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UNIVERSITY OF KANSAS PUBLICATIONS
MUSEUM OF NATURAL HISTORY
Volume 8, No. 2, pp. 157-211, figures 1-23, 4 tables
---------------------- November 15, 1954 ----------------------
Myology and Serology
of the Avian Family Fringillidae,
A Taxonomic Study
BY
WILLIAM B. STALLCUP
UNIVERSITY OF KANSAS
LAWRENCE
1954
UNIVERSITY OF KANSAS PUBLICATIONS, MUSEUM OF NATURAL HISTORY
Editors: E. Raymond Hall, Chairman, A. Byron Leonard,
Robert W. Wilson
Volume 8, No. 2, pp. 157-211, figures 1-23, 4 tables
Published November 15, 1954
UNIVERSITY OF KANSAS
Lawrence, Kansas
PRINTED BY
FERD VOILAND, JR., STATE PRINTER
TOPEKA, KANSAS
1954
[Union Label]
25-4632
Myology and Serology
of the Avian Family Fringillidae,
A Taxonomic Study
BY
WILLIAM B. STALLCUP
CONTENTS
PAGE
INTRODUCTION 160
MYOLOGY OF THE PELVIC APPENDAGE 162
General Statement 162
Materials and Methods 163
Description of Muscles 164
Discussion of Myological Investigations 175
COMPARATIVE SEROLOGY 185
General Statement 185
Preparation of Antigens 186
Preparation of Antisera 188
Methods of Serological Testing 188
Experimental Data 190
Discussion of Serological Investigations 190
CONCLUSIONS 201
SUMMARY 208
LITERATURE CITED 210
INTRODUCTION
The relationships of many groups of birds within the Order
Passeriformes are poorly understood. Most ornithologists agree that
some of the passerine families of current classifications are
artificial groups. These artificial groupings are the result of early
work which gave chief attention to readily adaptive external
structures. The size and shape of the bill, for example, have been
over-emphasized in the past as taxonomic characters. It is now
recognized that the bill is a highly adaptive structure and that it
frequently shows convergence and parallelism.
Since studies of external morphology have failed in some cases to
provide a clear understanding of the relationships of passerine birds,
it seems appropriate that attention be given to other morphological
features, to physiological features, and to life history studies in an
attempt to find other clues to relationships at the family and
subfamily levels.
This paper reports the results of a study of the relationships of some
birds of the Family Fringillidae and is based on the comparative
myology of the pelvic appendage and on the comparative serology of
saline-soluble proteins. Where necessary for comparative purposes,
birds from other families have been included in these investigations.
It has long been recognized that the Fringillidae include dissimilar
groups. Recent work by Beecher (1951b, 1953) on the musculature of the
jaw and by Tordoff (1954) primarily on the structure of the bony
palate has emphasized the artificial nature of the assemblage although
these authors disagree regarding major divisions within it (see
below).
The Fringillidae have been distinguished from other families of
nine-primaried oscines by only one character--a heavy and conical bill
(for crushing seeds). Bills of this form have been developed
independently in several other, unrelated, groups; as Tordoff (1954:7)
has pointed out, _Molothrus_ of the Family Icteridae, _Psittorostra_
of the Family Drepaniidae, and most members of the Family Ploceidae
have bills as heavy and conical as those of the fringillids. The
ploceids are distinguished from the fringillids by a single external
character: a fairly well-developed tenth primary whereas in
fringillids the tenth primary is absent or vestigial. Tordoff
(1954:20) points out, however, that this distinction is of limited
value since in other passerine families the tenth primary may be
present in some species of a genus and absent in others. The Genus
_Vireo_ is an example. Furthermore, at least one ploceid
(_Philetairus_) has a small, vestigial tenth primary, whereas some
fringillids (_Emberizoides_, for example) possess a tenth primary
which is rather large and ventrally placed (Chapin, 1917:253-254).
Thus, it is obvious that studies based on other features are necessary
in order to attain a better understanding of the relationships of the
birds involved.
Sushkin's studies (1924, 1925) of the structure of the bony and horny
palates have served as a basis for the division of the Fringillidae
into as many as five subfamilies (Hellmayr, 1938:v): Richmondeninae,
Geospizinae, Fringillinae, Carduelinae, and Emberizinae.
Beecher (1951b:280) points out that "the richmondenine finches arise
so uninterruptedly out of the tanagers that ornithologists have had
to draw the dividing line between the two groups arbitrarily." His
study of pattern of jaw-musculature substantiates this. He states
further that the cardueline finches arise without disjunction
from the tanagers. He suggests, therefore, that the two groups of
"tanager-finches" be made subfamilies of the Thraupidae and that a
third subfamily be maintained for the more typical tanagers. He states
that the emberizine finches are of different origin, arising from the
wood warblers (1953:307). Beecher (1951a:431; 1953:309) includes the
Dickcissel, _Spiza americana_, in the Family Icteridae, chiefly on the
basis of jaw muscle-pattern and the horny palate.
Tordoff (1954:10-11) presents evidence that the occurrence of
palato-maxillary bones in nine-primaried birds indicates relationship
among the forms possessing them. He points out that all fringillids
except the Carduelinae possess palato-maxillaries that are either free
or more or less fused to the prepalatine bar. He points out also that
in all carduelines, the prepalatine bar is flared at its juncture with
the premaxilla, and that the mediopalatine processes are fused across
the midline; noncardueline fringillids lack these characteristics. In
addition to the above he cites differences between the carduelines and
the "other" fringillids in the appendicular skeletons, in geographic
distribution, in patterns of migration, and in habits. Tordoff
concludes, therefore, that the carduelines are not fringillids but
ploceids, their closest affinities being with the ploceid Subfamily
Estrildinae. On the basis of palatal structure, the Fringillinae and
Geospizinae are combined with the Emberizinae, the name Fringillinae
being maintained for the subfamily. The tanagers merge with the
Richmondeninae on the one hand and with the Fringillinae on the other.
On this basis, Tordoff (1954:32) suggests that the Family Fringillidae
be divided into subfamilies as follows: Richmondeninae, Thraupinae,
and Fringillinae. The carduelines are placed as the Subfamily
Carduelinae in the Family Ploceidae.
From the foregoing, it is apparent that the two most recent lines of
research have given rise to conflicting theories regarding
relationships within the Family Fringillidae. The purpose of my
investigation, therefore, has been to gather information, from other
fields, which might clarify the relationships of these birds.
Since the muscle pattern of the leg in the Order Passeriformes is
thought to be one of long standing and slow change, any variation
which consistently distinguishes one group of species from another
could be significant. With the hope that such variation might be
found, a study of the comparative myology of the legs was undertaken.
The usefulness of comparative serology as a means of determining
relationship has been demonstrated in many investigations. Its use in
this instance was undertaken for several reasons: comparative serology
has its basis in biochemical systems which seem to evolve slowly; its
methods are objective; and its use has, heretofore, resulted in the
accumulation of data which seem compatible, in most instances, with
data obtained from other sources.
I acknowledge with pleasure the guidance received in this study from
Prof. Harrison B. Tordoff of the University of Kansas. I am indebted
also to Prof. Charles A. Leone without whose direction and assistance
the serological investigations would not have been possible; to
Professors E. Raymond Hall and A. Byron Leonard whose suggestions and
criticisms have been most helpful in the preparation of this paper;
and to T. D. Burleigh of the U. S. Fish and Wildlife Service for gifts
of several specimens used in this work. Assistance with certain parts
of the study were received from a contract (NR163014) between the
Office of Naval Research of the United States Navy and the University
of Kansas.
MYOLOGY OF THE PELVIC APPENDAGE
General Statement
In an excellent paper in which the muscles of the pelvic appendage of
birds are carefully and accurately described, Hudson (1937) reviewed
briefly the more important literature pertaining to the musculature of
the leg which had been published to that date. A review of such
information here, therefore, seems unnecessary.
Myological formulae suggested by Garrod (1873, 1874) have been
extensively used by taxonomists as aids in characterizing the orders
of birds. Relatively few investigations, however, involving the
comparative myology of the leg have been undertaken at family and
subfamily levels. The works of Fisher (1946), Hudson (1948), and
Berger (1952) are notable exceptions.
The terminology for the muscles used in this paper follows that of
Hudson (1937), except that I have followed Berger (1952) in Latinizing
all names. Homologies are not given since these are reviewed by
Hudson. Osteological terms are from Howard (1929).
Materials and Methods
Specimens were preserved in a solution of one part formalin to eight
parts of water. Thorough injection of all tissues was necessary for
satisfactory preservation. Most of the down and contour feathers were
removed to allow the preservative to reach the skin.
In preparing specimens for study, the legs and pelvic girdle were
removed and washed in running water for several hours to remove much
of the formalin. They were then transferred to a mixture of 50 per
cent alcohol and a small amount of glycerine.
All specimens were dissected with the aid of a low power binocular
microscope. Where possible, several specimens of each species were
examined for individual differences. Such differences were found to be
slight, involving mainly size and shape of the muscles. The size is
dependent partly on the age of the bird, muscles from older birds
being larger and better developed. The shape of a muscle (whether long
and slender or short and thick) is due in part to the position in
which the leg was preserved; that is to say, a muscle may be extended
in one bird and contracted in another. For these reasons, descriptions
and comparisons are based mainly on the origin and insertion of a
muscle and on its position in relation to adjoining muscles.
Birds dissected in this study are listed below (in the order of the A.
O. U. Check-List):
SPECIES
_Vireo olivaceus_ (Linnaeus) _Leucosticte tephrocotis_
_Seiurus motacilla_ (Vieillot) (Swainson)
_Passer domesticus_ (Linnaeus) _Spinus tristis_ (Linnaeus)
_Estrilda amandava_ (Linnaeus) _Loxia curvirostra_ Linnaeus
_Poephila guttata_ (Reichenbach) _Chlorura chlorura_ (Audubon)
_Icterus galbula_ (Linnaeus) _Pipilo erythrophthalmus_
_Molothrus ater_ (Boddaert) (Linnaeus)
_Piranga rubra_ (Linnaeus) _Calamospiza melanocorys_
_Richmondena cardinalis_ (Linnaeus) Stejneger
_Guiraca caerulea_ (Linnaeus) _Chondestes grammacus_ (Say)
_Passerina cyanea_ (Linnaeus) _Junco hyemalis_ (Linnaeus)
_Spiza americana_ (Gmelin) _Spizella arborea_ (Wilson)
_Hesperiphona vespertina_ (Cooper) _Zonotrichia querula_ (Nuttall)
_Carpodacus purpureus_ (Gmelin) _Passerella iliaca_ (Merrem)
_Pinicola enucleator_ (Linnaeus) _Calcarius lapponicus_ (Linnaeus)
Description of Muscles
The descriptions which follow are those of the muscles in the leg of
the Red-eyed Towhee, _Pipilo erythrophthalmus_. Differences between
species, where present, are noted for each muscle. The term thigh is
used to refer to the proximal segment of the leg; the term crus is
used for that segment of the leg immediately distal to the thigh.
_+Musculus iliotrochantericus posticus+_ (Fig. 2).--The origin of this
muscle is fleshy from the entire concave lateral surface of the ilium
anterior to the acetabulum. The fibers converge posteriorly, and the
muscle inserts by a short, broad tendon on the lateral surface of the
femur immediately distal to the trochanter. It is the largest muscle
which passes from the ilium to the femur.
Action.--Moves femur forward and rotates it anteriorly.
Comparison.--No significant differences noted among the species
studied.
_+Musculus iliotrochantericus anticus+_ (Fig. 3).--Covered laterally
by the _m. iliotrochantericus posticus_, this slender muscle
has a fleshy origin from the anteroventral edge of the ilium
between the origins of the _m. sartorius_ anteriorly and the _m.
iliotrochantericus medius_ posteriorly. The _m. iliotrochantericus
anticus_ is directed caudoventrally and inserts by a broad, flat
tendon on the anterolateral surface of the femur between the heads of
the _m. femorotibialis externus_ and _m. femorotibialis medius_ and
just distal to the insertion of the _m. iliotrochantericus medius_.
Action.--Moves femur forward and rotates it anteriorly.
Comparison.--No significant differences noted among the species studied.
_+Musculus iliotrochantericus medius+_ (Fig. 3).--Smallest of the
three _iliotrochantericus_ muscles, this bandlike muscle has a fleshy
origin from the ventral edge of the ilium just posterior to the origin
of the _m. iliotrochantericus anticus_. The fibers are directed
caudoventrally, and the insertion is tendinous on the anterolateral
surface of the femur between the insertion of the other two
_iliotrochantericus_ muscles.
Action.--Moves femur forward and rotates it anteriorly.
Comparison.--No significant differences noted among the species
studied.
_+Musculus iliacus+_ (Figs. 4, 5).--Arising from a fleshy origin on
the ventral edge of the ilium just posterior to the origin of the _m.
iliotrochantericus medius_, this small slender muscle passes
posteroventrally to its fleshy insertion on the posteromedial surface
of the femur just proximal to the origin of the _m. femorotibialis
internus_.
Action.--Moves femur forward and rotates it posteriorly.
Comparison.--No significant differences among the species studied.
_+Musculus sartorius+_ (Figs. 1, 4).--A long, straplike muscle, the
_sartorius_ forms the anterior edge of the thigh. The origin is
fleshy, half from the anterior edge of the ilium and from the median
dorsal ridge of this bone and half from the posterior one or two free
dorsal vertebrae. The insertion is fleshy along a narrow line on the
anteromedial edge of the head of the tibia and on the medial region of
the patellar tendon.
Action.--Moves thigh forward and upward and extends shank.
Comparison.--In _Loxia_ and _Spinus_, only one-third of the origin is
from the last free dorsal vertebra. In _Hesperiphona_, _Carpodacus_,
_Pinicola_, and _Leucosticte_, only one-fifth of the origin is from
this vertebra.
_+Musculus iliotibialis+_ (Fig. 1).--Broad and triangular, this muscle
covers most of the deeper muscles of the lateral aspect of the thigh.
The middle region is fused with the underlying _femorotibialis_
muscles. In the distal half of this muscle there are three distinct
parts; the anterior and posterior edges are fleshy and the central
part is aponeurotic. The origin is from a narrow line along the iliac
crests--from the origin of the _m. sartorius_, anteriorly, to the
origin of the _m. semitendinosus_ posteriorly. The origin is
aponeurotic in the preacetabular region but fleshy in the
postacetabular region. The distal part of the muscle is aponeurotic
and joins with the _femorotibialis_ muscles in the formation of the
patellar tendon. This tendon incloses the patella and inserts on a
line along the proximal edges of the cnemial crests of the
tibiotarsus.
Action.--Extends crus.
Comparison.--In _Vireo_ the central aponeurotic portion of this muscle
is absent.
_+Musculus femorotibialis externus+_ (Fig. 2).--Covering the lateral
and anterolateral surfaces of the femur, this large muscle has a
fleshy origin from the lateral edge of the proximal three-fourths of
the femur. The origin separates the insertion of the _m.
iliotrochantericus anticus_ from that of the _m. ischiofemoralis_ and,
in turn, is separated from the origin of the _m. femorotibialis
medius_ by the insertions of the _m. iliotrochantericus anticus_ and
_m. iliotrochantericus medius_. Approximately midway of the length of
the femur this muscle fuses anteromesially with the _m. femorotibialis
medius_. Distally, the _m. femorotibialis externus_ contributes to the
formation of the patellar tendon which inserts on a line along the
proximal edges of the cnemial crests of the tibiotarsus.
Action.--Extends crus.
Comparison.--No significant differences noted among the species studied.
_+Musculus femorotibialis medius+_ (Figs. 2, 4).--The origin of this
muscle, which lies along the anterior edge of the femur, is fleshy
from the entire length of the femur proximal to the level of
attachment of the proximal arm of the biceps loop. Laterally this
muscle is completely fused for most of its length with the _m.
femorotibialis externus_ and contributes to the formation of the
patellar tendon, which inserts on a line along the proximal edges of
the cnemial crests of the tibiotarsus. Many of the fibers,
nevertheless, insert on the proximal edge of the patella.
Action.--Extends crus.
Comparison.--No significant differences noted among the species
studied.
_+Musculus femorotibialis internus+_ (Fig. 4).--One of the most
superficial muscles lying on the medial surface of the thigh, this
muscle is divided, especially near the distal end, into two parts,
lateral and medial. The origin of the lateral part is fleshy from a
line on the medial surface of the femur; the origin begins proximally
at a point near the insertion of the _m. iliacus_. The medial, bulkier
part of the muscle has a fleshy origin on the medial surface of the
lower one-third of the femur. The two parts fuse to some extent above
the points of insertion and insert on the medial edge of the head of
the tibia.
Action.--Rotates tibia anteriorly.
Comparison.--Two parts of this muscle variously fused; otherwise, no
significant differences in the species studied.
_+Musculus piriformis+_ (Fig. 3).--This muscle is represented by the
_pars caudifemoralis_ only, the _pars iliofemoralis_ being absent in
passerine birds as far as is known. The _pars caudifemoralis_ is flat,
somewhat spindle-shaped, and passes anteroventrally from the pygostyle
to the femur. The origin is tendinous from the anteroventral edge of
the pygostyle, and the insertion is semitendinous on the
posterolateral surface of the shaft of the femur about one-fourth its
length from the proximal end.
Action.--Moves femur posteriorly and rotates it in this direction;
moves tail laterally and depresses it.
Comparison.--No significant differences noted among the species
studied.
_+Musculus semitendinosus+_ (Figs. 2, 3, 5).--The origin from the
extreme posterior edge of the posterior iliac crest of the ilium is
fleshy and is aponeurotic from the last vertebra of the synsacrum and
the transverse processes of several caudal vertebrae. The straplike
belly passes along the posterolateral margin of the thigh. Immediately
posterior to the knee, the muscle is divided transversely by a
ligament. That portion passing anteriorly from the ligament is the _m.
accessorius semitendinosi_ (here considered a part of the _m.
semitendinosus_) and is discussed below. The ligament continues
distally in two parts; one part inserts on the medial surface of the
_pars media_ of the _m. gastrocnemius_ and the other part fuses with
the tendon of insertion of the _m. semimembranosus_.
The _m. accessorius semitendinosi_ extends anteriorly from the above
mentioned ligament to a fleshy insertion on the posterolateral surface
of the femur immediately proximal to the condyles.
Action.--Moves femur posteriorly, flexes the crus and aids in
extending the tarsometatarsus.
Comparison.--No significant differences noted among the species
studied.
_+Musculus semimembranosus+_ (Figs. 3, 4, 5).--This straplike muscle
passes along the posteromedial surface of the thigh. The origin is
semitendinous along a line on the ischium, from a point dorsal to the
middle of the ischiopubic fenestra to the posterior end of the
ischium, and from a small area of the abdominal musculature posterior
to the ischium. The insertion is by means of a broad, thin tendon on a
ridge on the medial surface of the tibia immediately distal to the
head of this bone. The tendon of insertion passes between the head of
the _pars media_ and _pars interna_ of the _m. gastrocnemius_ and is
fused with the tendon of the _m. semitendinosus_.
Action.--Flexes crus.
Comparison.--No significant differences noted among the species
studied.
_+Musculus biceps femoris+_ (Fig. 2).--Long, thin, and somewhat
triangular, this muscle lies on the lateral side of the thigh just
underneath the _m. iliotibialis_. Its origin is from a line along the
anterior and posterior iliac crests underneath the origin of the _m.
iliotibialis_. Anterior to the acetabulum the origin is aponeurotic,
and the edge of this aponeurosis passes over the proximal end of the
femur. The origin posterior to the acetabulum is fleshy. The most
anterior point of origin is difficult to ascertain but it lies near
the center of the anterior iliac crest. The most posterior point of
origin is immediately dorsal to the posterior end of the ilioischiatic
fenestra. Behind the knee the fibers of this muscle converge to form
the strong tendon of insertion which passes through the biceps loop,
under the tendon of origin of the _m. flexor perforatus digiti II_,
and inserts on a small tubercle on the posterolateral edge of the
fibula at the point of the tibia-fibula fusion.
The biceps loop is tendinous and the distal end attaches to a
protuberance on the posterolateral edge of the femur at the proximal
edge of the external condyle. The proximal end attaches to the
anterolateral edge of the femur immediately proximal to the distal end
of the loop, which extends posterior to the femur. The distal arm of
this loop is connected with the tendon of origin of the _m. flexor
perforatus digiti II_ by a strong tendon.
Action.--Flexes crus.
Comparison.--No significant differences noted among the species
studied.
_+Musculus ischiofemoralis+_ (Fig. 3).--Short and thick, this muscle
arises directly from the lateral surface of the ischium between the
posterior iliac crest and the ischiopubic fenestra. The area of origin
extends to the posterior edge of the ischium. The insertion is
tendinous on the lateral surface of the trochanter opposite the
insertion of the _m. iliotrochantericus medius_.
Action.--Moves femur posteriorly and rotates it in this direction.
Comparison.--No significant differences noted among the species
studied.
_+Musculus obturator internus+_ (Figs. 4, 7).--Lying on the inside of
the pelvis and covering the medial surface of the ischiopubic
fenestra, is this flat, pinnate, leaf-shaped muscle. The origin is
fleshy and is from the ischium and pubis around the edges of this
fenestra; none of the fibers arises from the membrane stretched across
the fenestra. Anteriorly the fibers converge and form a strong tendon
that passes through the obturator foramen and inserts on the
posterolateral surface of the trochanter of the femur.
Action.--Rotates femur posteriorly.
Comparison.--No significant differences noted among the species
studied.
_+Musculus obturator externus+_ (Fig. 7).--Short and fleshy, this
muscle consists of two parts which are not easily separable but which
may be traced throughout its length. The parts are more nearly
distinct at the origin. The dorsal part arises directly from the
ischium along the dorsal edge of the obturator foramen. The larger
ventral part arises directly from the anterior and ventral edges of
the obturator foramen. The fibers of the dorsal part pass anteriorly,
cover the tendon of the _m. obturator internus_ laterally, and insert
on the trochanter around the point of insertion of the latter muscle.
The fibers of the ventral part pass parallel with the tendon of the
_m. obturator internus_ and insert on the trochanter immediately
distal and posterior to the tendon of the latter muscle.
Action.--Rotates femur posteriorly.
Comparison.--In _Passer_, _Estrilda_, _Poephila_, _Hesperiphona_,
_Carpodacus_, _Pinicola_, _Leucosticte_, _Spinus_ and _Loxia_, this
muscle is undivided and, in its position, origin, and insertion,
resembles the ventral part of the bipartite muscle described above.
The origin is from the anterior and ventral edges of the obturator
foramen and the insertion is on the trochanter of the femur
immediately distal and posterior to the insertion of the _m. obturator
internus_. In all other genera examined, the muscle is bipartite. In
_Chlorura_ the dorsal part is larger and better developed than it is
in the other genera.
_+Musculus adductor longus et brevis+_ (Figs. 3, 4, 5).--Consisting of
two distinct, straplike parts, this large muscle lies on the medial
surface of the thigh, posterior to the femur.
The _pars anticus_ has a semitendinous origin on a line that extends
posteriorly from the posteroventral edge of the obturator foramen to a
point half way across the membrane that covers the ischiopubic
fenestra. The insertion is fleshy along the posterior surface of the
femur from the level of the insertion of the _m. piriformis_ distally
to the medial surface of the internal condyle.
The _pars posticus_ originates by a broad, flat tendon on a line
across the posterior half of the membrane that covers the ischiopubic
fenestra. The insertion is at the point of origin of the _pars media_
of the _m. gastrocnemius_ on the posteromedial surface of the proximal
end of the internal condyle of the femur. There is a broad tendinous
connection with the proximal end of the _pars media_ of the _m.
gastrocnemius_. The anterior edge of the _pars posticus_ is overlapped
medially by the posterior edge of the _pars anticus_.
Action.--Flexes thigh; may flex crus also and may extend
tarsometatarsus.
Comparison.--In _Vireo olivaceous_, the origin of this muscle does not
extend the length of the ischiopubic fenestra. The origin,
furthermore, is along the dorsal edge of the ischiopubic fenestra and
not from the membrane covering the fenestra. Finally, in this species,
the origin of the _pars posticus_ is fleshy.
_+Musculus tibialis anticus+_ (Figs. 2, 5).--Lying along the anterior
edge of the crus, a part of this muscle is covered by the _m. peroneus
longus_. The origin is by two distinct heads, each of which is
pinnate. The anterior head arises directly from the edges of the outer
and inner cnemial crests. The posterior head arises by a short, strong
tendon from a small pit on the anterodistal edge of the external
condyle of the femur. This tendon and the proximal end of the muscle
pass between the head of the fibula and the outer cnemial crest. The
two heads of the muscle fuse at a place slightly more than one-half of
the distance down the crus. At the distal end of the crus this muscle
gives rise to a strong tendon which passes under a fibrous loop
immediately proximal to the external condyle in company with the _m.
extensor digitorum longus_ and which passes between the condyles of
the tibia and inserts on a tubercle on the anteromedial edge of the
proximal end of the tarsometatarsus.
Action.--Flexes tarsometatarsus.
Comparison.--No significant differences noted among the species
studied.
_+Musculus extensor digitorum longus+_ (Figs. 3, 5, 8).--Slender and
pinnate, this muscle lies along the anteromedial surface of the tibia.
The origin is fleshy from most of the region between the cnemial
crests and from a line along the anterior surface of the proximal
fourth of the tibia. Approximately two-thirds of the distance down the
crus the muscle gives rise to the tendon of insertion which passes
through the fibrous loop near the distal end of the tibia in company
with the _m. tibialis anticus_. The tendon then passes along beneath
the supratendinal bridge at the distal end of the tibia, traverses the
anterior intercondylar fossa, and passes beneath a bony bridge on the
anteromedial surface of the proximal end of the tarsometatarsus. The
tendon continues along the anterior surface of the tarsometatarsus to
a point immediately above the bases of the toes and there gives rise
to three branches, one to the anterior surface of each foretoe. The
insertions of each branch are on the anterior surfaces of the
phalanges as shown in Fig. 8.
Action.--Extends foretoes.
Comparison.--This muscle is weakly developed in _Leucosticte_ and
_Calvarius_; the belly is slender and extends only half way down the
crus before giving rise to the tendon of insertion. The functional
significance of this variation is difficult to understand. The
convergence in muscle pattern shown by these two genera, however, is
in all probability the result of similarities in behavior patterns.
These birds perch less frequently than do the other birds studied.
Thus, the toes are neither flexed nor extended as often; the smaller
size of the _m. extensor digitorum longus_ may have resulted in part
from this lessened activity. Except for the variations just noted,
there are no significant differences among the species studied; even
the rather complex patterns of insertion are identical.
_+Musculus peroneus longus+_ (Fig. 1).--Relatively thin and straplike,
this muscle lies on the anterolateral surface of the crus and is
intimately attached to the underlying muscles. The part of the origin
from the proximal edges of the inner and outer cnemial crests is
semitendinous but the part of the origin from the lateral edge of the
shaft of the fibula is tendinous. Approximately two-thirds the
distance down the crus the muscle gives rise to the tendon of
insertion. Immediately above the external condyle of the tibiotarsus
this tendon divides. The posterior branch inserts on the proximal end
of the lateral edge of the tibial cartilage. The anterior branch
passes over the lateral surface of the external condyle to the
posterior surface of the tarsometatarsus and there unites with the
tendon of the _m. flexor perforatus digiti III_.
Action.--Extends tarsometatarsus and flexes third digit.
Comparison.--No significant differences noted among the species
studied.
_+Musculus peroneus brevis+_ (Figs. 2, 3).--Lying along the
anterolateral surface of the tibia, this slender, pinnate muscle
arises from a fleshy origin along this surface and along the anterior
surface of the fibula from a point immediately proximal to the
insertion of the _m. biceps femoris_ to a point approximately
two-thirds of the way down the crus. Near the distal end of the tibia
the muscle gives rise to the tendon of insertion that passes through a
groove on the anterolateral edge of the tibia just above the external
condyle. Here the tendon is held in place by a broad fibrous loop and
passes under the anterior branch of the tendon of insertion of the _m.
peroneus longus_ and inserts on a prominence on the lateral edge of
the proximal end of the tarsometatarsus.
Action.--Extends tarsometatarsus and may abduct it slightly.
Comparison.--No significant differences noted among the species
studied.
_+Musculus gastrocnemius+_ (Figs. 1, 4).--The largest muscle of the
pelvic appendage, it covers superficially all of the posterior
surface, most of the medial surface, and half of the lateral surface
of the crus. The muscle originates by three distinct heads.
The _pars externa_ covers the posterolateral surface of the crus, is
intermediate in size between the other two heads, and arises by a
short, strong tendon from a small bony protuberance on the
posterolateral side of the distal end of the femur immediately
proximal to the fibular condyle. The tendon is intimately connected
with the distal arm of the loop for the _m. biceps femoris_.
The _pars media_ is the smallest of the three heads and lies on the
medial surface of the crus. The head of the _pars media_ is separated
from the _pars interna_ by the tendon of insertion of the _m.
semimembranosus_ and originates by a short, strong tendon from the
posteromedial surface of the proximal end of the internal condyle of
the femur. The proximal portion of the _pars media_ has tendinous
connections with the tendon of the _m. semitendinosus_ and with the
_pars posticus_ of the _m. adductor longus et brevis_.
The _pars interna_ is the largest of the three heads and covers most
of the medial surface of the crus. This head in its proximal portion
is distinctly divided into anterior and posterior parts, the former
overlapping the latter medially. The origin of the posterior part is
fleshy from the anterior half of the tibial head. Some of the fibers
of the anterior part arise directly from the inner cnemial crest while
its remaining fibers arise from the patellar tendon (Fig. 1) and form
a band that extends around the anterior surface of the knee, covering
the insertion of the _m. sartorius_.
Approximately half way down the crus, the three heads give rise to the
tendon of insertion, the _tendo achillis_, which passes over and is
tightly bound to the posterior surface of the tibial cartilage. The
insertion is tendinous on the posterior surface of the hypotarsus and
along the posterolateral ridge of the tarsometatarsus. This tendon
seems to be continuous with a fascia which forms a sheath around the
posterior surface of the tarsometatarsus holding the other tendons of
this region firmly in the posterior sulcus.
Action.--Extends tarsometatarsus.
Comparison.--Study of the _pars externa_ and _pars media_ reveals no
significant differences among the species dissected. The _pars
interna_, however, is subject to some variation which is described
below.
_Pars interna_ bipartite
_Vireo_ _Chlorura_
_Seiurus_ _Pipilo_
_Icterus_ _Calamospiza_
_Molothrus_ _Chondestes_
_Piranga_ _Junco_
_Richmondena_ _Spizella_
_Guiraca_ _Zonotrichia_
_Passerina_ _Passerella_
_Spiza_ _Calcarius_
The two parts of the _m. gastrocnemius_ are most distinct in _Vireo_.
_Icterus_, _Molothrus_, _Richmondena_, _Guiraca_, and _Passerina_ lack
the fibrous band that passes around the front of the knee. In _Spiza_
this band of fibers is smaller than in the other species.
_Pars interna_ undivided
_Passer_ _Pinicola_
_Estrilda_ _Leucosticte_
_Poephila_ _Spinus_
_Hesperiphona_ _Loxia_
_Carpodacus_
In _Leucosticte_, although the _pars interna_ is undivided, there is a
band of fibers which extends around the front of the knee (see
discussion, p. 183).
_+Musculus plantaris+_ (Fig. 5).--Small and slender, this muscle lies
on the posteromedial surface of the crus, beneath the _pars interna_
of the _m. gastrocnemius_ and originates by fleshy fibers from the
posteromedial surface of the proximal end of the tibia immediately
distal to the internal articular surface. The belly extends
approximately one-sixth of the way down the crus and gives rise to a
long, slender tendon that inserts on the proximomedial edge of the
tibial cartilage.
Action.--Extends tarsometatarsus.
Comparison.--No significant differences noted among the species
studied.
_+Musculus flexor perforatus digiti II+_ (Figs. 3, 9).--This is a
slender muscle which lies on the lateral side of the crus beneath the
_pars externa_ of the _m. gastrocnemius_ and is intimately connected
anteromedially with the _m. flexor digitorum longus_ and
posteromedially with the _m. flexor hallucis longus_. The origin is by
a strong tendon from the lateral surface of the external condyle of
the femur at the point of origin of the _m. flexor perforans et
perforatus digiti II_. This tendon serves also as the origin of the
anterior head of the _m. flexor hallucis longus_. The tendon connects
also by a broad tendinous band with the distal arm of the loop for the
_m. biceps femoris_ and by a similar band with the lateral edge of the
fibula immediately distal to the head. The tendon of insertion passes
distally, perforates the tibial cartilage near its lateral edge,
traverses the middle medial canal of the hypotarsus (Fig. 6), and
passes distally to the foot. At the distal end of the tarsometatarsus
the tendon is held against the medial surface of the first metatarsal
by a straplike sheath. The tendon then passes over a sesamoid bone
between the first metatarsal and the base of the second digit and is
bound to this bone by a sheath. The tendon inserts mainly along the
posteromedial edge of the proximal end of the first phalanx of the
second digit, although the termination is sheathlike and covers the
entire posterior surface of this phalanx. This sheathlike termination
is perforated by the tendons of the _m. flexor perforans et perforatus
digiti II_ and the branch of the _m. flexor digitorum longus_ that
inserts on the second digit.
Action.--Flexes second digit.
Comparison.--In _Vireo_ this muscle is larger and more deeply situated
than it is in the other species examined and has no connection with
the _m. flexor hallucis longus_.
_+Musculus flexor perforatus digiti III+_ (Fig. 5).--Long and
flattened, this muscle lies on the posteromedial side of the crus
beneath the _m. gastrocnemius_. The belly is tightly fused laterally
with the belly of the _m. flexor hallucis longus_ and posteriorly with
the belly of the _m. flexor perforatus digiti IV_. The origin is by a
long, strong tendon from a small tubercle just medial to, and at the
proximal end of, the external condyle of the femur. Below the middle
of the crus this muscle terminates in a strong tendon which perforates
the tibial cartilage near its lateral edge. In this region the tendon
is sheathlike and wrapped around the tendon of the _m. flexor
perforatus digiti IV_. These two tendons together pass through the
posterolateral canal of the hypotarsus (Fig. 6). Immediately distal to
the hypotarsus the two tendons separate, and the tendon of the _m.
flexor perforatus digiti III_ receives a branch of the tendon of the
_m. peroneus longus_. The tendon passes distally over the surface of
the second trochlea, and its insertion is sheathlike on the posterior
surface of the first phalanx, and on the proximal end of the second.
In the area of insertion this tendon is perforated by that of the _m.
flexor perforans et perforatus digiti III_ and by that of the _m.
flexor digitorum longus_ to the third digit.
Action.--Flexes digit III.
Comparison.--In _Passer_, _Estrilda_, _Poephila_, _Hesperiphona_,
_Carpodacus_, _Pinicola_, _Leucosticte_, _Spinus_, and _Loxia_ the
edges of the sheathlike tendon are thickened at the points of
insertion, so that the tendon appears to have two branches which
insert along the posterolateral edges of the first phalanx and are
connected medially by a fascia.
_+Musculus flexor perforatus digiti IV+_ (Fig. 3).--Extending along
the posterior edge of the crus, this slender muscle lies beneath the
_m. gastrocnemius_. The belly is fused with those of the _m. flexor
hallucis longus_ and _m. flexor perforatus digiti III_. Its origin is
fleshy from the intercondyloid region of the distal end of the femur
and has a few fibers arising from the tendon of origin of the _m.
flexor perforatus digiti III_. Near the distal end of the crus the
muscle gives rise to the strong tendon of insertion which perforates
the tibial cartilage near its lateral edge and in this region is
ensheathed by the tendon of the _m. flexor perforatus digiti III_. The
two tendons pass together through the posterolateral canal of the
hypotarsus (Fig. 6). The tendon continues distally along the
tarsometatarsus and the posterior surface of digit IV. The tendon
bifurcates at approximately the middle of the first phalanx. A short
lateral branch inserts on the posterolateral edge of the proximal end
of the second phalanx. The long medial branch is perforated by a
branch of the _m. flexor digitorum longus_; the distal end is
flattened, has thickened edges, and inserts over the posterior
surfaces of the distal end of the second phalanx, and over the
proximal end of the third phalanx.
Action.--Flexes digit IV.
Comparison.--No significant differences noted among the species
studied.
_+Musculus flexor perforans et perforatus digiti II+_ (Figs. 2,
9).--Small and spindle-shaped, this muscle lies on the posterolateral
side of the crus immediately beneath the _pars externa_ of the _m.
gastrocnemius_. The origin is fleshy and arises in company with the
_m. flexor perforans et perforatus digiti III_ from a point on the
posterolateral surface of the distal end of the femur between the
point of origin of the _pars externa_ of the _m. gastrocnemius_ and
the fibular condyle. The belly extends approximately one-fourth of the
way down the crus and gives rise to the tendon of insertion which
passes distally and superficially through the posterior edge of the
tibial cartilage. The tendon traverses the posteromedial canal of the
hypotarsus (Fig. 6) and continues along the posterior surface of the
tarsometatarsus. Between the first metatarsal and the base of the
second digit the tendon is enclosed by the medial surface of a
sesamoid bone. This tendon then perforates that of the _m. flexor
perforatus digiti II_ at the level of the first phalanx and in turn is
perforated by the tendon of the _m. flexor digitorum longus_ at the
proximal end of the second phalanx. The insertion is on the posterior
surface of the second phalanx.
Action.--Flexes digit II.
Comparison.--In _Passer_, _Estrilda_, _Poephila_, _Hesperiphona_,
_Carpodacus_, _Pinicola_, _Leucosticte_, _Spinus_, and _Loxia_ the
proximal portion of this muscle is more intimately connected with the
posterior edge of the _m. flexor perforans et perforatus digiti III_
than it is in the other species examined.
_+Musculus flexor perforans et perforatus digiti III+_ (Fig. 2).--Long
and pinnate, this muscle lies on the lateral surface of the crus
beneath the _m. peroneus longus_ and _pars externa_ of the _m.
gastrocnemius_. There are two distinct heads. The origin of the
anterior head is fleshy from the proximal edge of the outer cnemial
crest and from the internal edge of the distal end of the patellar
tendon. The posterior head arises by a tendon from the femur in
company with the _m. flexor perforans et perforatus digiti II_, is
connected also with the tendon of origin of the _m. flexor perforatus
digiti II_, and is loosely attached to the head of the fibula. Fibers
from the belly of the muscle attach throughout its length to the
lateral edge of the fibula, and the muscle is tightly fused also with
adjacent muscles. The tendon of insertion is formed approximately
one-half the way down the crus. The tendon perforates the posterior
surface of the tibial cartilage and passes through the posteromedial
canal of the hypotarsus (Fig. 6). At the base of the third digit the
tendon ensheathes that of the _m. flexor digitorum longus_ and the two
together perforate the tendon of the _m. flexor perforatus digiti
III_. Immediately distal to this perforation the tendon of the _m.
flexor perforans et perforatus digiti III_ ceases to ensheath that of
the _m. flexor digitorum longus_. The latter passes beneath that of
the former. Near the distal end of the second phalanx the tendon of
the _m. flexor digitorum longus_ perforates that of the _m. flexor
perforans et perforatus digiti III_. The latter inserts on the
posterior surface of the distal end of the second phalanx and the
proximal end of the third.
Action.--Flexes digit III.
Comparison.--In _Passer_, _Estrilda_, and _Poephila_, and in all the
cardueline finches examined the proximal portion of this muscle is
more intimately connected with the anterior edge of the _m. flexor
perforans et perforatus digiti II_ than it is in the other species
examined.
_+Musculus flexor digitorum longus+_ (Figs. 3, 5).--This strong,
pinnate muscle is deeply situated along the posterior surfaces of the
tibia and fibula. There are two distinct heads of origin. The lateral
head arises by means of fleshy fibers from the posterior edge of the
head of the fibula. The medial head arises by means of fleshy fibers
from the region under the ledgelike external and internal articular
surfaces of the proximal end of the tibia. Neither head has any
connection with the femur in contrast to the condition, described by
Hudson (1937: 46-47) in the crow, _Corvus brachyrhynchos_, and in the
raven, _Corvus corax_. Near the point of insertion of the _m. biceps
femoris_ the two heads fuse. The common belly is attached by fleshy
fibers to the posterior surface of the tibia and fibula for two-thirds
of the distance down the crus. Near the distal end of the crus the
muscle terminates in a strong tendon which passes deeply through the
tibial cartilage and traverses the anteromedial canal of the
hypotarsus (Fig. 6). About midway down the tarsometatarsus this tendon
becomes ossified. Immediately above the bases of the toes it gives
rise to three branches, one to the posterior surface of each of the
foretoes. These branches perforate the other flexor muscles of the
toes as described in the accounts of those muscles and insert as
follows: The branch to digit II inserts on the base of the ungual
phalanx and by a stout, tendinous slip on the distal end of the second
phalanx (Fig. 9). The branch to digit III inserts on the base of the
distal end of the third phalanx and a stronger slip to the distal end
of the second or proximal end of the third. The branch to digit IV
inserts on the base of the ungual phalanx, with one tendinous slip to
the distal end of the third phalanx and another to the distal end of
the fourth.
Action.--Flexes foretoes.
Comparison.--No significant differences noted among the species
studied.