLIE B. AREY
With the guinea-pig, rat, and rabbit I have obtained variable
results. The corpuscles of one guinea-pig examined in their
own serum were constantly dises; in another specimen, tested
twice in four days, it was impossible to find corpuscles except
in crenated condition; in a rabbit it was difficult to obtain prep-
arations which did not show extensive crenation in their own
serum; although human blood in this serum showed dises almost
exclusively. The blood of a white rat examined in its ownserum
had one-half or more of the corpuscles strongly cupped; the
blood of two other rats examined in the serum of the first also
showed a majority of cups, although human blood corpuscles
remained discs. When serum from one of the last mentioned
rats was prepared its own corpuscles were discs, as were also
the corpuscles of the third individual. I have not worked on
many individuals of these species which have been used so ex-
tensively by other experimenters (Weidenreich, Lewis, et al.),
but the variable results just cited do not inspire confidence in
the employment of this class of animals; from my experience
they are untrustworthy and unfavorable material. The un-
tested suggestion presents itself that in those rodents which usu-
ally do not drink water, but depend on green vegetables for their
supply, the concentration of the plasma may vary; external
temperature (the above tests were made in June) and the rations
of the average animal house perhaps play no inconsiderable
role.
2. Examination of circulating blood
Blood observed circulating in the transparent parts of mammals
should furnish extremely reliable data concerning the question
at hand. There are, however, certain technical difficulties to
be overcome, as well as the infeasibility of observing rapidly
moving corpuscles under high magnifications.
It is conceivable that the pressure on the delicate vessels,
caused by the ordinary use of a cover glass and oil immersion
objective applied to the omentum (Jordan, Lewis, et al.) might
induce the assumption of the cup forms ‘through narrowing
the confines to which the delicate discs must adjust themselves”
SHAPE OF MAMMALIAN RED BLOOD CORPUSCLE 461
(Jordan). To avoid this pressure I employed an immersion
objective with Tyrode’s solution, as in the water-immersion
lenses of former days; in this way the spread omentum was ob-
served directly without the aid of a cover glass. A Leitz no. 4
dry objective and a no. 12 compensating ocular, with the draw
tube of the microscope set at 190 mm. also gave a very satis-
factory magnification and was used extensively as a check on
the wet method.
The omenta of eight cats and two dogs were studied continu-
ously for periods from one to four hours. The animals used were
purposely in a state of deep surgical shock resulting from previous
laminectomies; in each case the anesthetic had been stopped two to
four hours prior to the experiment.
Capillaries of smaller calibre than the diameter of an erythro-
plastid are obviously unsuited for observational purposes. Both
the vessels figured by Lewis (’13) are open to this objection;
of the eight cup-shaped corpuscles shown in edge view, six if
flattened to dises would exceed considerably the diameter of
their containing vessel.
Regions of the omentum where temporary stases have caused
corpuscles to adhere in clumps or agglutinated masses I do not
consider favorable; when the flow is resumed many cups are
seen, the cup form apparently being in some way referable to
the former massed condition."* The rapidity of normally cir-
culating blood makes it impossible to observe satisfactorily the
individual corpuscles which pass across the field as an ill-defined
blur; in the rhythmical release from stasis which sometimes
occurs in a pulsating fashion the corpuscles are mutually com-
pressed to an unfavorable degree.
Since ordinary circulation is much too rapid to enable accu-
rate observation, I believe that the most reliable data are obtain-
able under the following conditions. It is sometimes possible
to find a bifurcation of precapillary or larger vessels in which
13 Tt is to be noted that Weidenreich (’02) made his observations when the
current had slowed to the point of incipient stasis.
14 Such illustrations of corpuscles within vessels, as figured by Lewis (13)
could not have been drawn from normally circulating blood as the legend implies.
462 LESLIE B. AREY
the flow selects one limb almost exclusively, separate corpuscles,
nevertheless, being intermittently ‘kicked off’ into the slowly
moving plasma of the other limb." Such a situation, where the
current in the main vessel is rapid and normal (to find which
often necessitates considerable diligent search), I regard as most
favorable for study. Criticisms of pressure, agglutination, and
of observing vessels so small that the corpuscles must necessarily
adjust themselves to their exiguous confines are obviated.
Erythroplastids emerging from the main stream one or two
at a time in the manner indicated were found to be discs; most
of these corpuscles are revolving when first seen and it is easy
to be certain of their biconeavity. In such situations I have
observed hundreds of discs with only an occasional cup- or sau-
cer-form;!® this observation has been corroborated by several
of my colleagues.
In anesthetized guinea-pigs and rabbits, cups were very com-
mon, and in a dog under ether anesthesia a great preponder-
ance of cup shapes was observed. The query immediately
presents itself whether under these conditions the anesthetic is
responsible for the cup shape. The following experiment is
highly suggestive:
Experiment 1.4.1. Hanging drop preparations of human blood and
the blood of the cat, dog, guinea-pig, rabbit, and rat, diluted with
serum, were made. When a drop of ether or chloroform was now
introduced into the bottom of the life cell the drop took on the vapor
and the discs were seen to change rapidly through the various cup-
shapes to spheres, finally laking and becoming shadows.”
I believe that my observations indicate that the erythroplas-
tids of normal circulating mammalian blood are biconcave discs;
15 For making these observations I can particularly recommend the dog.
16 Perhaps the number of cups is somewhat increased by the presence of cor-
puscles brought by the capillary net from regions of the omentum in stasis.
17 A curious surface tension effect was obtained when corpuscles were re-
moved from a hanging drop of Tyrode’s solution before the effect of the anes-
thetic had proceeded far. On transference of these cupped forms to a drop of
pure Tyrode they became dises whereupon some moved edge foremost across the
field with a wobbling motion for longer or shorter distances then turned abruptly
and continued at an angle. This would be repeated for some time.
SHAPE OF MAMMALIAN RED BLOOD CORPUSCLE 463
the burden of proof rests on those who have used anesthetized
animals (and apparently most previous workers have done so)
to show that the anesthetic held in the blood is not responsible
for the preponderance of cups observed.
3. Action of fixatives
Many workers have recorded that mammalian tissues pre-
served in various standard fixatives contain cup-shaped erythro-
plastids. Those who uphold the normality of the cup have laid
great stress on this line of evidence particularly in view of the
fact that ‘‘in well preserved tissues of all sorts, and with all
fixatives such as are relied upon to reveal the structure of other
tissues, the mammalian erythrocytes are typically cup-shaped”’
(Lewis).
Smear preparations, such as advocated by Weidenreich, would
hardly seem to furnish reliable data concerning the moderately
flexed saucer shapes which are held by these workers to be the
normal intravital form. It is necessary that the corpuscles be
observed more of less on edge.
An examination of what is ordinarily called well-preserved
mammalian tissues demonstrates convincingly that the cup
shapes are indeed preponderatingly abundant within the ves-
sels.'8 With Jordan (’09), however, I must deny the univer-
sality of this statement. Occasionally tissues have been observed
in which the corpuscles seen were discs almost exclusively. Not
only have cups and dises been observed within the same vessel,
but rarely vessels, have been found side by side, one containing
cups, the other discs.
I have fixed small pieces of human vascular fat, obtained fresh
from operations, in 1 per cent osmic acid, in saturated subli-
mate in 0.75 per cent sodium chloride, and in the fluids of Zen-
ker, Orth and Helly. In each case only a few moments elapsed
between the removal of the tissue and its immersion in the fixa-
tive. Celloidin sections showed constantly a great preponder-
ance of cups.
18 Sites must of course be chosen where the corpuscles are well separated.
464 LESLIE B. AREY
In view of the rapid action of hypo- or hypertonic salt solu-
tions in changing the shape of corpuscles an attempt was made
to discover whether the concentration of the fixative could influ-
ence the shape of the corpuscles before fixation occurred. Zen-
ker’s fluid was practically saturated with cane sugar or with
sodium chloride and fresh human tissue fixed as before. The
result was unchanged; the corpuscles became cupped.
When to drawn human blood, diluted in human serum, is
added the fluids of Zenker, Helly, or Orth, cups, dises, and dis-
torted forms are seen. The action is more violent than when
blocks of tissue are preserved in the same fluids. With Zenker
an especially curdy coagulum forms, whereas in Orth there is
only a fine granular coagulum; in the first named fixatiye cups
are abundant, in the latter many fine dises may also be obtained.
In Perenyi’s fluid the corpuscles assume a peculiar pitted
appearance. .
If the finger be pricked through a drop of 1 per cent osmic
acid solution, the fixed corpuscles show many cups as well as
discs, wedge shapes, and distorted forms. If a drop of blood be
first exposed to the air and the osmic acid then added, a greatly
increased number of dises are seen, although discs are by no
means exclusively present as Weidenreich (’05 b; ’10) would have
us believe. These facts have been advanced in support of the
normality of the cup shape, for it is argued (Weidenreich ’06 c)
that osmic acid must give faithful preservation since it fixes not
only the cup but also dises which have been formed from cups
after exposure to air.
The query immediately arises as to the weight which should
properly be given to evidence derived from the action of fixa-
tives. Weidenreich (’02), for instance, considers this evidence
alone sufficient to establish the cup form (ef. also Lewis 713).
The fact, however, must not be lost sight of that these cor-
puscles are plastic structures of extreme delicacy, mere contact
with adjacent corpuscles or obstacles sufficing, when gentle
streaming is induced, to cause excessive and varied temporary
distortions. Fixation is essentially a coagulation process and it
has been shown (Weidenreich ’06 b) that the so-called best fixa-
SHAPE OF MAMMALIAN RED BLOOD CORPUSCLE 465
tives actually diminish (i.e., shrink) the diameter of the cor-
puscle. If this shrinkage were unequal at the thin center and
thick rim a dise might conceivably become a cup, as Jordan
maintains. Furthermore, if the reagent does not act on all sides
of a corpuscle simultaneously, is not a buckling of the more con-
tracted side on which the reagent first acts to be expected?
Indeed, the preéxistence of biconcavities would favor this altera-
tion. It seems plausible that the delicately constructed erythro-
plastid is more easily subject to distortion, through the action
of reagents, than are ordinary tissue cells, for it is neither sup-
ported by contiguous cells nor by intercellular products.
If this reasoning be sound the variable action of osmic acid
on drawn blood allows of another interpretation. When blood
enters a drop of fixative directly from a minute needle prick in
the finger the conditions for unequal fixation would appear to
be present (Lohner). Besides cups, numerous wedge-shaped
corpuscles are seen; according to the conception of uneven fixa-
tion such forms are easily explained. The presence of more
dises in blood that has first come into contact with air need not
be interpreted as due to a rapid change from the cup to the dise
with a subsequent fixation of the latter form; assuming that such
corpuscles have not been exposed to air sufficiently to induce
incipient crenation, which conceivably could affect the physical
condition of the corpuscular membrane (without, however,
necessitating a change in form), the result is explainable on the
basis of a more even intermixing of blood and the added fixative.
The following experiment of Lohner (11) which I have often
corroborated is instructive from this viewpoint:
Experiment 2.1.3. If a droplet of blood be drawn by capillarity be-
tween two cover slips, separated by a hair and fused at one point, discs
are observed. (Blood should occupy part of the capillary space only.)
If 1 per cent osmic acid be now drawn in cautiously from one side
only, the conditions for uneven fixation are present and many cups,
some wedge-shaped discs, discs, and distorted forms are seen.
D. DISCUSSION
Only certain aspects of the problem of a more or less general
nature will be considered here, critiques of individual results and
466 LESLIE B. AREY
methods having for the most part been introduced in connection
with the previous section.
We have seen that the examination of undiluted drawn blood
has led various workers to diametrically opposed conclusions.
Those who champion the cup form believe that a rapid trans-
formation of cups into discs, before preparation are made and
examined, is responsible for the finding of discs by slower mo-
tioned workers. The whole cup hypothesis, therefore, hangs on
the sudden secondary transformation of cups into discs whenin
contact with the air. The reproach of slowness, which has
been repeated so frequently is, nevertheless, not incontestable
but is open to scrutiny and analysis.
Two factors have been emphasized as responsible for the
alleged sudden mutation of shape. Weidenreich (’02) and Lewis
(05; by implication) urged the necessity of maintaining normal
temperature if cups are to be seen: Weidenreich’s position was
obviously untenable (p. 452) and in his papers of ’03, ’05a, and
"10 he abandoned his insistence on temperature as a causative
modifying agent. The second factor is that of evaporation
resulting in an effective concentration of the plasma, before
drawn blood is observed. By drawing in blood, as it issued
from the cut, between two parallel cover glasses fused at one
point, the exposure to air before examination was reduced to a
minimum (p. 452) yet I am not able to conclude that these ex-
periments support the cup theory. Loéhner’s (’10) tests with his
constant-temperature and moisture-saturated cabinet (p. 446)
precluded evaporation, yet he obtained ‘‘stets und ausschliess-
lich” biconcave discs. In the experiments in which I diluted a
droplet of blood in a large drop of human serum, without the
blood first coming in contact with air, the increased concentra-
tion of the.mixture during the few seconds before the preparation
was sealed must have been negligible; when it is further dis-
covered (p. 457) that human serum must be diluted one-third to
obtain cups, the futility of the evaporation argument becomes
apparent. For these reasons I am unwilling to admit that the
evidence derived from undiluted drawn blood either establishes
or supports the normality of the cup.
From the work of Ranvier in 1875 it has been known that,
SHAPE OF MAMMALIAN RED BLOOD CORPUSCLE 467
graded temperatures can alter disc-shaped corpuscles to deep
cups, thick-walled cups, or even to spheres, e.g., typical cups
are found exclusively when blood is warmed to 55° (Zoth). It
is impossible that some investigators who advocate the cup
shape have unduly heated their slides and covers (perhaps in
attempting to allow for cooling when warm stages were
not available) in overzealous attempts to maintain normal (!)
- conditions.
We have seen (p. 444) that Weidenreich, at a loss to reconcile
the cup shape of corpuscles in 0.6 per cent salt solution with the
disc shape in the well established isotonic 0.9 per cent first held
as responsible a decreased elasticity of the corpuscular mem-
brane in saline solutions; later he shifted the emphasis to a
hypothetical influence of a changed ‘Molecularkraft’ in the
solution due to the presence of colloids. Both the results of
Jordan (715) with Hogan’s normal salt-gelatin mixture and my
own in repeating Weidenreich’s experiment are not in agreement
with the latter’s conclusion; hence I believe that Weidenreich
is still confronted with his original dilemma. This conviction
is strengthened by the fact that when serum albumen was added
to normal saline and Tyrode’s solutions in an amount which
duplicated the protein content of blood plasma, I obtained an
examining medium in which the corpuscles were unquestion-
ably dises.
Since the results of freezing point determinations are not
accepted by those who champion the cup shape as giving reliable
information regarding the isotonicity of physiological salt solu-
tion (p. 448), it is evident that the use of artificial media alone
serves only to incite controversy. For these reasons much of
the work of Weidenreich and that of Lewis (05) and Jordan
(15) with respect to this point is in itself not crucial. If one
believes in the cup shape and is able to obtain this form only in
0.6 per cent instead of the accepted isotonic 0.9 per cent saline
solution, he of course can ever invoke the aid of extraneous fac-
tors to explain the discrepancy. The escape from this quandary
lies in using serum as the diluent. I have already given my
reasons (p. 460) for distrusting the data obtained from the use
of the rat, guinea-pig, and rabbit. Hence I must for the pres-
468 LESLIE B. AREY
ent remain skeptical concerning the value of data obtained from
these animals both as regards the corpuscles of their undiluted
blood or from the use of their blood sera and lymph as diluting
media. On the other hand in my experiments (p. 454) in which
the blood of the cat, dog, and man (four individuals) was ex-
amined both in their own sera and each of the other sera, I con-
stantly obtained biconcave discs almost exclusively. Further-
more, the necessity of diluting human sera one-third with water
to obtain the cup-shape is to my mind incompatible both with
the doctrine that the cup shape is normal and with the view that
a 0.6 per cent salt solution is isotonic with human plasma.
In studying the circulating blood of living mammals the re-
sults recorded in this paper were obtained without involving the
possible distortion of corpuscles through pressure from a cover
glass and oil immersion objective as has formerly been the case.
Although I am not altogether certain that this is a real danger,
as Jordan (715) believes, it is, nevertheless, easily and properly
avoided. If capillaries of too small calibre to possibly allow the
assumption of the dise shape (p. 461) be not chosen and if blood
which is not, and has not been in stasis be observed in non-
anesthetized cats or dogs, I feel sure that my observation of a
great preponderance of discs can be verified, Here, again, the
animals formerly used have largely been either guinea pigs or
rabbits whose appropriateness is questionable. Since ether and
chloroform visibly change dises to cups or spheres (p. 462) those
who make use of anesthesia must disaprove its effect intra vitam.
Weidenreich (’03) reported cups in the wing of the living bat -
and asserts that the dises seen by Jolly (’05; 06a; ’06 b; ’09) in
the same location represent cups which had previously formed
rouleaux, these being again resolved into their constituent ele-
ments and. then appearing as discs. One would like to know
more about the details of these experiments. Were anesthet-
ics used? Jolly animals were brought out of hibernation and
showed excessive rouleaux formation which he considers a normal
intravital condition but which is more likely referable to the
recent hibernating condition or to partial stasis. No details of
his observations are given by Weidenreich except that he used
SHAPE OF MAMMALIAN RED* BLOOD CORPUSCLE 469
a hibernating bat. For several reasons the bat might be ex-
pected to furnish valuable evidence on this problem and arrange-
ments are under way by the writer for the further study of these
animals.
David (’08) first called attention to the resemblance which a
biconcave disc, viewed obliquely, bears to a cup, a deception
which is intensified by high magnifications and which he illus-
trated by photographing glass models. Lohner (’10) developed
this idea and constructed an elaborate model (p. 448) which was
said to corroborate his view. That a biconcave corpuscle strik-
ingly simulates a cup when viewed obliquely is true, but that
this illusion alone has influenced a decision on the part of other
observers favoring the cup shape seems improbable. Cups and
dises viewed in profile are unmistakable and it is from profile
views that crucial evidence must be derived.
But little need be added regarding the action of fixatives.
_ Serious doubt has been cast on the trustworthiness of standard
fixatives in preserving the original shape of red blood corpuscles
(p. 464). Both Radasch and Lewis regard discs as represent-
ing collapsed cups; ‘“‘It may be thought that the depression
which makes the cup is itself due to shrinkage, or due to vacuole
formation. The only proof to the contrary is to be had from
the circulating blood of a living mammal’” (Lewis ’04, p. 516).
A critique of the methods and results of this ‘only’ source of
proof to the contrary has been sufficiently dealt with in the
foregoing pages.
It is interesting that agents such as heat (Ranvier, ’75), elec-
tricity (Lohner, ’07), and ether or chloroform produce cups from
discs. It is perhaps significant that these so-called destructive
agents in each case alter discs to cups, not the reverse.
A limited and probably inconstant number of cup-shaped
erythroplastids undoubtedly are present in normal blood. Pos-
sibly they represent corpuscles, whose structure is such that
unequal tensions with respect to themselves or to the osmotic
balance exist; perhaps they are old (or young?) corpuscles. In
anemias the presence of many cups has been reported (Quincke,
"77; Grawitz, 799) and in fevers it is said crenation may occur
THE AMERICAN JOURNAL OF ANATOMY, VOL. 22, No. 3
470 LESLIE B. AREY
(Grawitz, ’02). Experimentation with diluting media at the
critical concentrations which first produce the cups from discs,
or which cause laking and crenation, makes it certain that there
is considerable variability in the responsiveness of individual cor-
puscles. Weidenreich (’02) further notes that there is a limited
variation in different individuals, and Lackschewitz (’92) and —
Hamburger (’02) have compared the unequal resistance of the
corpuscles in certain of the lower animals.
May it be that the blood of certain individuals contains nor-
mally excessive numbers of cup-shaped corpuscles? Is it pos-
sible that this explains why some of our most careful workers
have been led to describe this form as normal?
The teachings of comparative histology do not support the
cup shape; but it may be objected that the loss of the nucleus
among mammals is in itself directly or indirectly responsible for
the assumption of the cup shape (ef. Rindfleisch, et al.). In
this connection might be mentioned Howell’s (00) statement .
that biconcavity is a physical advantage because the absorbtive
surface is increased, and the conclusion of Rice (’14) that the
biconcave form is physically the ‘best’ since it is one having
less surface energy than any surface obtained from it by a small
deformation consistent with constant volume.
It is conceivable that the action of hypotonic solutions in
swelling corpuscles assymetrically is associated with the loss of
the nucleus. Whether the side through which the nucleus is
expelled becomes more elastic (weakened) or less elastic (Le.,
like sear tissue) is, however, pure conjecture.
E. SUMMARY
The shape of the mammalian red blood corpuscle depends
largely on the osmotic pressure of the examining medium. In
solutions corresponding to ca. 0.9 per cent sodium chloride the
erythroplastid possesses a biconcave form. In_ progressively
less concentrated (hypotonic) solutions water is imbibed and
the corpuscles swell to thin-walled cups, thick-walied cups,
dimpled spheres, and finally lake forming ‘shadows.’ In hyper-
tonic media crenation results.
SHAPE OF MAMMALIAN RED BLOOD CORPUSCLE 471
Between the limits of form induced by a 0.3 per cent sodium
chloride solution and by mild: crenation the shape of the red
corpuscles is repeatedly reversible.
Individual variability exists in the response of erythroplastids
to diluting media; this is perhaps referable to diverse elastici-
ties of the corpuscular membranes.
Undiluted drawn blood, and blood diluted with human serum,
show the red corpuscles to be biconcave discs. Human serum
must be diluted about one-third with water before the cup form
predominates.
Freezing point determinations which show that mammalian
plasma is isotonic with a 0.9 per cent saline solution (instead
of 0.6 per cent) are roughly substantiated by such dilution
experiments.
The study of circulatihg blood in non-anesthetized living
mammals corroborates the normality of the disc.
The results gained by the use of fixatives, although seemingly
adverse to the disc view, may be satisfactorily interpreted in
terms of unequal fixation; this is supported by experiment.
The several lines of evidence here presented seem to justify the
conclusion that the biconcave disc represents the normal shape of
the mammalian erythroplastid—the concavo-convex cup being merely
an occasional modification.
F! BIBLIOGRAPHY
Ausrecut, E. 1904 Cytopathologische Mitteilungen. Verhandl. d. deutsch.
Pathol. Gesell. Jahrg., Heft 1, pp. 88-94.
Arey, L. B. 1916 The mammalian erythrocyte—a biconeave disc. Science,
n.s., vol. 44, no. 1138, pp. 392-395.
Brass, A. 1897 Atlas of human histology. Trans. by R. A. Young. Wm.
Wood and Company, New York, 160 pp.
v. Davin, C. 1908 Ueber optische Einstellungsbilder kreisscheibenférmiger
Erythrozyten. Arch. f. mikr. Anat., Bd. 71, pp. 159-163.
Dexkuuyzen, M. C. 1899 Becherférmige rote Blutkérperchen (‘Chromokra-
teren’). Anat. Anz., Bd. 15, no. 11 und 12, pp. 206-212.
1901 Uber die Thrombocyten (Blutplittchen). Anat. Anz., Bd. 19,
no. 21, pp. 529-540.
DusgarpviIn, F. 1842 Nouveau manuel de |l’observateur au microscope. Li-
brairie encyclopidique de Roret, Paris. 330 pp.
von Exsner, V. 1902 Vom Gefisssystem. Koelliker’s Handb. d. Gewebelehre
d. Menschen. Englemann, Leipsig. Bd. 3, 1020 pp.
472 LESLIE B. AREY
Ecxer, A. 1851-99 Icones physiologic. Voss, Leipzig. 48 pp.
Fontana, F. 1787 Abhandlung tiber das Viperngift u. s. w. Ch. Himburg,
Berlin, 11 + 500 pp.
Fucus, H. 1903 Uber die sogenannte ‘‘intracellular’’? Entstehung der roten
Blutkérperchen junger-und erwachsener Siuger. Anat. Hefte, Bd. 22,
Heft 1, pp. 95-136.
Funke, O. 1853 Atlas of physiological chemistry. Cavendish Soc. Works,
London, 29 pp.
Gacar, 8S. H. 1888 The form and size of the red blood corpuscles of the adult
and larval lamprey eels of Cayuga Lake. Proc. Amer. Soc. of Micros-
copists, vol. 10, pp. 77-83. .
Giacuio-Tos, E.* 1899 A proposito dei Cromocrateri nel sangue della Lam-
preda. Anat. Anz. Bd. 15, no. 16, pp. 298-300.
Grawirz, E. 1899 Ueber kérnige Degeneration der roten Blutkérperchen.
Deutsche med. Wochenschr. Jahrg. 25, no. 36, pp. 585-587.
1902 Klinische Pathologie des Blutes u. s. w. G. Thieme, Leipsig,
2te Auflage, 796 pp.
Hampuracer, J. H. 1902 Osmotischer Druck und Ionenlehre in den medizin-
ischen Wissenschaften. Bergmann,«Wiesbaden, Bd. I. 13 + 539 pp.
HEIDENHAIN, M. 1904 Ueber die Oberflichenkrifte als Ursache der sogen.
‘“Geldrollenform”’ der roten Blutkérperchen und verwandte Erschei-
nungen. Folia haematol., Jahrg., no. 8, pp. 461-475.
Hetnz, R. 1890 Arbeiten aus dem pharmakolog. Institut der Univ. Breslau.
1. Die Wirkung konzentr. Satzlosungen. 2. Morphologische Verin-
derungen der roten Blutkérperchen durch Gifte. Arch. f. path.
Anat. u. Physiol. u. fur klin. Med., Bd. 22, Heft 1, pp. 100-116.
1901 Uber Blut-Degeneration und Regeneration. Beitrage z. path.
Anat. u. zur allgem. Path., Bd. 29, pp. 299-404.
HENLE, J. 1841 Allgemeine Anatomie. Voss, Leipsig. 23+ 1048 pp.
Hewson, W. 1777 The Works of William Hewson. London (1846). 56+ 360
pp. ;
Hoéper, R. 1902 Physikalische Chemie. Der Zelle und der Gewebe. Engle-
mann, Leipsig, 12 + 344 pp.
Howeti, W. H. 1900 The life-history of the formed elements of the blood,
especially the red blood corpuscles. Jour. Morph., vol. 4, no. 1, pp.
57-130.
Hogan, J. J. 1915 The intravenous use of colloidal (gelatin) solutions in
shock. Jour. Amer. Med. Assn., vol. 64, pp. 721-726.
Jotuy, J. 1904 Sur la forme des globules rouges & propos des communications
de M. Triolo. Comp. rend. soc. Biol., T. 57, no. 2, pp. 339-3842.
1905 Sur la forme des globules rouges des Mammiféres. Comp.
rend. soc. Biol., T. 58, pp. 481-483.
1906 a Quelques remarques 4 propos de la forme, de la structure et
de la fixation des globules rouges des Mammiféres. Folia haematol.,
Jahrg. 3, no. 4, pp. 183-186.
1906 b Courte résponse & la note précédente de M. Weidenreich.
Folia haematol., Jahrg. 3, no. 5, p. 244.
SHAPE OF MAMMALIAN RED BLOOD CORPUSCLE A473
Jouuy, J. 1909 Sur quelques points de la morphologie du sang étudiés par
V’observation de la circulation dans l’aile de la chauve-souris. Arch.
d’Anat. microscopique. T. 11, pp. 94-109.
Jorpan, H. E. 1909 The shape of the red blood corpuscles. Anat. Anz., Bd.
34, no. 16 u. 17, pp. 406-412.
1915 The shape of the human red blood corpuscles. Proc. Soc. Exp.
Biol. and Med., vol. 12, no. 7, pp. 167-169.
Korprr, H. 1899 Die Volumensiinderungen rother Blutscheiben in Salzlés-
ungen. Arch. f. Anat. und Physiol., Physiol. Abt., Jahrg., pp.
504-517.
Lackscnewitz, T. 1892 Uber die wasseraufnahmefahigkeit der roten Blut-
kérperchen nebst einigin Analysen pathologsichen Blutes. Laak-
mann, Dorpat, 43 pp.
LEEUWENHOEK, A. 1719 Epistole physiologice. Beman, Delphis, 48 + 466
pp-
Lewis, F. T. 1904 The shape of mammalian red blood corpuscles. Jour. Med.
Research, vol. 10 (n. s. 5), no. 4, pp. 513-517.
1913 A text-book of histology. Blakiston, Phila., 11 + 539 pp.
Lirren, M. 1877 Ueber einige Verinderungen rother Blutkérperchen. Ber-
liner klin. Wochenschr. Jahrg. 14, no. 1, pp. 1-5.
Louner, L. 1907 Ueber einige neue Beobachtungen am Blute nach Einwir-
kung des elekrischen Entladungsschlages. Arch. f. d. gesam. Physiol.,
Bd. 120, pp. 193-204.
1910 Uber die Glockenformen von Siugererythrocyten und ihre
Ursachen. Arch. f. d. gesam. Physiol., Bd. 131, pp. 408-424.
1911 Ueber das Osmium tetroxyd als Blutfixationsmittel und die
Form der Siugererythrocyten. Arch. f. d. gesam. Physiol., Bd. 140,
pp. 92-108.
Mauassez, M. L. 1896 Sur les prétendus liquides conservateurs ou fixateurs
des globules rouges, et les erreurs qu’ils peuvent causer dans les men-
surations et évaluations de volume de ces éléments. Compt. rend.
soc. Biol., T. 48, p. 511-514.
Minot, C. 8. 1912 Keibel and Mall, Manual of Human Embryology, vol. 2,
Lippincott, Phila., 8 + 1032 pp.
Miter, J. 1832 Beobachtungen zur Analyse der Lymphe, des Blutes und des
Chylus. Annalen d. Physik u. Chemie, Bd. 25, pp. 513-590.
Moys, W. W. 1738 De carnis musculose, etc. Langera, Bat., 431 pp.
1851 Musculorum artificosa fabrieca ete. Bonk et Becker, Bat., 431
pp.
Orsés, F. 1909 Ueber die Form und die Formverinderungen der bikonkaven
roten Blutkérperchen. Folia haematol., Bd. 7, Heft 1, pp. 1-18.
Prevost, J. L. er Dumas, J. A. 1821 Examen du sfng e’ de son action dans
les divers phenomenes de la vie. Biblioth. univers. des sc. b. 1. et a.
Geneve, 24 pp.
Quincke, N. 1877 Weitere Beobachtungen iiber perniziose Animie. Deutsch.
Arch. f. klin. Mediz. Bd. 20, pp. 1-31. ~
Ravascu, H. E. 1906 Ein Beitrag zur Gestalt des roten Blutkérperchens beim
Menschen. Anat. Anz., Bd. 28, no. 23, pp. 600-604.
Ranvier, L. 1875 Traité technique d’Histologie. 2d ed., Paris, 871 pp.
474. LESLIE B. AREY
Ricr, J. 1914 Note on the form assumed by the red blood corpuscles of the
blood, or by the suspended particles inalecithin emulsion. Philosoph.
Mag., vol. 28, pp. 664-670.
Rinprueiscu, G. E. 1880 Ueber Knochenmark und Blutbildung, II, III.
Arch. f. mikr. Anat., Bd. 17, pp. 21-42.
Scudrer, E. A. 1912 Quain’s Anatomy, Vol. 2, Pt. 1; 11th ed., Longmans
Green & Co., London, 11 + 739 pp.
Scuutrz, C. H. 18386 Das System der Circulation, u. s. w. Cotta, Stuttgart
u. Tiibingen, 368 pp.
Scuuttze, M. 1865 Ein heizbarer Objekttisch und seiner Verwendung bei
Untersuchungen des Blutes. Arch. f. mikr. Anat., Bd. 1, pp. 1-42.
DE SENAC, J. B.. 1749 Traite de la structure du Coeur, etc. Vincent, Paris, T.
2, 504 pp.
Sréur, P. 1906 Lehrbuch der Histology und der mikroscopischen Anatomie des
Menschen. 12th ed., Fischer, Jena, 15 + 464 pp.
Trroto, M. 1904a Nouvelle recherches experimentales sur la morphologie des
éléments figurés du sang. Camp. rend. soc. Biol., T. 57, no. 145, pp.
292-293.
1904 b Examen du Sang humain in vitro par le methode de la ‘lubri-
fication’ (Méthode a l’huile de vaseline). Comp. rend. soc. biol., T.
57, pp. 307-809.
1905 Nuove ricerche sperimentali sulla morphologia degli elementi
figurati del sangue. Gazzetta d. Osped. Milano, vol. 26, pp. 1534-
1536.
Wagner, R. 1833 Zur vergleichenden Physiologie des Blutes. Voss, Leipzig,
8+ 80 pp.
1838 Nachtrige zur vergleichenden Physiologie des Blutes.
Weser, E. erSoucHarp 1880 De ladispositionen piles qu’affectent les globules
rouges du sang. Arch. de Physiol., Année 1880, pp. 521-531.
WeipenreicH, F. 1902 Studien tiber das Blut und die blutbildenen und -zer-
storenden Organe. Arch. f. mikr. Anat. Bd. 61, pp. 459-507.
1903 Die roten Blutkérperchen. Ergeb. d. Anat. und Entwickl.,
Bd. 138, pp. 1-94.
1905 a Ueber die Form der Séugererythrocyten und die formbestim-
menden Ursachen. Folia haematol., Jahrg. 2, no. 2, pp. 95-104.
1905 b Einige Bemerkungen iiber die roten Blutkérperchen. Anat.
Anz., Bd. 27, no. 24, pp. 583-596.
1906 a Eine neue einfache Methode zur Darstellung vom Blut—
Trockenpriparaten. Folia haematol., Jahrg. 3, no. 1, pp. 1-7.
1906.b Studien iiber das Blut und die blutbildenen und -zerstérenden
Organe. IV. Weitere Mitteilungen iiber rote Blutkérperchen. Arch.
f. mikr. Aftat., Bd. 69, pp. 389-488.
1906 ec Einige Bemerkungen zu dem Aufsatze J. Jolly’s iiber die
Form, Strukture, und Fixation der roten Blutkérperchen der Sauge-
thiere. Folia haematol., Jahrg. 3, no. 5, pp. 241-244.
1910 Uber die Form der Siugererythrocyten. Eine Erwiderung an
Dr. L. Léhner. Arch. f. d. gesam. Physiol., Bd. 132, pp. 148-146.
Youna, T.. 1813 An Introduction to Medical Literature, ete., Philips, London,
26 + 659 pp.
AUTHOR’S ABSTRACT OF THIS PAPER ISSUED
BY THE BIBLIOGRAPHIC SERVICE SEPTEMBER 28.
SEASONAL CHANGES IN THE INTERSTITIAL CELLS
OF THE TESTIS IN THE WOODCHUCK (MARMOTA
MONAX)
ANDREW T. RASMUSSEN
From the Department of Histology and Embryology, Cornell University, Ithaca,
New York
ONE CHART AND THREE PLATES (TWENTY-SIX FIGURES)
INTRODUCTION
It is generally accepted that there is a close relationship be-
tween the testis of male vertebrates and the development of the
genital tract and of the secondary sexual characters. There is a
further tendency to regard the testis as one of the endocrine or-
gans which elaborates some internal secretion which governs the
above mentioned growth processes and which plays some réle
in connection with the sexual instincts. Naturally many
workers along this line have attempted to ascertain what tissue
in the testis is responsible for the production of the ‘autacoid,’
if such there be. The extensive and comparatively recent re-
views of the literature by Biedl (Innere Sekretion, II Aufl., 13)
and by Tandler and Grosz (Die biologischen Grundlagen der
sekundiren Geschlechtscharaktere, Berlin, 713), as well as re-
searches reported since thesé works appeared, seem very con-
vincing that the interstitial cells (cells of Leydig), and not the
germinal cells nor Sertoli cells, are the producers of the internal
secretion. Hence the term ‘interstitial gland of the testis,’
first used by Bouin and Ancel in 1903, occurs quite frequently
in the literature of the present day. It must be admitted, how-
ever, that the Sertoli cells, especially, have not been adequately
ruled out as a possible factor in this endosecretory function.
475
476 ANDREW T. RASMUSSEN
Adding still more interest to this subject is the serious consid-
eration which it is receiving by clinicians.'. While during the
last few years, surgeons have performed a number of grafting
operations on men with some success, a rather unexpected re-
sult has been reported by Morris (16), who found that testic-
ular grafts caused an undeveloped testis to enlarge and become
apparently normal. This is mentioned here only because it
indicates the practical importance of advancing our knowledge
concerning the endocrine function of the testis.
Since all the evidence in favor of the secretory function of the
interstitial cells of the testis, as well as of the ovary, is indirect,
there are those who hesitate (c.f. Kingsbury, ’14, W. Blair Bell,
16) in ascribing to these cells the function of producing a spe-
cific substance of ‘hormonie’ or ‘chalonic’ action in the organism.
Bell is especially emphatic as may be seen from the following
quotation (p. 145): 2
Again, it is extremely interesting to note how erroneous has been
the view, generally held, that the interstitial cells of the ovary and
testis are responsible for the secondary sex characteristics. For many
years I have contended that the gonads play but a subservient part;
and this is emphatically demonstrated . . . . by the fact that
in the testes of tubular partial hermaphrodites with feminine secondary
characteristics, . . . . , the interstitial cells are always devel-
oped to a remarkable extent to a degree which is rarely seen even in
the undescended testis and never in the normal .testis. These cells
cannot, therefore, be responsible for the secondary characteristics.
The evidence supporting the secretory function of the inter-
stitial cells has been derived from various sources, the most
important of which are: the general histological character of
the interstitial cells (epithelioid); various pathological con-
ditions of the testis and abnormal sex development, such as
the various forms of hermaphrodism and cryptochism, with the
corresponding histological character of the tissues of the tes-
tis; effects of castration, vasectomy and transplantation in
man and laboratory animals; exposure of the testis to the influ-
ence of X-rays; injection of testicular extracts; degree of de-
1 See, for example, On abnormalities of the endocrine function of the gonads
in the male, Lewellys F. Barker, Amer. Journ. Med. Sci., 1915, vol. 149, p. 1.
SEASONAL CHANGES IN INTERSTITIAL CELLS 477
velopment of the interstitial cells at different periods of life
and the periodic changes which they undergo in adult animals
as related to the sexual cycle. This last line of evidence is
somewhat conflicting. It is, of course, difficult in most of
the higher animals, epecially domesticated ones, to correlate
the various phases of the spermatogenic cycle with changes
in the interstitial cells because the various progressive and
regressive changes in the tubuli contorti are going on more or
less side by side at the same time. For this reason Tandler
and Grosz (711) selected as material for a study of this question
an animal (mole) in which the interval between rutting periods
was sufficiently great to separate the stages in the spermatogenic
cycle, since this animal is sexually active only in the spring.
The woodchuck, which is abundant in many parts of the United
States and Canada and even Alaska (Howell, 715), similarly
should furnish facts of interest in this connection. This ani-
mal also is sexually active only in the spring. The female gives
birth to but one litter a year, the young being born about the
last part of April or the first of May, according to Merriam(’84) .
These dates agree well with the general life history of these
animals as observed in this vicinity. Merriam further states
that along the western border of the Adirondacks they go into
hibernation late in September and remain till the middle. or
last of March. In this region in their normal habitat they do
not retire till nearly a month later, and those kept in captivity
usually remain awake till the last of November. Probably those
that retire in natural burrows do not become actually dormant
till several weeks afterwards.
Incidentally the study reported here is of interest also in con-
nection with the subject of histological changes during inani-
tion—a subject having many important bearings upon growth,’
metabolism and physiological adaptation. All species of Ameri-
can marmots hibernate profoundly. ‘They store up no food, ex-
* This point is especially discussed by Sergius Morgulis, Arch. f. Entw. d.
Organ., 1911, vol. 32, p. 169. Here is also reviewed the literature on the effect
of experimental inanition on histological changes in the testis. This deals,
however, with spermatogenesis and not with the interstitial cells. The data
reported in this connection does not show very uniform results.
478 ANDREW T. RASMUSSEN
cept within their own bodies, and hence are deprived of food, in
the ordinary sense, for about four months out of each year.
This may thus be considered a long period of physiological in-
anition. During much of this time they are very dormant and
have the usual low body temperature (a few degrees above
0°C.), slow circulation and respiration, etc., characteristic of
hibernation.
HISTORICAL ;
While the interstitial cells were discovered in 1850 by Leydig,
the first report on changes in these cells either in connection
with the seasons of the year or with the sexual cycle of the
adult, did not appear till many years later when Hansemann
(95) reported that he had observed the testis of the marmot
and found that the testis of the hibernating animal, in which
there is no spermatogenesis, contains practically no inter-
stitial cells, there being only a few spindle-shaped cells be-
tween the tubules. After the animal has been awake for two
months, however, and spermatogenesis is going on, the inter-
stitial cells are very numerous, so much so that they give the
appearance of a sarcoma. He considered that these cells prob-
ably constitute an organ with some specific function.
Friedmann (’98) followed with an extensive study of the
more or less parallel development of the interstitial tissue and
the progress of the spermatogenic cycle in frogs (Rana fusca,
Rana viridis, Hyla arborea) and the toad (Bufo vulgaris). In
frogs he found an increase in the interstitial cells during the
progress of spermatogenesis as autumn approaches. Beginning
with the end of October with the cessation of spermatogenesis,
the interstitial cells almost disappear and remain minimal till
about’ May. An important point mentioned by Friedmann in
connection with Rana viridis is the observation that in the same
testis there may be a difference in the amount of interstitial
tissue. Where the spermatogenic process is most active, there
the interstitial cells are most developed. In the tree frog (Hyla
arborea) the interstitial cells seem to be about a month behind
in development in comparison with the brown and the green
frog.
SEASONAL CHANGES IN INTERSTITIAL CELLS 479
At the end of May the same condition prevails in the toad as
in the frog, there being only a few interstitial cells and mostly
spermatogonia in the tubules. As spermatogenesis advances,
there is a more or less parallel growth in the interstitial cells.
Active spermatogenesis continues on into the winter. Free sper-
matozoa are most numerous at the end of April at which time
the interstitial cells are maximal and loaded with fat, but con-
tain practically no pigment, as compared with the numerous
pigment granules present in the interstitial cells later in summer.
He also observed that the first fat to appean was not interstitial
but intratubular.
Ganfini (03) found that in the hibernating marmot the inter-
stitial cells are not fewer in number than during the active
period, as was reported by Hansemann, but are only smaller in
size and different in structure. They stain less readily and
as a whole give the appearance of a structure which has ceased
secreting. During winter-sleep they also assume a rounder
form. He does not think these changes have anything to do
with spermatogenesis, but are due rather to the same causes
that arrest the processes going on in the other organs. In this
animal he describes the interstitial cells as being arranged in
lobes and cords bounded by endothelium, but some are also
found isolated.
Regaud (’04) reported that spermatogenesis goes on ‘in the
mole (Talpa europaea) during autumn and winter. In Decem-
ber the tubules occupy most of the testis. The tubules, although
large, are separated from each other by wide spaces containing
only a few interstitial cells. By February the testis has become
more than 15 mm. in length. In June and July the interstitial
cells are voluminous, closely packed together and occupy more
space than the tubules. The cytoplasm of the interstitial cells
at this stage is greatly vacuolated. By July the testis has
decreased to only 3 or 4 mm. in length; but the interstitial cells _
still persist, giving the adult organ the appearance of a foetal
testis. Spermatogenesis has ceased and in the tubules there is
only a syneytium of Sertoli cells and a few spermatogonia.
Thus he considers these observations to be just the opposite
480 ANDREW T. RASMUSSEN
of those reported by Hansemann. Although the seasonal changes
were not followed out any farther, he concluded that the inter-
stitial cells do not degenerate parallel with the germinal epithe-
lium during the retrogressive changes in the spermatogenic cycle.
It is to be noted that in the mole the testes are abdominal
and situated beside the bladder in December; but with the in-
crease in size which occurs from January on and culminates in
March, the testes come to occupy two pouches beside the root of
the tail. Periodic changes in the size of testis are well known
in many species, having been observed as far back as the days
of Aristotle (Marshall, ’11). The tendency for the testes to
enlarge and also to descend into a sessile scrotum during rut
in most rodents was mentioned by Owen (’68) fifty years ago.
The general subject of the descent of the testis cannot be dis-
cussed here. The excellent papers by Hart (09) and Frankl
(00) present this subject most admirably.
Champy (’08) reported that in Rana esculenta spermato-
genesis is at its highest in July and at this time the intersti-
tial cells are at a minimum. In the autumn there is a great
increase in the interstitial cells and spermatogenesis is at its
lowest. This observation seems to be rather an exception to
what Friedmann and later Mazzetti report in other species of
frogs. However, in view of a lack of details, there may not be
as much disagreement as the bare statement above would indicate
at first sight, the breeding season being about two months later.
Lécaillon (’09) in general confirms the observations of Regaud
on the mole both in regard to the change in size of the testis
and the relation of interstitial cell development to spermato-
genesis. He claims, however, that in July there is much degen-
eration in the interstitial cells and that this is responsible for a
large part of the decrease in the size of the testis at this time; but
some of the interstitial cells persist throughout the entire year.
— Mazzetti (11) in working with frogs (Rana fusca and Rana
viridis) found the seasonal changes in the interstitial cells to
be essentially as had already been described by Friedmann.
He ‘incidentally states that interstitial cells are extraordinarily
abundant in hibernating snakes but not in the ‘ghiro.’
SEASONAL CHANGES IN INTERSTITIAL CELLS 481
Marshall (11), from a study of fourteen hedgehogs, found no
spermatogenesis in this animal during winter, at which time the
sexual organs are small. Beginning about the end of March,
shortly after the close of the hibernating period and at the
approach of the rutting season, these organs enlarge, reaching
complete development in May. Spermatogenesis is going on
simultaneously and by the end of April free sperms are recog-
nizable. The testis does not, however, enlarge to the same
extent as in the mole. \ While the increase in the size of the
testis is due in part to an increase in the spermatogenic tissue,
a greater factor in the growth of this organ is the proliferation
of interstitial cells, which leaves the tubules widely separated
from each other, especially in the central part of the testis.
Large blood vessels apparetnly also develop in this interstitial
tissue. This condition persists till October, after which retro-
gression sets in, the interstitial cells largely disappear and with
them the blood vessels Just mentioned. The tubules are thus
’ brought almost into contact and spermatogenesis is in abeyance.
There is little or no change till after hibernation when the
next rutting season begins. The female produces one litter in
May or June and another again in August or September. During
the period from about April till as late as October, the testes
are descended into sac-like continuations of the abdominal
cavity in the neighborhood of the perineum, where they may be
detected from the exterior. The author concludes that the simul-
taneous growth in the accessory generative organs, especially
noticeable in the case of the,seminal vesicles, is probably due to
an internal secretion elaborated by the interstitial cells during
their period of increase.
The most detailed description so far encountered in the lit-
erature on this subject is that given by Tandler and Grosz (’11)
who examined the testes of moles (Talpa europaea) sacrificed
at various times during more than two years so that every
month was represented in the ‘series. They concluded that
rutting goes on during the month of March at which time the
testis has enlarged to about three times the usual diameter and
the tubules contain active spermatozoa. Similar changes occur
482 ANDREW T. RASMUSSEN
in the epididymis and other genitals. The increase in the
size of the testis is due to development of the generative part
of the organ. Interstitial cells are present only as small islands.
The cytoplasm of the individual cell is homogeneous. At the
end of March when most of the sperms are gone, the interstitial
cells are still only minimal in quantity. As summer approaches
the whole testis and the tubules decrease, reaching their lowest
in July. The interstitial cells, however, increase till their indi-
vidual boundaries are nearly obliterated. The cytoplasm stains
more brilliantly with eosin. The nucleus, on the other hand, re-
mains about the same size; but the chromatin is less evident. By
July the tubules are separated from each other by masses of in-
terstitial cells whose cytoplasm is greatly vacuolated and whose
nuclei have lost their definite nuclear structure. From the end
of September and on, spermatogenesis advances again and the
interstitial cells slowly decrease so that by February, when
spermatozoa are nearly free, they are limited to a few scattered
individual cells. Thus when spermatogenesis is at its highest, *
the interstitial cells are at their lowest, and vice versa. This
latter condition the authors compare to the foetal type as did
Regaud. They think that the increased interstitial cell growth
which occurs at the low ebb of spermatogenesis, has something
to do with the coming spermatogenic cycle.
A few incidental statements made by Cushing and Goetsch
(15) may be referred to here, since the observations concern
the woodchuck. The authors examined the testis of a woodchuck
killed March 22, having been captured a few days previously
(March 17, 1913). Judging from the weight of the animal
(2360 grams), the testis (1 em. by 1.75 cm.) was enlarged as
compared with the testis during the autumn and winter. His-
tologically they found no spermatozoa but a few spermatids
and an abundance of interstitial cells. In another animal
killed January 12, 1914—an animal which they were not positive
had hibernated—the testis showed active stages of spermato-
genesis but no spermatozoa. The interstitial cells were abun-
dant, but no statement is made as to how the interstitial cells
compared with those of the first animal examined.
SEASONAL CHANGES IN INTERSTITIAL CELLS 483 -
The great variability in the correspondence between the
progressive stages in the sexual cycle and increased intersti-
tial cell growth evidently calls for more observations if this
line of evidence is to be utilized in the interpretation of the
internal secretory function of the interstitial cells of Leydig.
PRESENT INVESTIGATION
This report is based upon a study of the testes of thirty-five
male woodchucks which have been killed at various times
during the past four years. The series includes twenty-three
adult animals, one or more years old, some of which have been
sacrificed in each month of the year; six younger animals (sev-
eral months to nearly one year old), some of which were sexu-
ally mature when killed, and six animals which were from about
five weeks to several months old.
Most of the testes were removed before death while the ani-
mal was under an anaesthetic (usually ether). Some were
removed immediately after death and, in a few cases, several
hours after the animal was shot. In the early spring at the
critical period of the year when the rutting season commences
and when it is difficult to capture the animal alive, a number
were shot and brought to the laboratory and the testes taken
out. Such material was used as control for that taken from
animals kept in captivity in artificial burrows. While both
males and females were always together in captivity and while
the artificial burrows, as described elsewhere,*? are such that
practically normal conditions should prevail, it was found that
females kept as late as April were not pregnant. Since they did
not breed in captivity, normal controls taken directly from
their usual habitat were necessary. Such controls showed,
however, that the male sexual cycle was not interrupted, at
least as far as the histological picture and the descent and
growth of the testis are concerned.
Except in the first few cases, the gross weight of the animal,
the weight of the gastro-intestinal contents and urine and the
3 Rasmussen, A. T. 1915. Amer. Journ. Physiol., vol. 39, p. 23.
484. ANDREW T. RASMUSSEN
weight of each testis, were obtained. From this data the weight
of the testis as per cent of the reduced body weight (gross weight
minus gastro-intestinal contents and urine) was calculated. The
position of the testis was also recorded. In every case the
weight of each testis of the same animal was practically the
same.
From about one-fourth to one-eighth of one testis (depending
upon its size) was fixed for eight hours in Zenker’s fluid with the
acetic acid reduced to only four drops per 100 ec. A few whole
testes were also fixed in this solution and sectioned longitu-
dinally in order to see if the interstitial cells were equally dis-
tributed in the various regions of the testis at the different
seasons of the year. After washing in running water for an hour,
such issue was placed in 2 per cent potassium dichromate for
four and one-half days. After a second washing of two hours
in running water, it was dehydrated in the usual grades of alcohol
containing iodine, two hours with several changes being allowed
for each grade till 98 per cent was reached. Here only one
hour was allowed. From 98 per cent alcohol the tissue was
transferred to chloroform for one hour with several changes and
then to chloroform-paraffin for one hour, and finally to par-
affin (melting at 54°C.) for two hours or longer. The aim of this
rapid embedding was to preserve the lipoids. This technique
as well as the subsequent Weigert staining was recommended
by Kingsbury who has found it very useful in demonstrating
lipoids (Kingsbury, 711). The fixer was not sufficiently washed
out by this method so that it was necessary to leave the sec-
tions, after having been fixed on the slide, several hours in the
lower grades of alcohol containing iodine before they were free
from precipitates.
This material was stained in ordinary hematoxylin and eosin,
iron hematoxylin, acid fuchsin and methyl green according
to the technique employed by Bensley (’11), but especially with
copper hematoxylin (Weigert’s), the older technique of differ-
entiating in the potassium ferricyanide and borax mixture
(diluted 3 to 10 times) being employed.
SEASONAL CHANGES IN INTERSTITIAL CELLS 485
Another part of a testis was fixed in Carnoy’s fluid (6: 3:1)
and stained with iron hematoxylin and also with Mayer’s
haemalum and eosin. |
A third and smaller section was fixed in Meves’ (’08) modifica-
tion of Benda’s fixer for four and one-half days both with and
without the subsequent pyroligneous-chromic acid and potassium
dichromate mordantage. This material was also dehydrated,
cleared and embedded rapidly according to the schedule described
for the modified Zenker’s material. It was stained. for mito-
chondria with sodium alizarinsulphonate and crystal violet ac-
cording to the technique employed by Meves and Duesberg (’08)
and also as used by Wildman (713). Sections were also mounted
unstained in balsam without any cover glass to demonstrate the
fatty globules which develop in the peripheral cytoplasm of the
interstitial cells and which are blackened by the osmic acid of
the fixer.
All sections were cut 4 » and 6 u thick. Those cut 4 u thick
were used almost entirely and comparable figures in the accom-
panying plates are from such sections.
On account of the large size of the testis, especially at certain
seasons of the year, and the soft consistency of the structures
within the tough tunica albuginea, it is difficult to get small
pieces, even with the sharpest razor, for fixers that penetrate
poorly, without disturbing the relationship of the interstitial
tissue to the tubules. As a consequence the osmiec acid stained
preparations used to demonstrate the fatty globules in the
peripheral cytoplasm of the interstitial cells, had to be taken
near the cut surface of the block where such disturbance had
occurred to a greater or less degree.
There is a strong tendency for the interstitial tissue to draw
away from the tubules in material fixed in both Carnoy’s and
Zenker’s fluid. This is especially true at certain seasons when
the interstitial tissue is very loose. The heat of the paraffin
bath may also have contributed to these artifacts. These de-
fects, however, serve to bring out even more clearly the relative
interstitial cell development at the various seasons and do not
invalidate the cytological details.
THE AMERICAN JOURNAL OF ANATOMY, VOL. 22, NO. 3
486 ANDREW T. RASMUSSEN
RESULTS
In late August, September and October the testes of the adult
woodchuek are minimal in size, being only 0.015 per cent to 0.020
per cent of the reduced body weight. They are abdominal, oc-
cupying a variable position in the dorsal portion of the abdom-
inal cavity on a level usually with the upper two sacral verte-
brae. They are a chocolate brown in color, due to a dark yellow
pigment found in the interstitial cells. The relative amount of
interstitial tissue may be judged from figure 1, which, however, -
is taken from an animal killed much later in the year. This
tissue is so loose that if an entire testis is placed in Carnoy’s
fluid the organ collapses from the absorption of the lymph faster
than the fixer enters the dense connective tissue tunica. It
consists of a fine connective tissue framework in which, be-
sides the usual fixed connective tissue nuclei, blood and lymph
vessels, etc., there are found a number of interstitial cells of
Leydig varying in size from small cells about 5 » in diameter,
with practically no cytoplasm and a more or less vesicular nu-
cleus, to larger cells about 10 uw in average diameter, with a
fair quantity of cytoplasm usually containing pigment granules,
which are slightly more numerous early in this period than later.
The nuclei of some of the smaller cells may be somewhat irregu-
lar or slightly spindle shaped and resemble the fixed connective
tissue nuclei. Indeed it is practically certain from the investi-
gations upon the origin of these cells that they are of connec-
tive tissue origin, and it is not improbable that they may re-
turn to this type again. The nucleus, however, of most of these
interstitial cells has the oft-described spherical and vesicular
appearance containing one nucleolus and a chromatin network
which ‘is especially coarse next to the nuclear membrane. The
cytoplasm varies greatly in amount, although it is always scanty
at this stage and gives a variety of irregular shapes to the cells,
as may be seen from figure 2 and the smaller cells in figure 3.
In nearly all these cells there are a variable number of the
small brown or dark yellow pigment granules. These, while
undoubtedly derived from the very labile lipoid or fatty glob-
SEASONAL CHANGES IN INTERSTITIAL CELLS 487
ules which once developed in the peripheral cytoplasm, as will
be indicated later, are preserved even in Carnoy’s fluid and after
such fixation are stained black with iron hematoxylin. This pig-
ment is darkened with osmic acid, but is not stained with ordinary
hematoxylin or eosin. The granules are usually aggregated at
one side of the nucleus, which is then somewhat eccentric, as
may be seen in figure 2.
In the material fixed in the modified Zenker’s fluid and
stained with copper hematoxylin, there appear to be a few other
granules in the cytoplasm. ‘These vary greatly in size from
very small ones about the size of mitochondria to larger ones
of the size of the pigment granules. From their staining reac-
tion and the fact that they are not always preserved by the
above method but show as small vacuoles in the dense cyto-
plasm at certain stages, and especially so after Carnoy’s fixer,
they undoubtedly contain a lipoid moiety. The only thing of
a mitochondrial character that could be demonstrated in the
interstitial cells at any period were these fine granules which
were most clearly shown with copper hematoxylin. However,
this point needs further investigation with different and more
carefully conducted technique, as a particular tissue may be
refractory to a particular technique even in the hands of ex-
perienced workers (c.f., e.g., Duesberg, ’17). Whitehead (’04,
05, ’08) has described granules in the cytoplasm of these cells
in the testis of the pig and other animals, which he finally
concludes (12) are a combination of protein and fatty material
and somewhat of the nature of mitochondria though differing
from the latter in certain staining reactions and in size, generally
being larger. He questions the presence of mitochondria as spe-
cific granules in the interstitial cells of the testis. Granules,
probably of a similar nature, are mentioned by other authors
(Regaud, ’01, Hanes, 711). The correspondence or identity of
these granules with the ones described here in the woodchuck
ean not be stated at this time, since this would involve special
work of a microchemicai nature, which was not anticipated when
this work was commenced.
488 ANDRBW T. RASMUSSEN
A few of the larger cells contain nearer the periphery of the
cell other fatty globules which are blackened by osmic acid,
and which are very much more soluble, disappearing even more
readily than the fat of ordinary adipose cells. These are the fatty-
granules so often found in these cells in animals generally.
In addition to the above described interstitial cells, which
for convenience will be spoken of hereafter as the ordinary type
of interstitial cells, there are scattered here and there, some-
times singly and sometimes in small groups, in the _ inter-
stitial tissue and quite frequently adhering to the basement
membrane of the tubules, a second type of Leydig cells. These
are much fewer in number but larger in size and contain large
pigmented granules to such an extent that the nucleus may
be crowded into an irregular space between the granules or to
one side of the cell. The nucleus is frequently irregular in
shape, in conformity to cytoplasmic pressure, and occasionally
gives the appearance of being in the process of degeneration.
A group of such cells is shown in figure 3 in connection with a
few interstitial cells of the ordinary type, which, as described
above, also contain pigment but in much smaller quantities
and as smaller granules. Occasionally the pigment granules
in these large cells, which may be spoken of as pigment cells,
are nearly as large as the nucleus (fig. 5). The presence of
so many large pigment granules may make the cell outline
very irregular, as may be seen in the upper left hand corner
of figure 2 where two cells of this kind are shown with the
pigment granules stained black thus obscuring the nucleus.
These larger pigment granules are evidently of the same com-
position as the smaller ones, staining black with copper hema-
toxylin and iron hematoxylin, at least on the surface, dark-
ened with osmic acid, also mostly on the surface, but not stained
with ordinary hematoxylin or eosin. Acid fuchsin may stain
some of them red.
~ Whitehead (08 a) in reporting on the eryptorchid testis of a
horse, describes cells of a similar character filled with a lipo-
chrome which had pushed to one side the nucleus, which was
small and pyknotic. He concluded that since there was a
SEASONAL CHANGES IN INTERSTITIAL CELLS 489
normal scrotal testis in this particular case, the abdominal one
was functionless as far as internal secretion is concerned, and
hence the interstitial cells of the eryptorchid testis had under-
gone a pigmentary degeneration. As will be disclosed later,
the origin of these cells in the woodchuck is undoubtedly of
this order, having resulted from the degeneration of some of
the ordinary interstitial cells when they undergo retrogression
in mid-summer, at which time the very soluble fat of the periph-
eral cytoplasm undergoes a radical change such that from these
fatty globules there is evolved a pigmented substance much
less soluble. Sehrt (04) considered the pigment usually found
in the interstitial cells as a lipochrome. These pigment cells as
well as the ordinary interstitial cells are distributed at all stages
about equally in all parts of the testis.
At this stage there are also a number of ordinary adipose cells
scattered through the interstitial tissue. Small fatty granules
are also found in the tubules, in fact at no time are the tubules
free from demonstrable fat which blackens with osmic acid
(figs. 14, 22, and 26).
Within the tubules early stages of spermatogenesis are in prog-
ress. The lumen is filling up with spermatocytes, which are
enlarging. No karyokinetic figures appear in them, however,
till about October.
The interstitial cell picture undergoes but little change till
after hibernation, or until early in March in these particular
animals. There is a slight gradual decrease in pigmentation
due to a disappearance of some of the pigment granules in the
ordinary interstitial cells and probably a slight decrease in the
number of pigment cells, which usually become smaller and
somewhat more irregular. The weight of the testis by Novem-
ber or December has increased to about 0.034 per cent of the
reduced body weight. This increase is evidently due to a fill-
ing up of the tubules with spermatocytes, for as seen in figure 1,
which especially represents this stage, the tubules are gorged
with spermatocytes showing open karyokinetic figures.
There is no sudden change in the testis with the onset of
hibernation as might be expected if the testis is an organ of
490 ANDREW T. RASMUSSEN
internal secretion, since at this time the bodily functions are
ereatly reduced and metabolism profoundly modified. However,
since the internal secretion of the testis has to do with the
reproductive side primarily, and not with the vegetative—
phases which may be more or less independent—it may not
necessarily follow that any marked observable change need be
registered in this organ at the beginning of or during this dor-
mant state. Certainly the interstitial cells in the woodchuck
remain practically unchanged during the hibernating period—
December, January, February. In the ground squirrel (Citellus
tridecemlineatus) which also hibernates, Mann (’16) reports
that the testis, while undergoing definite seasonal variations,
does not show any specific change due to the torpid condition.
At the beginning of March when the animal begins to awaken,
the tubules are-ready for a sudden and rapid production of sper-
matids and spermatozoa. The woodchuck may be semidormant
during this waking up period for several days and even longer.
During this sluggish period the changes in the testis commence,
so that before the animal has attained what may be termed its
homoiothermal temperature, changes in the testis have already
occurred. Figures 6 and 7 show these beginning changes in an
animal that is just waking up. In the peripheral cytoplasm of
the ordinary interstitial cells large fatty globules, which may
be blackened with osmic acid,-make their appearance and the
cells begin to round out. The testis now represents from
0.040 per cent to 0.050 per cent of the reduced body weight.
However, the animal has lost about one-third of its body weight
during the preceding months of inanition, consequently this rela-
tive weight of the testis is much exaggerated.
In the newly awakened and active animal the testis in-
creases very rapidly. The interstitial spaces become crowded
with enlarging interstitial cells of the ordinary type as is seen in
figure 11. In cells which have been fixed in Carnoy’s fluid, the
cytoplasm is greatly vacuolated (fig. 12) due to the fixer having
dissolved the fat. Figure 14 gives an idea of the relative amount
of fatty material at this stage. The fat is here blackened with
osmic acid.
SEASONAL CHANGES IN INTERSTITIAL CELLS 491
The denser cytoplasm around and to one side of the nucleus
expands, spreading out the pigment granules (fig. 12). Vari-
ous stages of this expansion are well shown in figure 13. This
figure in comparison with figure 12 shows also that there is in this
newly formed dense cytoplasm a number of the fine non-pig-
ment granules, characteristically associated with the central
cytoplasm (endoplasm), as mentioned above.
During this interstitial cell development there is no direct
evidence of mitotic or of amitotic cell division. Whitehead
(04) in describing the rapid growth in the size of these cells,
as it occurs in pigs from 20 to 28 em. in size, remarks that
there is no evidence of cell division after the 7 em. stage. This
early cessation of signs of division in the interstitial cells of the
testis seems to have drawn the attention of many investiga-
tors. Allen (’04) found, for example, no evidence of cell division
after the 7.5 cm. stage in the pig, nor after eight days after
birth of the rabbit. Plato (96), Finotti (97) and Kasai (’08)
comment on the absence of mitosis in the interstitial tissue of the
- human testis. Kasai in 130 human testes, representing the wide
range from the four months foetus to eighty-four years, saw only
one mitotic figure in the interstitial cells. However, in the
woodchuck at this stage of rapid interstitial cell growth, such.
stages as are shown in figure 8 are not uncommon. Later
when the cells reach their maximal size, one occasionally finds
cells evidently containing two nuclei as shown in figure9. In 4
out of 8 cases where the cells had reached their largest size, or
nearly so, the cells were arranged more or less in groups within
what appears to be a common membrane, such as is seen in figure:
10. This would suggest that there is cell division and that
each group of cells represents the daughter cells of a single
parent cell. Von Bardeleben (’97), while not seeing any mitotic
figures in the interstitial cells of executed criminals, frequently
saw evidences of direct cell division. Von Hansemann (95),
Reinke (96), von Lenhossék (’97) and Pick (’05), however,
have reported mitotic figures in human materials, including
adult.
492 ANDREW T. RASMUSSEN
A comparison of the number of nuclei appearing in a cross
section of the entire testis before enlargement sets in, with
nearly twice the number of nuclei seen when these cells are at
their maximal development (i.e., when the testis is fully twice
its former diameter) indicates that there is an increase in the
number of interstitial cells at this time in the adult wood-
chuck. It is necessary to make the comparison in this way since
the testis, having doubled in diameter, will during the highly
developed stage give twice as many sections as when small.
If the cells have not changed in number, only half as many
nuclei will appear in a section of a given thickness in case of the
large testis as in the case of the small one, provided the nucleus
has not also changed in size, since the same number of nuclei
would in the enlarged testis be distributed in twice as many
sections. But in reality the nucleus has increased about 1.5 u,
or 30 per cent, in diameter. While this is much less in propor-
tion to the inerease (more than 100 per cent) in the diameter
of the whole testis, it is sufficient to call for some allowance.
By counting the number of nuclei in numerous groups of inter-
stitial cells resulting from the arrangement of the tubules in
the reduced testis, and comparing this with the number of nuclei
found in the same number of groups in the enlarged testis, it |
appears that there are at least as many nuclei in a whole cross-
section of the hypertrophied testis as in a cross-section of the
testis before growth takes place. Making due allowance for the
increase in the size of the nucleus, the indications are that there
is a distinct increase in the interstitial cells of the hypertro-
phied testis. The assumption is that since there are as many
tubules intersected in the enlarged testis as in the small one
(as will be shown later in this paper), therr will be as many
cell groups confined between them.
Further evidence also appears from the number of nuclei seen
in a section of the testis that has just undergone retrogression
such as will be described shortly. In such a testis the number
of nuclei appears to be distinctly greater than obtains in the
testis just before it enlarges (figs. 23 and 24). A larger num-
ber of animal at each stage with an actual count of the number
SEASONAL CHANGES IN INTERSTITIAL CELLS 493
of cells from serial sections of the testes at the various periods
of the year would, of course, be necessary to rule out individual
variations and to definitely prove that there is an increase
in the number of cells and what that increase in number
amounts to. The facts cited above, however, make it very
probable that in the adult woodchuck there is a considerable
increase also in the number of interstitial cells after waking
up from hibernation although there is no direct evidence of either
mitosis of or amitosis.
The pigment cells do not undergo any growth or increase in
number. On the contrary they appear very inert and gradually
decrease in prominence. :
Going hand in hand with this interstitial cell hypertrophy,
there is still further increase in the size of the testis and ‘a re-
newed activity in the tubules. The spermatocytes rapidly
change to spermatids and free spermatozoa are seen by the
last of March. The most active stage (when most spermatozoa
appear to be set free) in the spermatogenic process is reached
early in April, by which time the testes have descended into
sessile scrotal pouches beside the penis. Thus the renewed
activity in the testis anticipated by Cushing and Goetsch (15)
actually takes place; but their assumption that this might be
attributed to the influence of the functionally reactivated pars
anterior of the pituitary body, does not necessarily follow,
since there is nothing to show that the testes or other organs
of the body—all of which show this renewed activity upon
awakening of the animal from hibernation—are influenced
through the pituitary rather than that the pituitary in common
with the other organs is influenced by the factors responsible
for the general awakening; that is, the pituitary and the testes
‘may have been influenced by the same factors rather than the
latter by the former. Furthermore, it is not even certain that
the pituitary does always undergo the change reported by these’
authors and by Gemeli, for Mann (’16) found that in the thir-
teen-lined groundsquirrel such changes while occurring in some
animals did not in others, although the testis underwent a sea-
sonal change. Jackson (17) thinks it highly probable that
494 ANDREW T. RASMUSSEN
these changes described in the hypophysis during hibernation
are simply the effects of the chronic inanition involved since
he finds similar changes in the hypophysis of the albino rat
subjected to inanition and refeeding.
The interstitial cells do not reach their maximum develop-
ment until the last of April when spermatogenesis is at its lowest.
Although many free spermatozoa may remain in the tubules
as late as this, the epithelium has been reduced to a single layer
of cells and thus a wide empty lumen results. The new sper-
matogenic cycle may be considered to date from the last of April
or early May, since spermatogonia begin to increase from this
time on.
The interstitial cells remain at their height of development
until as late as July, or for at least two months after the end
of the corresponding spermatogenic cycle. These dates will,
of course, vary somewhat from year to year.
During this time when the interstitial cells are enormously
enlarged, from about April to June—a period during which
the testes usually are scrotal—the testis represents from 0.078
per cent to 0.132 per cent of the reduced body weight. The
tubules are forced far apart as will be seen in figure 15, or still
better in figure 19, which is at a lower magnification and is
intended to show an especially large compact node of highly ~
vacuolated interstitial cells at the point marked with a +. In
the center of this mass the boundaries of the individual cells
are not evident and so gives the appearance of numerous nuclei
entangled in an open network. Such nodules were found in two
of the eight cases representing this stage. Several smaller
areas of this sort may be encountered in a single cross section.
The vacuoles are filled in life with fatty globules.
As mentioned above, half of the woodchucks killed during .
this stage showed the ‘nest’ arrangement of many and in one
tase practically all of the interstitial cells as seen in figure
10. This grouping was first described by Nussbaum (’80) as
the typical arrangement. Each group of cells seems to be sur-
rounded by an epithelial sheath of flat cells and the individual
cell boundaries are very indistinct. Ganfini (03) states that
-
SEASONAL CHANGES IN INTERSTITIAL CELLS 495
in the European marmot many of the cells of Leydig are ar-
ranged in cell masses and in cords thus bounded by ‘endothe-
lium’; but some are also found isolated. Such an arrangement
as shown in figure 10 may or may not be present in the case
of the woodchuck. The columnar arrangement described by
Ganfini (’02) is not found here, though some of the cell groups
in the cases just described are somewhat elongated. White-
head (’08) does not find this group arrangement typical. In the
eat he found columns of cells among the tubuli recti.
Due to mutual compression, the interstitial cells at this stage
vary in shape, with an average diameter in general of 20 uw to
25 uw. A few cells may be found that are as small as 14 uw in
average diameter. The nucleus is more eccentric and slightly
larger, being now 6 uw to 7 w in diameter as compared with
about 5 « when the cells are minimal in size. The pigment
granules in these ordinary interstitial cells’ have decreased
ereatly and only now and then is a granule found as may be
seen from figure 16. This recalls the findings of Friedmann
(98) who noted that when the interstitial cells of the toad
contained much fatty material the pigment was greatly reduced
and when the fat disappeared, the pigment was abundant again.
The dense central mass of cytoplasm is conspicuous and
contains a vast number of the fine lipoid granules, some of which
are very small (fig. 17). As stated above, these granules are
not preserved in Carnoy’s fluid and hence ‘appear as_ small
vacuoles in the dense central cytoplasm in figure 16 (seen best
in the cell marked with a+). The peripheral cytoplasm is
densely packed with the large fatty granules as indicated in
figure 18, especially in the insert where three cells are photo-
graphed under higher magnification.
A few of the pigment cells are seen here and there. Some
are very much reduced in size and are very irregular in out-
line, but others are well preserved. In one case the testis
was practically free from pigment either as smadl granules in
the ordinary interstitial cells or as larger spherules filling pigment
cells. As a result the testis at this stage is much lighter in
color than at any other time. ;
496 ANDREW T. RASMUSSEN
In mid-summer the testis again decreases. Figures 20, 21
and 22 show the conditions during the earlier stages of the
retrogression. In the particular case from which these figures
were taken, the testis represented only 0.038 per cent of the
reduced body weight, much of the fat already having been
absorbed, as is evident from figure 22 which is to be compared
directly ,with figure 18. The fat which is left is found as rather
large globules only a few of which are found in one cell as com-
pared with the numerous globules present earlier. During
this atrophy the interstitial cells are undergoing profound
modifications. Pigment granules are increasing due to a chemi-
cal transformation of some of the fatty material into a pigmented
compound. A number of the ordinary interstitial cells do not
decrease much in size but all the fatty globules within them
become changed to this pigment.
Spermatogenesis is steadily advancing. Spermatocytes are
increasing in number and are filling up the lumen of the tubules.
The testis becomes abdominal.
By August the testis is minimal, being only 0.015 per cent of
the reduced body weight. The tubules are much closer together
(fig. 23). Most of the interstitial cells are reduced to little
more than the nuclei, which have also become smaller, many
being under 5 » in diameter. Some of the smaller nuclei tend
to stain more solidly, due undoubtedly, as suggested by White-
head (’08), to a lack of decolorization. Plato (96) and Ganfini
(02) observed that the nuclei of the nonvacuolated cells appear
to stain more intensely than do those of the vacuolated ones.
Surrounding one-half of the nucleus there is in the scanty cyto-
plasm a dense cap of pigment granules as shown in figure 24.
If there are any of the finer lipoid granules, such as occupied the
dense central mass of cytoplasm before the atrophy occurred,
they are masked by the numerous pigment granules. The fatty
globules which filled the peripheral cytoplasm of the enlarged
interstitial cells have disappeared entirely (fig. 26).
A number of the cells have not undergone much change in
size. In figure 26 they are seen as the larger célls with coarse
spherical granules of various sizes within them. A group of
SEASONAL CHANGES IN INTERSTITIAL CELLS 497
such cells under higher magnification and as affected by the
osmic acid of Meves’ fixer, is shown in figure 25. The large
pigment globules have evidently been derived from the fatty
material with which these cells previously were filled. These
large pigment cells are most numerous just at the close of
these retrogressive changes. The pressure having been relieved
by the enormous decrease in the size of the other cells, these
pigment cells are more or less spherical at this stage. Osmic
acid still darkens the granules, at least on the surface; but they
are very insoluble, being preserved fairly well even in Carnoy’s
fluid as will be seen in figure 4, which also shows that from the
very first the nucleus may be irregular, which is most often the
case, though it may in some instances be apparently normal and
vesicular as in figure 5. Figure 5 is taken from a section which
passes through the cell near the middle plane and indicates that
the now-pigmented globules may still retain their peripheral
arrangement, leaving a less pigmented area'in the center. This
possibly represents somewhat of an intermediate stage in the for-
mation of the more solid and irregular pigment cells. Here then
we evidently see the source of the pigment cells that have been
followed through the preceding stages. The interpretation that
they originate from ordinary interstitial cells which undergo a
special pigmentary degeneration at the time when the rest of the
cells lose their fat and become small, is borne out by the absence
of these pigment cells in woodchucks that are less than one
vear old and have not passed through this adult retrogression
of the interstitial cells. No pigment granules are found in any
of the interstitial cells of the twelve animals less than a year
old. Fatty granules which are blackened with osmic acid are
however present in small quantities in the scanty cytoplasm of
some of the interstitial cells of these young animals. Thus a
new crop of pigment is produced once a year as fine granules
within the ordinary interstitial cells and as larger granules
which fill more or less completely certain other interstitial
cells, which as a result do not at this time decrease much in
size but remain as large pigmented cells for many months or
even a year and perhaps a few survive even longer, though ap-
498 ANDREW T. RASMUSSEN
parently most of them disappear by the end of the next period of
hypertrophy.
The origin of the pigment in the interstitial cells has been
debated. Von Hansemann (’95) considered that’ it was not due
to pigmentary degeneration, but rather that it is an infiltration
from some other source, since the pigmented cells are the larger.
Kasai (’08), however, states that in the human testis the pig-
mented cells are not especially larger and that it is the younger
cells that are not pigmented. Pigmentation, according to the
latter author, commences in the human testis first at 21 years
of age. With the advance of years and especially in old age
the pigmentation increases. These facts Kasai took to indicate
that it is a pigmentary degeneration—a view fully supported
by this work on the woodchuck. Whitehead (’08) believes
that the large pigment-laden cells which he observed in a case
of eryptorchism are due to pigmentary degeneration of ordinary
interstitial cells which in the retained testis have become use-
less—there being a normal scrotal testis to supply the necessary
internal secretion.
During this disintegration of the interstitial cells there is a
great increase in the number of ordinary adipose cells, which
are present in the testis at all times of the year. Fatty degen-
eration within the tubules is also seen at this time; in fact, fatty
globules are demonstrable in the germinal epithelium at all
seasons.
During all this time spermatogenesis is slowly progressing.
The diameter of the tubules changes but little during the entire
year. . They are probably somewhat smaller later in July, August,
and September and larger in November and December. How-
ever, the extremes in size may be encountered at other periods of
the year and the limited number of animals representing any one
period makes a- definite statement impossible. The rather
marked variation in the diameter of the tubules included in the
general views of the testis in the figures accompanying this paper,
is not representative. It happened that in selecting places to
show the relative amount of interstitial tissue the tubules were
not carefully observed as to size, as was evident from a compari-
SEASONAL CHANGES IN INTERSTITIAL CELLS 499
son of the pictures side by side. To check this point the diame- |
ter of a large number of tubules were measured with a filar ocular
micrometer with the results stated above. However, there is a
ereat difference in the degree to which the tubules are filled
with germinative cells. The open lumen seen during April and
May is now filling up with spermatogonia.
Cross and longitudinal sections of the testis rather indi-
cate that the tubules are merely separated farther from each
other when the interstitial cells are greatly developed. No data
is available as to the length of the tubules. Reconstructions
from serial sections would undoubtedly be necessary to show what
changes, if any, occur in this regard. There is no evidence of
any atrophy of the tubules as a whole at this or any other
period. The number of cross sections of tubules encountered in
a complete cross section of the entire testis near the middle,
just after the testis has been reduced in size, was about 850
as compared with about 1000 when the testis is maximal in size.
In six animals with testes at a minimum the number of times
tubules were cut in a complete cross section varied from about
750 to about 900 with an average of about 850; while in six
others with testes maximal in size the number varied from 900
to 1100 with an average of about 1000. Since the testis enlarges
from growth within, which undoubtedly increases the pressure,
the testis is more nearly round at this time than when it is
minimal. The transverse diameter is therefore relatively greater
and this may explain this difference. On account of the shape
of the tubules these figures are probably of very little value.
Since there is no sudden change in the tubules at the time
when the testis rapidly diminishes in size, the decrease must be
due to the atrophy of the interstitial cells, first in size and then
more slowly in number.
At no time was there any evidence of the crystalloids, first
described by Reinke (’96) in the human testis as passing from the
interstitial cells into the lymph vessels. While many subsequent
writers have seen these crystals. in the human testis, their
passage into the lymph vessels has not been confirmed. It
appears that these crystals have been found to any extent only
500 ANDREW T. RASMUSSEN
in the human testis. Neither is there any special relation
between the blood vessels and the interstitial cells such as
was first reported by Boll (’71) as being the typical arrangement
in case of the rabbit, but which has not in general been sup-
ported by later investigators. When the interstitial cells have
enlarged so as to crowd the intertubular space, the capillaries
run between the interstitial cells, which of necessity must sur-
round the vessels with little or no connective tissue between the
capillary wall and the cells. But at other times when the inter-
stitial tissue is loose, they are not especially arranged about the
vessels.
DISCUSSION
In order to get at a single glance the essential points in regard
to the question at issue, the principal facts with the authority
for the same, has been placed together in the accompanying
chart. Occasionally a few incidental facts which are included
were not given by the specific authority. Thus the time of
hibernation has in some cases been added, as well as other
data deemed of interest. Only the approximate time intervals
are, of course, possible in such a chart, since these will vary
with the seasons and the localities. However, they are be-
lieved to be sufficiently accurate to give a proper setting for
the various phases of the cycle. The curves are not con-
structed upon any quantitative basis, since not sufficient data
are given to make that possible. The highest point of the curve
is intended to indicate merely the approximate time when either
spermatogenesis or the development of the interstitial cells,
as the case may be, is at its highest, according to:the author’s
statement of the case. When more than one investigator have
reported on the same animal and only slight variations exist in
the findings, the curves have been combined into one. Undoubt-
edly other observations on seasonal changes in the interstitial
cells of adult animals are recorded in the enormous literature
upon the testis, but these included in the table are all that were
found to be directly to the point, after a reasonable search through
available sources.
SEASONAL CHANGES IN INTERSTITIAL CELLS 501
It is clear from this summary that interstitial cell develop-
ment does not always run parallel with spermatogenesis. The
notable exceptions are the mole (giving precedence to the most
complete report by Tandler and Grosz) and the woodchuck.
In the latter case the interstitial cells suddenly undergo retro-
Curves of Seasonal Dimorphism of ‘Testis
——= Spermallogenesis; +++ =Inlerslifial Cells ; = Hibernation
ANIMAL WAN! FEB)(IAR| APR. TAY MUNE JULY | AUG\SEPT] OCT | NOW| DEC |AUTHORITY
| Oe . : FRIEDMANN
| Rana, viridis MAZZETTI
WA
| M \
|P| TREE FROG N FRIEDMANN
H Hyla arborea SS 1898
i
B .
l| | FROG INN CHAMPY
A Rana esculenta BCS 1908
'N
5 S WN SIS 1
Rs ae RW
TOAD = SS) FRIEDMANN
Bufo vulgaris SSN TERR 1898
REGAUD
, 1904
LECAILLON
MOLE 1909
Talpa europea _
| Ie eRe i a ae TANDLER
\| Testis esi Testis and
M Peal onal SNe ae
V4
M N Testis lin Perineal [Pouch NS
he ee G spe SS MARSHALL
| Erinaceus europeus|\<S =\E ele \ 1911
A SS al’ ae
f | 3
9) marmot mine NOE RIAAN
| Marmota marmola & 35 GANFINI
bale 1905
|
ORR Testlis=.079| te, 132% Bw. = fH 7 SWS
| | woopcrucn [28") : ero) 1 RASMUSSEN
| Marmota monax [S : 2 TS 1917
[] Testis |So JSRSS.
THE AMERICAN JOURNAL OF ANATOMY, VOL. 22, NO. 3
502 ANDREW T. RASMUSSEN
eression while spermatogenesis goes on uninterruptedly. The in-
terstitial cells remain apparently inactive and greatly reduced
for many months while spermatogenesis goes on progressively.
It is only towards the last phases of spermatogenesis that the
interstitial cells show increased activity. This seems to be the
most striking correlation, namely, that the interstitial cells follow
wth renewed growth somewhat behind the spermatogenic cycle.
And in this sense it 1s conceivable that in the mole and Rena
esculenta the interstitial cells are only somewhat more than
usually behind.
The conclusion expressed by Allen (’04), that in the embry-
ology of these cells they develop with reference to degenera-
tion in the sex glands, is pertinent, although Whitehead (04)
did not confirm this point, claiming that the interstitial cells
appear before there are any signs of degeneration. Mazzetti
(11) explains their decrease in the frog in October as being due
to the fact that they have accomplished their purpose of absorb-
ing the useless testicular elements after intensive spermatogene-
sis. Kingsbury (14) emphasizes this point in connection with
the homologous cells of the ovary, where they are most numerous
about atretie follicles. In old men it appears well established,
especially from the extensive work of Spangaro (’01) and the
more recent examination of 130 human testes by Kasai (08),
that while there is usually a noticeable increase in the interstitial
cells at puberty, the number seems to decrease again during the
active sexual life of the individual to again increase with old age,
a time when there is more or less atrophy in the tubules. It is
certainly difficult to understand why this increased growth should
take place late in the spermatogenic cycle or with a cessation of
sexuality if this growth has anything to do with the production of
an internal secretion that is of importance in the development
of the genital tract, secondary sex characters or the sexual
instincts. It appears that in frogs (Rana fusca and Rana viridis)
spermatogenesis is initiated without any corresponding observ-
able change in the interstitial cells and when they are least active.
On the other hand in the woodchuck and mole the spermatogenic
cycle commences when the interstitial cells are well developed
or beginning to decline.
SEASONAL CHANGES IN INTERSTITIAL CELLS 503
The relation of the interstitial cells to the breeding period,
when copulation or fertilization takes place, is equally confusing,
since this period of sexual activity (spoken of as rutting in
many animals) may occur either when the interstitial cells
are showing evidence of increased activity (toad, hedgehog,
marmot (?), woodchuck) or when not noticeably changing
(frogs, mole). The descent of the testes may occur when the
interstitial cells are minimal (mole) or after these cells have
commenced to hypertrophy (woodchuck, hedgehog). In the
woodchuck they tend to remain scrotal while the interstitial
cells are enlarged. Here attention should be called to the ex-
periments of Harmes (13) in which he showed that the character-
istic thickening of the skin on the hands of the male frog during
the breeding season may be brought about through some in-
fluence exerted by Bidder’s organ alone in the absence of the
testis. This is true even when Bidder’s organ has been trans-
planted into the dorsal lymph sac, and Bidder’s organ contains no
interstitial cells. However, the testis alone in the absence of
Bidder’s organ can also cause this periodic thickening of the
skin.
The general functional reduction which takes place during
hibernation also applies variously to the interstitial cells. In
most of the hibernating animals they are quiescent during
dormancy, but in the toad they are developing. Nor is there
necessarily any marked change in their behavior at the onset of
torpidity as is also shown in the case of the toad, where they
go on increasing, and in the case of the woodchuck, where they
remain in the minimal stage to which they have been reduced
during the late summer preceding.
It thus appears that while the periodicity of the inter-
stitial cells would suggest some important function for them, it
is difficult to say what this function is specifically, because
of the lack of uniformity in their behavior. Granting that in
the main the observations here discussed are correct, one would
hesitate to use them as evidence of any weight in support of the
generally accepted idea that the interstitial cells of the testis
produce an internal secretion of specific importance to the sexual
life of the organism.
504 ANDREW T. RASMUSSEN
The réle of the large amount of fatty material which may
accumulate in these cells in certain animals—though rather
scarce in others, notably the pig—is of course equally obscure.
The chemical nature of the large globules in the interstitial
cells of the cat has been investigated especially by Whitehead
(12 b), who concluded that they are a mixture for the most part
of phosphatid lpoid but that cholesterinesters and neutral fats
are probably also present. The views that this lipoid is the
material out of which the internal secretion is made (Loisel ’02),
that it is the internal scretion (Ganfini, ’02), ete., need to be
supported by many more facts. The effects of lipoid extracts of
the testis, such as those reported by Iscovesco (138), are, of
course, very suggestive that the lipoid is an active agent.
In this connection we may recall the view of Plato (97), that
this fatty material passes through the walls of the tubules into
the Sertoli cells to be used as food for spermatogenesis. For
this reason he termed the interstitial cells ‘Trophische Hilf-
zellen.’ Lenhossék (97) entertained somewhat the same idea
and Regaud (’01) presented evidence of such a passage of sub-
stance from the interstitial cells to the Sertoli cells. Plato’s
idea was strictly opposed by Beissner (98) and in general this
passage of material through the walls of the tubules from the
interstitial cells has not been supported by the later investi-
gators. Friedmann (’98), however, suggested that the pigment
in summer and the fat in winter, in the case of the toad, es-
pecially, serve as the chief sources of nutrition for the proc-
esses going on in the tubules. Herxheimer concluded that in
individuals not yet sexually mature, the fat is mostly found in
the interstitial cells and is reserve material for the growing
testis, while in the sexually mature the fat is mostly found in the
tubuli contorti where it serves as reserve material for the de-
velopment of spermatozoa. Hanes (’11), however, associates
the fat storage with the Sertoli cells.
Of historical interest, at least, is also the conclusion of von
Bardeleben (’97) that the interstitial cells of the testis are
young Sertoli cells which can pass through the walls of the
tubules and replace worn out Sertoli cells. Goldmann (709),
SEASONAL CHANGES IN INTERSTITIAL CELLS 505
in fact, claims to have demonstrated such a passage of cells
into the tubules. Hanes (11), on the other hand, repeated
Goldmann’s vital staining method and could find no suggestion
of this migration of cells as described by Goldmann.
SUMMARY
1. In the woodchuck (Marmota monax) during late summer
and autumn, the interstitial cells of the testis are minimal
in size and probably reduced in number. The scanty cytoplasm
of these cells contains numerous pigment granules, some fine
lipoid granules, but only a very few of the cells contain the
coarser and more fat-like globules which are easily demon-
strable with osmic acid. There are a number of large inter-
stitial cells, which are gorged with prominent pigmented gran-
ules and which have resulted from a degeneration of some of
the other common and more numerous type of interstitial cells.
A new spermatogenic cycle is in progress. The testis is small,
dark in color and abdominal in position.
2. There is no sudden change in the interstitial cells with
the onset of hibernation and little or no change during dor-
mancy, except that there is a slight gradual decrease in pig-
mentation. Spermatogenesis remains much the same during the
torpid state as just before winter-sleep sets in. The tubules
are filled with spermatocytes showing open maturation figures
during the entire winter.
»o. In the spring as the animal is waking up from hiber-
nation, the interstitial cells rapidly enlarge and apparently
increase in number. The nucleus increases only slightly. The
great increase is primarily in the cytoplasm and is due to the
development of a dense central mass of cytoplasm and the
accumulation of fatty globules in the more peripheral portion.
Fine lipoid granules are also abundant in the central eytoplasm.
Ths great interstitial cell development forces apart the tubules
and doubles the diameter of the testis, which descends into
pouches essentially representing a scrotum remaining in com-
munication with the abdominal cavity proper. Spermatogenesis
suddenly shows renewed activity and free sperms are seen by the
506 ANDREW T. RASMUSSEN
last of March, or two to three weeks after waking up. The in-
terstitial cells do not, however, reach their maximal size till the
last of April. There is a distinct decrease in pigmentation.
4. Regressive spermatogenesis occurs during the last of
April and a new eyecle begins early in May, while the interstitial
cells remain greatly developed for at least two months longer.
5. By July the testes have returned to their abdominal position,
the interstitial cells begin to show signs of decrease and by
August most of them are reduced to almost nothing more than
naked nuclei. The eytoplasmic lipoids have been absorbed or
transformed into a new crop of pigment which remains as small
brown granules in the scanty cytoplasm in the form of a cap
covering about one-half of the nucleus. The nucleus is reduced
again in size. A number of the interstitial cells do not thus
decrease in size but remain large, the lipoids within them having
been transformed bodily, so to speak, into a pigmented substance
apparently of the same chemical nature as that of the smaller
pigment granules in the ordinary interstitial cells. The nucleus
of these special pigmented cells frequently is irregular or pyknotie
and may be forced to the periphery of the cell. The testis
as a whole is reduced to nearly one-eighth of its former size and
is darker in color than at any other stage. Spermatogenesis is
slowly progressing uninterruptedly.
6. A review of the literature on the correspondence between
interstitial cell activity, spermatogenesis, breeding period and
hibernation indicates great variability, with interstitial cell
growth more uniformly related to the later and regressive stages
of spermatogenesis than to the initial stages, though there seem
to be exceptions even to this generalization.
It affords me great pleasure to acknowledge the guidance received
from Dr. B. F. Kingsbury in this research, and the assistance of
Mr. R. S. Gutsell, in the retouching of the photographs.
SEASONAL CHANGES IN INTERSTITIAL CELLS 507
LITERATURE CITED
ALLEN, B. M. 1904 The embryonic development of the ovary and testis of the
mammals. Am. Jour. Anat., vol. 3, p. 89.
von BarDELEBEN, K. 1897 Beitrige zur Histologie des Hodens und zur
Spermatogenese beim Menschen. Arch. f. Anat. u. Physiol., Anat.
Abth., Suppl. Bd., p. 193.
Berssner, H. 1898 Die Zwischenzellen des Hodens und ihre Bedeutung.
Arch. f. mikr. Anat., Bd. 51, p. 794.
Betz, W. Blair 1916 The Sex Complex. New York.
Brensuey, R. R. 1911 Am. Jour. Anat., vol. 12, p. 309.
Bott, F. 1871 Untersuchungen itiber den Bau und die Entwickelung der
Gewebe. Arch f. mikr. Anat., Bd. 7, p. 275 (footnote p. 324).
Bourn ev ANcEL 1903 Recherches sur les cellules interstitielles du testicule
des mammiféres. Arch. d. zool. expér., Ser. 4, T. 1, p. 437.
1904 Recherches sur la signification physiologique de la glands inter-
stitielle du testicule des mammiféres. Jour. d. physiol. et de path.
gén., T. 4, p. 1012.
(And many other articles which may be obtained from the extensive
bibliography given by Biedl and by Tandler and Grosz.)
Cuampy, ©. 1908 Note sur les cellules interstitielles du testicule chez les
batraciens anoures. Compt. Rend. Soe. Biol., T. 64, p. 893.
CusuinG, H. and E. Gorrscn 1915 Hibernation and the pituitary body. Jour.
Exper. Med., vol. 22, p. 25.
DuesserG, J. 1917 Chondriosomes in the cells of fish-embryos. Am. Jour.
Anat., vol. 21, p. 465.
Finorti, E. 1897 Zur Pathologie und Therapie des Leistenhodens, nebst
einigen Bemerkungen iiber die grossen Zwischenzellen des Hodens.
Arch. f. klin. Chir., Bd. 35, p. 120.
FrRANKL, L. 1900 Beitrige zur Lehre vom Descensus testiculorum. Sitzungs-
ber. d. Kais. Akad. d. Wiss., Wien, Math.-Naturw. Kl., Abt. 3, Bd.
109, Heft 1.
FrrepMANN, F. 1898 Beitrige zur Kenntniss der Anatomie und Physiologie
der minnlichen Geschlechtsorgane. Arch. f. mikr. Anat., Bd. 52,
p. 856.
GANFINI, C. 1902 Struttura e sviluppo delle cellule, interstiziali del testiculo.
Arch. Ital. di Anat. e di Embri., T. 1, p. 233 and Compt. Rend. Soe.
BiOl 903 lero open lOUE
1903 Les cellules interstitielles du testicule chez les animaux hiber-
nants. Arch. Ital. d. Biol., T. 40, p. 323. (Apparently the complete
report was made in Bollettino della R. Accademia Medica di Genova,
1903.)
GOLDMANN, E. 8. 1909 Die diussere und innere Sekretion des gesunden und
kranken Organismus im Lichte der vitalen Farbung. Beitr. z. klin.
Chir, Bd: 64, p. 192.
Hanes, F. M. 1911 The relations of the interstitial cells of Leydig to the pro-
duction of an internal secretion by the mammalian testis. Jour.
Exper. Med., vol. 13, p. 338.
508 ANDREW T. RASMUSSEN
Hanes, F. M. and J. Rosensptoom 1911 A histological and chemical study of
the fatty matter of normal and eryptorchid testis. Jour. Exper.
Med., vol. 138, p. 355.
HANSEMANN, D. 1895 Uber die sogenannten Zwischenzellen des Hodens und
deren Bedeutung bei pathologischen Veriinderungen. Arch. f. path.
Anat. u. Physiol. u. f. klin. Med., Bd. 142, p. 538.
1896 Uber die grossen Zwischenzellen des Hodens. Arch. f. Anat.
u. Physiol., Physiol. Abt., p. 176.
1912. Kurze Bemerkungen iiber die Leydigschen Zwischenzellen des
Hodens. Arch. f. Entw. d. Organ., Bd. 34, p. 475.
Harmes, W. 1913 Die Brunstschwielen von Bufo vulgaris und die Frage ihrer
Abhingigkeit von den Hoden oder dem Bidderschen Organ; zugleich
ein Beitrag zur der Beteutung des Interstitiums. Zool. Anz., Bd. 42,
p. 462.
Hart, D. B. 1909 The nature and cause of the physiological descent of the
testis. Jour. Physiol., vol. 44, p. 4.
Hprxurimer, G. Uber Fett im Hoden bei Menschen (und Thieren). Sonder-
Abdruck aus der Orth-Festschrift.
Howe tt, A. H. 1915 North American Fauna, No. 37, Revision of the Ameri-
can Marmots, U. 8S. Dept. of Agri., Washington.
Iscovesco, H. 1913 Action physiologique d’un lipoide (II B b) extrait du
testicule. Compt. Rend. Soe. Biol., T. 75, p. 445.
Jackson, C. M. 1917 Effects of inanition and refeeding upon the growth and
structure of the hypophysis in the albino rat. Am. Jour. Anat., vol.
21, p: 321:
Krnassury, B. F. 1911 Histological demonstration of lipoids. Anat. Ree.,
vol. 5, sp. 313:
1914. The interstitial cells of the mammalian ovary: Felis domestica.
Am. Jour. Anat., vol. 16, p. 59.
Lécartton, A. 1909 Sur les cellules interstitielles du testicule de la taupe
(Talpa europaea) considéré en dehors de la période de reproduction.
Compt. Rend. Soc. Biol., T. 66, p. 599.
Kasat, K. 1908 Uber did Zwischenzellen des Hodens. Arch. f. path. Anat. u.
f. klin. Med., Bd. 194, p. 1.
Lennosstk, M. v. 1897 Beitrige zur Kenntniss der Zwischenzellen des Hodens.
Arch. f. Anat. u. Physiol., Anat. Abth., p. 665.
Lotset, G. 1902 Sur l’origine du testicule et sur sa nature glandulaire. Compt.
Rend. Soc. Biol., T. 54, p. 57.
Sur le lieu d’origine, la nature et le réle de la séerétion interne du tes-
ticule. Compt. Rend. Soe. Biol., T. 54, p. 1034.
Mann, F. C. 1916 The ductless glands and hibernation. Amer. Jour. Phys-
iol., vol. 41, p. 173.
Marsnauu, F. H. A. 1911 The male generative cycle in the hedgehog; with
experiments on the functional correlation between the essential and
accessory sexual organs. Jour. Physiol., vol. 43, p. 247.
Mazerti, L. 1911 I caratteri sessuali secondari e le cellule interstiziali del
testicolo. Anat. Anz., Bd. 38, p. 3561.
Merriam, C. H. 1884 The vertebrates of the Adirondack region, Northern
New York, (Mammalia). Trans. Linnaean Soc. N. Y., vol. 2, p. 142.
SEASONAL CHANGES IN INTERSTITIAL CELLS 509
Meves, F. 1908 Arch. f. mikr. Anat., Bd. 72, p. 832.
Meves, F. und J. Durspere 1908 Arch. f. mikr. Anat., Bd. 71, p. 573.
Morris, R. T. 1916 A ease of testicle grafting with unexpected results. Jour.
Amer. Med. Assoe., vol 67, p. 741.
Nusssaum, M. 1880 Von der Bedeutung der Hodenzwischensubstanz. Arch.
f. mikr. Anat., Bd. 18, p. 85.
Owen, R. 1868 Comparative Anatomy and Physiology of Vertebrates, Lon-
don, vol. 3, p. 649.
Pick, L. 1905 Uber Neubildungen am Genitale beim Zwitter, nebst Beitriigen
zur Lehre von den Adenomen des Hodens und EHierstocks. Arch. f.
Gyu., Bd. 76, p: 191.
Puarto, J. 1896 Die interstitiellen Zellen des Hodens und ihre physiologische
Bedeutung. Arch. f. mikr. Anat., Bd. 48, p. 280.
1897 Zur Kenntniss der Anatomie und Physiologie der Geschlechts-
organe. Arch. f. mikr. Anat., Bd. 50, p. 640.
Reeavup, C. 1901 Etudes sur les structure des tubules seminiféres et sur les
spermatogenése chez les mammiféres. Arch. d’Anat. Mikr., T. 4,
jo LONE
1904 Etat des cellules interstitielles du testicule chez la taupe pen-
dant la période de spermatogenése et pendant l’état de repos des
canalicules séminaux. Compt. Rend. d. l’Assoe. d. Anat., p. 54.
Reinke, F. 1896 Beitriige zur Histologie des Menschen. I. Uber Krystal-
loidbildungen in den interstitiellen Zellen des menschlichen Hodens.
Arch. f. mikr. Anat., Bd. 47, p. 34.
Seurt, E. 1904 Zur Kenntniss der Fetthaltigen Pigmente. Arch. f. path.
Anat. u. Physiol. u. f. klin. Med., Bd. 177, p. 248.
Spanearo, 8S. 1901 Uber die histologischen Veranderungen des Hodens, Neben-
hodens und Samenleiters von Geburt an bis zum Greisenalter. Anat.
Hefte, Bd. 18, p. 592.
TANDLER, J. UND S. Grosz 1911-1912 Uber den Saisondimorphismus des
Maulwurfhodens. Arch. f. Entw. der Organ., Bd. 33, p. 297 and
Bd. 35, p.. 132:
WuitrrHEaD, R. H. 1904 The embryonic development of the interstitial cells
of Leydig. Am. Jour. Anat., vol. 3, p. 167.
1905 Studies of the interstitial cells of Leydig. Am. Jour. Anat.,
vol. 4, p. 198.
1906 The presence of granules in the interstitial cells of the testis.
Anat. Rec., vol. 1, p..60.
1908 a A peculiar case of cryptorchism, and its bearing upon the
problem of the function of the interstitial cells of the testis. Anat.
Ree., vol. 2, p. 177.
1908 b Studies of the interstitial cells of Leydig. No.3. Histology.
Anat. Rec., vol. 1, p. 218.
1912 a On the chemical nature of certain granules in the interstitial
cells of the testis. Am. Jour. Anat., vol. 14, p. 63.
1912 b A microchemical study of the fatty bodies in the interstitial
cells of the testis. Anat. Rec., vol. 6, p. 65.
WitpMan, E. E. 1913 Jour. Morph., vol. 24, p. 426 (footnote).
PLATE 1
EXPLANATION OF FIGURES
1 Photograph of section of testis of adult woodchuck in early stage of
hibernation; Dec. 1; rectal temperature 19°C.; reduced body weight 2525 grams,
of which one testis constituted 0.034 per cent. Carnoy’s fluid; 4 u thick; iron
hematoxylin. X 129. Testes abdominal. Shows the relative amount of in-
terstitial tissue. Tubules filled with spermatocytes.
2 Retouched photograph of characteristic interstitial space of above section
under higher magnification. X 527. Many small ordinary interstitial cells
with pigment granules stained black. Three large interstitial cells so filled with
large pigment granules that nucleus is obscured.
3 Retouched photograph of section of testis of above animal showing a
characteristic group of large and especially pigmented interstitial cells. Car-
noy’s fixer; 44 thick; hematoxylin and eosin. X 527. Nucleus is irregular and
frequently displaced. A few ordinary interstitial cells, containing a few pigment
granules, are present.
4,5 Retouched photographs of newly formed ‘pigment cells’ from same ani-
mal as in figure 23, under higher magnification. X 1053. In figure 5 the pig-
ment granules appear to have a peripheral distribution, occupying the position
of the fat globules from which they were evidently formed.
6 Photograph of a section of the testis of adult woodchuck in last stage of
hibernation; March 6; rectal temperature 12°C.; reduced body weight 1849 grams,
about two-thirds of the weight before hibernation. Same technique and mag-
nification as in figure 1. Testes abdominal. Animal beginning to wake up.
7 Retouched photograph of section of testis of same animal as in figure 6.
Modified Zenker’s fluid; 4u thick; copper hematoxylin (Weigert). X 527. Many
granules (lipoid?) in addition to pigment. One large heavily pigmented cell
present.
8 Camera lucida drawing of cell pictures not infrequently met with during
the enlarging period in the interstitial cell cycle. Carnoy’s fluid; 4 » thick;
iron hematoxylin. X 527. <A suggestion that there has been nuclear division.
9 Retouched photograph of interstitial cell at maximal stages of develop-
ment containing two nuclei. Carnoy’s fluid; 4 » thick; iron hematoxylin.
x 1053.
10 Photograph of section of testis of adult woodchuck with interstitial cells
maximal; May 8. Carnoy’s fixer; 6 w thick; iron hematoxylin. X 200. Illus-
trates how the interstitial cells tend to be arranged in ‘nests’ in about half of
the animals in which the interstitial cells were greatly developed.
510
SEASONAL CHANGES IN INTERSTITIAL CELLS PLATE 1
ANDREW T. RASMUSSEN
PLATE 2
EXPLANATION OF FIGURES
11 Photograph of section of testis of adult woodchuck practically at full
activity and been so for a week or more; March 21; rectal temperature 32°C.;
reduced body weight 1650 (about two-thirds of original weight before hiberna-
tion). Testes abdominal. Carnoy’s fluid; 4 » thick; iron hematoxylin. X 129.
Interstitial cells have greatly increased.
12 Retouched photograph of a mass of interstial cells from preceding section
under higher magnification. X 527. Pigment scattered out in the abundant
cytoplasm which is vacuolated from having fat dissolved out.
13 Retouched photograph of a group of interstitial cells from testis of same
animal as in figures 11 and 12. Modified Zenker’s; 44 thick; copper hematoxylin.
x 527. Various stages in the expansion of the cells.
14. Photograph of section of testis of same animal as in preceding figures in
this plate. Meves’ fixer; 4 u thick; unstained and uncovered. X 129. Fatty
globules blackened with the osmic acid. Tubules contain much fat. Five
adipose cells are present (four in one group). Large blood vessels. Section too
near the surface of block to be perfect.
15 Photograph of section of testis of adult woodchuck when interstitial cells
are maximal; during full activity and after feeding at least six weeks; May 10;
rectal temperature 37°C.; reduced body weight 2420, of which one testis consti-
tuted 0.111 per cent. Testes scrotal. Same technique and magnification as in
figures 1, 6 and 11.
16 Retouched photograph of interstitial cells of preceding section under
higher magnification. X 527. Pigment nearly absent. Central cytoplasm
finely vacuolated (seen best in the cell marked with a +); peripheral cytoplasm
coarsely vacuolated. Vacuoles due to dissolving out the lipoids. To be com-
pared with figures 2 and 24.
17 Retouched photograph of interstitial cells of same.animal as in figures
15 and 16. Modified Zenker’s, ete., as in figures 7 and 13. X 527. The fine
vacuoles of figure 16 are here filled with granules (lipoid) stained black. Periph-
eral fat not stained.
18 Photograph of section of testis with interstitial cells maximal. Meves’
fixer, etc., as in figure 14. X 129. Peripheral fat of interstitial cells and adi-
pose cells black. Two blood vessels. Insert shows three cells more highly
magnified. X 527. Nucleus of one cell shown as white spot. Section too near
the periphery of block to be perfect. The poor penetrating power of osmic
acid and the distortion of the testicular contents at the cut surface made perfect
sections illustrating relative amount of fat unavailable.
512
SEASONAL CHANGES IN INTERSTITIAL CELLS PLATE 2
ANDREW T. RASMUSSEN
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PLATE 3
EXPLANATION OF FIGURES
19 Photograph of a section of testis of adult woodchuck with interstitial
cells at a maximum; April 29; reduced body weight 2850 grams, of which one
testis constituted 0.106 per cent. Carnoy’s fixer; 4 » thick; iron hematoxylin.
<x 20. The + is placed on a large nodule of interstitial cells which are especially
rich in fat. Lumen of tubules open.
20 Photograph of section of testis of adult woodchuck with interstitial cells
beginning to atrophy; July 10; reduced body weight 2825 grams, of which one
testis represents 0.038 per cent. Testes still scrotal. Carnoy’s fixer; 4 thick;
iron hematoxylin. Tubules no longer open. To be compared directly with
figure 15.
21 Retouched photograph of section of testis of same animal as in figure 20.
Modified Zenker’s fluid; 4 u thick; copper hematoxylin. X 527. Central cyto-
plasm still contains numerous fine granules (lipoid) in addition to pigment.
To be eomnared directly with figure 17.
22 Photograph of section of testis of same animal as in two preceding figures.
Meves’ fixer; 4 4 thick; unstained and uncovered. X 129. A number of large
globules of fat are still left in the interstitial cells. To be compared directly
with figures 18 and 14.
23. Photograph of section of testis of adult woodchuck just after atrophy of
interstitial cells; August 5; reduced body weight 3190 grams, of which one testis
represents 0.016 per cent. Testes abdominal. Carnoy’s fixer; 4 » thick; iron
hematoxylin. X 129. Interstitial cells numerous but greatly reduced in size.
Tubules contain many spermatocytes.
24. Retouched photograph of above section under higher magnification.
527. In addition to numerous ordinary interstitial cells, now rich in pigment
but greatly reduced in size, there are four newly formed ‘pigment cells’ easily
distinguishable by their large size, darker color and numerous large pigment
granules. :
25 Photograph of a portion of the section immediately following under
higher magnification. 527. A group of newly formed ‘pigment cells’ as they
appear after being acted upon by osmie acid. Only colored plates could do
justice to their appearance as seen when the pigment is unstained such as occurs
after Carnoy’s fixer and hematoxylin and eosin. Carnoy’s fixer tends to make
them more irregular in outline as may be seen by comparing this figure with
figures 4 and 5, all of which are from sections of the same animal.
26 Photograph of section of testis of this last animal; Meves’ fixer; 4 » thick;
unstained and uncovered. > 129. The osmie acid darkens the pigment gran-
ules of the interstitial cells and blackens the fatty globules in the tubules as
well as ordinary adipose cells, which now are very numerous. The large newly
formed ‘pigment cells’ stand out prominently. There is a striking absence of
fat globules in the interstitial cells. Compare with figure 18.
514
SEASONAL CHANGES IN INTERSTITIAL CELLS PLATE 3
ANDREW T. RASMUSSEN
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SUBJECT AND AUTHOR INDEX
LBINO rat. Studies on the mammary
gland. II. The fetal development of
the mammary gland in the female.... 195
Ammocoetes. The relationships and histo-
genesis of thymus-like structures in...... 127
Anomalies in the human embryos and infants
at birth. On the frequency of localized.. 49
ArREy, LesytieE B. The normal shape of the
mammalian red blood corpuscle........... 439
Armadillo, Tatusia novemeincta. The early
history of the germ cells in the........... 341
ANKS, J. B., Jorpan, H. E. anp. A
study of the intercalated dises of the
Nearh, OfmuesIOe lier Pee srathes «<4 agers» 285
BAUMGARTNER, E. A. The development of
the serous glands (von Ebner’s) of the
vallate papillae in man................... 365
Beef. A study of the intercalated dises of the
Heart Opbhern.enstat hos oan. cane 285
Behavior of chicken bone marrow in plasma
medium. Cytological observations on the. 73
Birth. On the frequency of localized anoma-
lies in the human embryos and infants
SRL eee. TE Tope ee aps 2 ass a = rc fer 49
Blood corpuscle. The normal shape ,of the
PREC LETH ACL] VEN cp Ce10 Lene as “Uma 8 ks Oe 439
BOLE wines Onimetopism..2: sjacebete sce eae < 6 27
Bone marrow in plasma medium. Cyto-
logical observations on the behavior of
UI CKOD: pete See oes. c. ee ET te ce ave 73
Oak vey? of the ear in the human embryo.
The factors involved in the excavation
__ of the cavities in the cartilaginous..... 1
Cartilaginous capsule of the ear in the human
embryo. The factors involved in the ex-
cavation of the cavitiesin the............ 1
The early history of the germ............ 341
Cells in the armadillo, Tatusia novemcincta.
The early history of the germ............ 341
Cells of the testis in the woodchuck (Marmota
monax). Seasonal changes in the inter-
iin CU eee oe DIR Outen, 475
Changes in the interstitial cells of the testis
in the woodchuck (Marmota monax).
USES DI Ae co, ue Deeds Bog ado00 b> TOBe aoa 475
Chicken bone marrow in plasma medium.
Cricloeieal observations on the behavior
o
Corpusele. The normal shape of the mam-
MAMA TECIDIOOM sere series ces ss + sess 439
Cross striated muscle in tissue cultures. Be-
A VIOT OLN. ee eM niclejale Dis aceie:s ov 169
Cultures. Behavior of cross striated muscle
INGIBSUG. «... eee ate cece des ce aes 169
Cycle in the guinea-pig—with a study of its
histological and physiological changes.
he existence of a typical oestrous........ 225
Cytological observations on the behavior of
chicken bone marrow in plasma medium. 73
ISCS of the heart of the beef. A study
of fhe intercalated & weit) sass. 285
AR in the human embryo. The factors
involved in the excavation of the cavi-
ties in the cartilaginous capsule of
ibnt hi RN arior GoaGHOS oeOreOOOr: {Cb DrtoODe 49
ERDMANN, Ruopa. Cytological observations
on the behavior of chicken bone marrow
in plasma Medium.....5-.- ee0-<c- eee oes 73
ACTORS involved in the excavation of
KF the cavities in the cartilaginous capsule
of the ear inthe human embryo. The. 1
Fetal development of the mammary gland
in the female albino rat. Studies on the
mammary gland. IJ. The.............. os» 195
Foetus exhibiting bilateral absence of th
ulna accompanied by monodactyly (and
also diaphragmatic hernia). Anatomy
Of a SevenimMOnuhs) a: dae cent cele 385
Studies on the mammary............. eee 195
Glands (von Ebner’s) of the vallate papillae
inman. The development of the serous. 365
Guinea-pig—with a study of its histological
and physiological changes. The existenee
of a typical oestrous cycle in the......... 225
EART of the beef. A study of the inter-
calated Gises Of th@sos..-n-2- 2+ esr 285
Hernia. Anatomy of a seven months’ foetus
exhibiting bilateral absence of the ulna
accompanied by monodactyly (and also
diaphragmatic) ..........--.+++++.-+-++: -- 385
Histogenesis of thymus-like structures in
Ammocoetes. The relationships and..... 127
Human embryos and infants at birth. On
the frequency of localized anomalies in
HOMME voxacielcacters conve ce RR 3 ater oreieeere caret» 49
Human embryo. The factors involved in the
excavation of the cavities in the carti-
laginous capsule of the ear in the......... 1
| izes at birth. On the frequency of
localized anomalies in the human em-
DEY OS\AN Gen. sc-ea ere hay ORE NEY. oe 49
Interealated dises of the heart of the beef.
Atatidy Of thes. numer reer iaiale 6 2/5: oais:-
Interstitial cells of the testisin the woodchuck
(Marmota monax). Seasonal changes in
nt Ret he agg — dono Ab caaeibE DonOos 475
ORDAN, H.E. anv Banks, J.B. A study
of the intercalated discs of the heart of
bhie: beet sees «tere + caenele ake oft --oIbubs sineyatainvact 285
EWIS, Warren H. anp Marcaret R.
Behavior of cross striated muscle in tis-
BUC CUlGUTES: Meat ee oe = oats clad ein stele 169
517
518
Lewis, MarGAretT R., WARREN H. AND. | Be-
havior of cross striated muscle in tissue
Oulturos eee titctetom eka we clerersieeicers ale
ALL, Franxuin P. On the frequency of
localized anomalies in the human em-
bryos and infants at birth.............
Mammalian red blood ea The nor-
mal shape of the....... . ‘
Mammary gland. II. The fetal develop-
ment of the mammary gland in the female
albino rat. Studies on the...............
Man. The development of the serous glands
INDEX
169
49
439
(von Ebner’s) of the vallate papillae ane
(Marmbtn Monax). Seasonal changes in the
interstitial cells of the testis in the wood-
Chucks 25 cscs aera DOC ahs Per eitie ate ie ieep
Marrow in plasma medium. Cytological
observations on the behavior of chicken
BODO Se forctee cic rorccetere te tiae eos eee loiele nie wet antics akete
Motopismis Ont ie oos iaosin ban enemas
Monax). Seasonal changes in the interstitial
cells of the testis in the woodchuck........ 475
Monodactyly (and also diaphragmatic hernia).
Anatomy of a seven months’ foetus ex-
hibiting bilateral absence of the ulna
ACCOMP ANIed Ny meena ceciacis ss ncelo stereos.
Muscle in tissue cultures. Behavior of cross
P|: iCclo Danae en ete Cian PRN Gis eased
Myers, J. A. Studies on the mammary
gland. II. The fetal development of the
mammary gland in the female albino
DU sercictctercielajn)a teierevarcie revere) sieievaletetle oye telers s (efeteke
OVEMCINCTA. The early history of
It the germ cells in the armadillo, Tatusia.
ESTROUS cyele in the guinea-pig—with
a study of its histological and physio-
logical changes. The existence of a
GY PICA PE Fo acc eMeicira ie ilalete eistaretajere oe
APILLAE in man. The development of
the serous glands (von Ebner’s) of the
Wallate re She cst ce oe poe enon a taeeies
Plasma medium. Cytological observations
on the behavior of chicken bone marrow
ASMUSSEN, Anprew_ T. _ Seasonal
changes in the interstitial cells of the
testis in the woodchuck (Marmota
INONRE) Aer cta saree een arise eeete eee eee
Rat. Studies on the mammary gland. II.
The fetal development of the mammary
gland in the female albino................
195
341
225
365
73
475
Red blood corpuscle. The normal shape of
the vam aa arnt ioys) sees oveve ls rcvexepl acevetenmenerer ete
EASONAL changes in the interstitial cells
of the testis in the woodchuck (Marmota
monax)
Serous glands (von Ebner’s) of the vallate
, papillae in man. The development of
The normal
SrocKarRD, CHARLES R. AND PAPANICOLAOU,
Grorce N. The existence of a typical
oestrous cycle in the guinea-pig—with a
study of its histological and physiological
ChAN BES Si tivecatie c otiave. ane act een eee
StrREETER, GEORGE L. The factors involved
in the excavation of the cavities in the
cartilaginous capsule of the ear in the
human (embryos. aewtnoss see eee
Striated muscle in tissue cultures. Behavior
OMCTOSS! iene tyne Oe Sehicle cae eee 1
Tee novemcincta. The early his-
tory of the germ cells in the arma-
Testis in the woodchuck (Marmota monax).
Seasonal changes in the interstitial cells
OF the sc een eee as basis memes
Thymus-like structures in Ammocoetes.
relationships and histogenesis of..........
Tissue cultures. Behavior of cross striated
TMUSCLS HTT 3.515 laaictetelere 1 siese's ote tecore eueters ieretenets 1
| Weer accompanied by monodactyly (and
also diaphragmatic hernia). Anatomy
of a seven months’ foetus exhibiting bi-
lateral/absence!of the: -co..sece-emeceens
ALLATE papillae inman. The develop-
mentfof the serous glands (von Ebner’s)
225
385
Qin panameses AAAOnAacoaccng soo OCOo NC 365
VANNEMAN, Armes S. The early history of
the germ cells in the armadillo, Tatusia
MOVSIM CINCEA.,.. oh anne crecisiee sealer araieerers
ALLIN, Ivan E. The relationships
and histogenesis of thymus-like
structures in Ammocoetes............
Watt, JAMES CrRAwrorD. Anatomy of a
seven months’ foetus exhibiting bilateral
absence of the ulna accompanied by mono-
dactyly (and also diaphragmatic hernia).
Woodchuck (Marmota monax). Seasonal
changes in the interstitial cells of the
testisiin the. as carcestecases seine beatae 47
341
127
385
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