Fisher (1946), studying vultures, reports the following: tib_Variation in the Muscles and Nerves of the Leg in Two Genera of Grouse (Tympanuchus and Pedioecetes)

branches, in addition to the main sciatic branch, supplying M. extensor

iliofibularis (typically supplied by the peroneal nerve); an obturator

supply, in addition to the usual tibial supply, to M. flexor cruris

medialis; a tibial supply, in addition to the typical obturator supply,

to M. obturator pars postica; a possible obturator supply, in addition

to the typical femoral supply, to M. ambiens; a possible peroneal

supply, in addition to the typical tibial supply, to M. flexor digitorum

longus; and a peroneal supply to Mm. abductor digiti IV, flexor hallucis

brevis, and adductor digiti II (which are typically supplied by the

paraperoneal branch of the tibial nerve). Fisher's postfibular branch of

the peroneal nerve, which supplies the latter three muscles, apparently

represents the paraperoneal branch of the tibial nerve.

Carlsson (1884) did not find a femoral nerve supply for M. gluteus

profundus. He found an obturator supply, in addition to the usual

sciatic supply, to M. flexor ischiofemoralis in _Eudyptes chrysolopha_

and _Mergulus alle_ but not in the other two forms studied. He reported

a peroneal supply, rather than the expected tibial (paraperoneal)

supply, to Mm. abductor digiti IV and adductor digiti IV.

DeMan (1873) found a twig of the obturator nerve supplying M. flexor

ischiofemoralis, in addition to the typical innervation, in _Corvus

monedula_, but not in the few other forms studied. He did not

distinguish tibial and peroneal components in the thigh.

Wilcox (1948), studying a loon, did not find any peroneal supply to M.

extensor iliotibialis lateralis or to M. gluteus profundus. He found a

femoral, rather than a peroneal, supply to M. piriformis. He found an

obturator, instead of a tibial, supply to M. flexor ischiofemoralis. (In

some of my specimens I found a tiny blood vessel, appearing much like a

nerve, emerging from the obturator foramen and entering M. flexor

ischiofemoralis.) Wilcox reports an innervation of M. caudofemoralis

pars caudifemoralis from the pudendal plexus, in addition to the usual

sciatic one. Wilcox did not distinguish tibial and peroneal components

in the thigh. In the shank and foot he misidentified the peroneal nerve

as the tibial nerve and therefore gave erroneous innervations for all

the muscles supplied by this nerve, except for M. adductor digiti IV,

which actually should be supplied by the tibial nerve.

Howell (1938) studied only the hip and thigh musculature of the chicken.

He overlooked the femoral nerve supply for M. gluteus profundus.

Romer (1927) studied only the hip and thigh muscles of the chick. He did

not distinguish tibial and peroneal components in the thigh. He did not

mention any sciatic supply for M. gluteus profundus.

Appleton (1928), studied (in various birds) only those muscles of the

hip and thigh that are innervated by the tibial and peroneal nerves. He

terms the former "ischiadicus ventralis" and the latter "ischiadicus

dorsalis." His findings did not differ from mine.

Many differences in the innervation of specific muscles are reported in

the literature, even in the same species (by different workers). Some of

these differences may be real; others are probably misinterpretations.

Consequently more work needs to be done before a complete understanding

can be obtained of the innervation of the leg muscles of birds.

Especially needed are studies of the tibial-peroneal nerve relationship,

perhaps approached by a method other than gross dissection.

SUMMARY

The muscles and nerves were dissected in eight legs of the Lesser

Prairie Chicken (_Tympanuchus pallidicinctus_), six legs of the Greater

Prairie Chicken (_T. cupido pinnatus_), three legs of Attwater's Prairie

Chicken (_T. c. attwateri_), and six legs of the Sharp-tailed Grouse

(_Pedioecetes phasianellus jamesi_) for the purpose of obtaining

information on individual variation as well as variation between these

closely related species. Relatively little information is available

regarding the nerves of the leg of birds and little is known about

individual variation and variation between closely related forms in the

muscles of the leg of birds.

All osteological terms used in the present paper are defined and those

of the pelvis are illustrated. New terms were coined for some structures

for which no names could be found in the literature. Terms were also

coined for the major divisions of the femoral and sciatic nerves. With

three exceptions, my muscle terminology follows that of Fisher (1946)

and Fisher and Goodman (1955). Their term femoritibialis externus is not

used here; the muscle so named is considered to be a part of M. vastus

lateralis. Fisher's accessory head of M. flexor cruris lateralis is

considered to be a distinct muscle--M. femorocruralis. Usage of the term

obturator internus is avoided because the muscle so named is considered

not to be homologous with the mammalian muscle of the same name; the

entire obturator complex is called M. obturator, and is subdivided into

four parts.

The typical (most common) condition of the nerves and muscles in

_Tympanuchus pallidicinctus_ is described in detail. Variations from

this condition among the other birds studied are then described. All

muscles of one leg of _T. pallidicinctus_ are illustrated. Several

variations in the muscles are also illustrated. The lumbosacral plexus

and nerves of the leg in several specimens that show variations are

illustrated.

Considerable individual variation was found in both the muscles and the

nerves of the leg of the species studied. Certain muscles were more

variable than others. Mm. flexor digitorum longus, obturator,

caudofemoralis, and extensor hallucis longus showed the greatest number

of variations. Mm. vastus medialis, femoritibialis internus, flexor

perforatus digiti III, extensor brevis digiti III, and abductor digiti

IV did not exhibit any variations considered significant. Certain legs

showed a greater number of variations from the typical condition than

did others.

Although most of the variations were minor, some were major. M. extensor

proprius digiti III was present in two legs of _Pedioecetes_ but absent

in the other legs studied. A fleshy muscle slip connected M.

caudofemoralis pars caudifemoralis with the tendinous raphe between Mm.

flexor cruris lateralis and femorocruralis in two legs, whereas in

others this connection was tendinous or even absent altogether. M.

flexor cruris lateralis had an accessory slip arising from the caudal

musculature in one leg. A vinculum connected the insertional tendons of

Mm. flexor perforans et perforatus digiti II and flexor perforatus

digiti II in one leg.

In most specimens there was as much variation between the muscles of the

right and left legs of one individual as there was between individuals.

The same was true for the nerves, except for the lumbosacral plexus, in

which there was no significant variation between the right and left

sides of any individual. The peroneal and obturator nerves varied less

than the other nerves.

No constant differences in the muscles or nerves was found between _T.

cupido pinnatus_ and _T. c. attwateri_. One constant difference was

found between _T. cupido_ and _T. pallidicinctus_: the fleshy origin of

M. extensor iliotibialis lateralis in _T. cupido_ was thicker

(associated with a thicker edge of the lateral iliac process).

Although no constant differences in the nerves were found between

_Pedioecetes_ and _Tympanuchus_ (both species), 17 constant differences

in the muscles were found between these two genera. Study of additional

specimens possibly would show enough individual variation in some of

these differences to reduce the number of constant differences to fewer

than 17. Seven of these differences pertain to features of a single

muscle--M. flexor cruris medialis. Some of the other differences are

associated with the thinner and much less pronounced lateral iliac

process in _Pedioecetes_. The picture of the differences between

_Tympanuchus_ and _Pedioecetes_ that this study presents is radically

different from that presented by the study of Hudson, _et al._ (1959).

The important differences in innervation between previous studies and

the present one are discussed.

All of the muscles under consideration have been grouped as either

dorsal or ventral muscles, according to their embryonic origin, as

described by Romer (1927) and Wortham (1948). This grouping probably

represents accurately the phylogenetic origin of these muscles. The

dorsal muscles probably were originally supplied by dorsal nerves--the

femoral and peroneal--and the ventral muscles probably were originally

supplied by ventral nerves--the obturator and tibial. This primitive

muscle-nerve relationship has been relatively constant.

Several previous workers have reported some dorsal muscles supplied by

ventral nerves and _vice versa_. Those findings should be viewed with

suspicion until verified, because the proximal parts of the tibial and

peroneal nerves are intimately associated and their relationship is

easily misinterpreted. I found a branch of the tibial nerve that is

closely associated with, and distributed with, the peroneal nerve. That

branch of the tibial nerve has been mistakenly considered a part of the

peroneal nerve by some workers. My study revealed no definite exceptions

to the expected innervation.

TABLE 1. SYNONYMY OF THE MUSCLES OF THE LEG OF BIRDS

===============+===============+============+==============+==============

| | Howell | Fisher & |

Gadow (1891) | Hudson (1937) | (1938) |Goodman (1955)| Holmes

---------------+---------------+------------+--------------+--------------

ilio-tibialis |ilio-tibialis |extensor |extensor |extensor

| | iliotibia- | ilio-tibia- | iliotibialis

| | lis latera-| lis | lateralis

| | lis | lateralis |

---------------+---------------+------------+--------------+--------------

ilio-tibialis |sartorius |extensor |extensor |extensor

internus s. | |iliotibialis| ilio-tibia- | iliotibialis

sartorius | |anterior | lis anterior| anticus

---------------+---------------+------------+--------------+--------------

ambiens |ambiens |ambiens |ambiens |ambiens

---------------+---------------+------------+--------------+--------------

femori-tibialis| | |femoritibialis|vastus

externus | | | externus | lateralis

| | | |(a) pars

| | | | postica

---------------+ | +--------------+

{|femori-tibialis|vastus |vastus |(b) pars

femori- {| externus | lateralis | lateralis | lateralis

tibialis {+---------------+------------+--------------+--------------

medius {|femori-tibialis|} {|vastus |vastus

{| medius |} {| medialis | medialis

---------------+---------------+}vastus {+--------------+--------------

femori-tibialis|femori-tibialis|} medialis{|femoritibialis|femoritibialis

internus | internus |} {| internus | internus

---------------+---------------+------------+--------------+--------------

ilio-fibularis |biceps femoris |extensor |extensor |extensor

| | iliofibu- | ilio- | ilio-

| | laris | fibularis | fibularis

---------------+---------------+------------+--------------+--------------

ilio-femoralis |glutaeus medius|piriformis |piriformis |piriformis

externus | et minimus | | |

---------------+---------------+------------+--------------+--------------

ilio-trochante-|ilio-trochante-|gluteus |gluteus |gluteus

ricus | ricus | profundus | profundus | profundus

posterior | posterior | | |

---------------+---------------+------------+--------------+--------------

ilio-trochante-|ilio-trochante-|iliacus |iliacus |iliacus

ricus | ricus | | |

anterior | anterior | | |

---------------+---------------+------------+--------------+--------------

ilio-trochante-|ilio-trochante-| |ilio-trochan- |iliotrochante-

ricus medius | ricus medius | | tericus | ricus medius

| | | medius |

---------------+---------------+------------+--------------+--------------

ilio-trochante-|iliacus |psoas |psoas |psoas

ricus | | | |

internus | | | |

---------------+---------------+------------+--------------+--------------

caud-ilio- |semitendinosus |flexor |flexor cruris |flexor cruris

flexorius | | cruris | lateralis | lateralis

| | lateralis |(a) main head |

---------------+---------------+------------+ +--------------

accessorius |accessorius |femorocru- |(b) accessory |femorocruralis

semitendinosi| semitendinosi| ralis | heads |

---------------+---------------+------------+--------------+--------------

ischio- |semimembranosus|flexor |flexor cruris |flexor cruris

flexorius | | cruris | medialis | medialis

| | medialis | |

---------------+---------------+------------+--------------+--------------

caud-ilio- |piriformis | |caudofemoralis|caudofemoralis

femoralis | | | |

(a) pars |(a) pars |caudofemo- |(a) pars |(a) pars

caudi- | caudi- |ralis | caudi- | caudifemo-

femoralis | femoralis | | femoralis | ralis

| +------------+ |

(b) pars ilio- |(b) pars ilio- |flexor ilio-|(b) pars ilio-|(b) pars

femoralis | femoralis | femoralis | femoralis | iliofemo-

| | | | ralis

---------------+---------------+------------+--------------+--------------

ischio- |ischio- |flexor |flexor ischio-|flexor

femoralis | femoralis | ischiofe- | femoralis | ischiofemo-

| | moralis | | ralis

---------------+---------------+------------+--------------+--------------

{|adductor longus|adductor |adductor |adductor

{| et brevis | superfi- | superfici- | superficialis

{|(a) pars | cialis | alis |

pub-ischio- {| anterior | | |

femoralis {| +------------+--------------+--------------

{|(b) pars |adductor |adductor |adductor

{| posterior | profundus | profundus | profundus

---------------+---------------+------------+--------------+--------------

obturator |obturator |} {|obturator |}

| internus |} {| internus |}

---------------+---------------+} obturator{+--------------+} obturator

accessorii M. |obturator |} {|obturator |}

obturatoris | externus |} {| externus |}

---------------+---------------+------------+--------------+--------------

gastrocnemius |gastrocnemius | |gastrocnemius |gastrocnemius

---------------+---------------+------------+--------------+--------------

flexor |flexor | |flexor perfo- |flexor perfo-

perforans et | perforans et | | rans et per-| rans et per-

perforatus | perforatus | | foratus | foratus

digiti II | digiti II | | digiti II | digiti II

---------------+---------------+------------+--------------+--------------

flexor |flexor | |flexor perfo- |flexor perfo-

perforans et | perforans et | | rans et per-| rans et per-

perforatus | perforatus | | foratus | foratus

digiti III | digiti III | | digiti III | digiti III

---------------+---------------+------------+--------------+--------------

flexor |flexor | |flexor |flexor perfo-

perforatus | perforatus | | perforatus | ratus digiti

digiti IV | digiti IV | | digiti IV | IV

---------------+---------------+------------+--------------+--------------

flexor |flexor | |flexor |flexor perfo-

perforatus | perforatus | | perforatus | ratus

digiti III | digiti III | | digiti III | digiti III

---------------+---------------+------------+--------------+--------------

flexor |flexor | |flexor |flexor perfo-

perforatus | perforatus | | perforatus | ratus digiti

digiti II | digiti II | | digiti II | II

---------------+---------------+------------+--------------+--------------

flexor hallucis|flexor hallucis| |flexor hallu- |flexor hallu-

longus | longus | | cis longus | cis longus

---------------+---------------+------------+--------------+--------------

plantaris |plantaris | |plantaris |plantaris

---------------+---------------+------------+--------------+--------------

flexor |flexor | |flexor digi- |flexor digito-

profundus | digitorum | | torum longus| rum longus

s. perforans | longus | | |

---------------+---------------+------------+--------------+--------------

popliteus |popliteus | |popliteus |popliteus

---------------+---------------+------------+--------------+--------------

peroneus |peronaeus | |peroneus |peroneus

superficialis| longus | | longus | longus

---------------+---------------+------------+--------------+--------------

tibialis |tibialis | |tibialis |tibialis

anticus | anterior | | anterior | anticus

---------------+---------------+------------+--------------+--------------

extensor |extensor | |extensor |extensor

digitorum | digitorum | | digitorum | digitorum

communis | longus | | longus | longus

---------------+---------------+------------+--------------+--------------

peroneus |peronaeus | |peroneus |peroneus

profundus | brevis | | brevis | brevis

---------------+---------------+------------+--------------+--------------

extensor |extensor | |extensor |extensor

hallucis | hallucis | | hallucis | hallucis

brevis | longus | | longus | longus

---------------+---------------+------------+--------------+--------------

abductor |abductor | |abductor |abductor

digiti II | digiti II | | digiti II | digiti II

---------------+---------------+------------+--------------+--------------

extensor brevis|} {| |extensor |extensor bre-

digiti III |} extensor {| | brevis | vis digiti

|} {| | digiti III | III

---------------+} proprius {+------------+--------------+--------------

extensor |} digiti {| |extensor |extensor

proprius |} III {| | proprius | proprius

digiti III |} {| | digiti III | digiti III

---------------+---------------+------------+--------------+--------------

extensor brevis|extensor brevis| |extensor |extensor bre-

digiti IV | digiti IV | | brevis | vis digiti

| | | digiti IV | IV

---------------+---------------+------------+--------------+--------------

flexor brevis |lumbricalis | | |lumbricalis

digiti III | | | |

---------------+---------------+------------+--------------+--------------

abductor |abductor | |abductor |abductor

digiti IV | digiti IV | | digiti IV | digiti IV

---------------+---------------+------------+--------------+--------------

flexor hallucis|flexor hallucis| |flexor |flexor hallu-

brevis | brevis | | hallucis | cis brevis

| | | brevis |

---------------+---------------+------------+--------------+--------------

adductor |adductor | |adductor |

digiti II | digiti II | | digiti II |

---------------+---------------+------------+--------------+--------------

adductor |adductor | | |

digiti IV | digiti IV | | |

---------------+---------------+------------+--------------+--------------

TABLE 2. RELATIVE SIZES (IN PERCENTAGES) OF SOME MUSCLES IN TYMPANUCHUS

AND PEDIOECETES

===========================+=======================+======================

| _Tympanuchus_ | _Pedioecetes_

Muscle +-----+---------+-------+------+--------+------

| Ave.| Range | No.[1]| Ave. | Range |No.[1]

---------------------------+-----+---------+-------+------+--------+------

of ilium) | .10 | .08-.11 | 13 | .19 | .17-.19| 6

---------------------------+-----+---------+-------+------+--------+------

of ilium) | .22 | .19-.27 | 13 | .31 | .27-.36| 6

---------------------------+-----+---------+-------+------+--------+------

by length of ilium) | .11 | .08-.16 | 13 | .22 | .19-.23| 6

---------------------------+-----+---------+-------+------+--------+------

tibiotarsus) | .09 | .08-.13 | 13 | .17 | .15-.17| 4

---------------------------+-----+---------+-------+------+--------+------

by length of ilium) | .20 | .17-.23 | 13 | .13 | .10-.16| 5

---------------------------+-----+---------+-------+------+--------+------

of femur) | .59 | .55-.63 | 13 | .40 | .38-.43| 6

---------------------------+-----+---------+-------+------+--------+------

tibiotarsus) | .73 | .64-.83 | 13 | .59 | .50-.62| 4

---------------------------+-----+---------+-------+------+--------+------

FOOTNOTES:

[Footnote 1: No. = number of legs.]

TABLE 3. OCCURRENCE OF INDIVIDUAL VARIATIONS IN MUSCLES

Variation in the Muscles and Nerves of the Leg in Two Genera of Grouse (Tympanuchus and Pedioecetes) · 第 10 / 11 段

Fisher (1946), studying vultures, reports the following: tibial