Part 1 (1/2)
Variation in the Muscles and Nerves of the Leg in Two Genera of Grouse (Tympanuchus and Pedioecetes).
by E. Bruce Holmes.
INTRODUCTION
The purposes of this study were: (1) to obtain information on individual variation in the anatomy of the muscles and nerves of the leg of _Tympanuchus cupido pinnatus_ (Greater Prairie Chicken), _T. c.
att.w.a.teri_ (Att.w.a.ter's Prairie Chicken), _T. pallidicinctus_ (Lesser Prairie Chicken), and _Pedioecetes phasianellus jamesi_ (Sharp-tailed Grouse); (2) to determine whether or not the two species of the genus _Tympanuchus_ differ constantly in the myology of the leg; and (3) to determine what constant differences in the myology of the leg exist between the two closely related genera _Tympanuchus_ and _Pedioecetes_.
These particular birds were chosen because they are closely related, and closely resemble one another in habitats occupied and in patterns of behavior. It was desired to study examples that showed as few adaptive differences as possible among the grouse. Series of each of the three species of grouse were readily obtainable, making it possible to draw comparisons at the level of individuals, subspecies, species, and genera.
The study here reported on was begun in the spring of 1957 and was completed in the autumn of 1961.
Prior work on the muscles of the leg of birds has been reviewed by Hudson (1937) and Hudson, _et al._ (1959). Only papers dealing with the innervation of the leg in birds are reviewed below.
DeMan (1873) treated the nerves of _Paradisea papuana_, _Corvus monedula_, and the chicken; he also commented briefly on a few other species. Jhering (Ihering, 1873) briefly described the lumbosacral plexus in approximately a dozen birds, but ill.u.s.trated only two. Gadow (1880) described the nerves in _Struthio_, _Rhea_, and _Casuarius_; his paper contains some excellent ill.u.s.trations of nerves. Unfortunately, the text is marred by numerous confusing typographical errors. Carlsson (1884) described the nerves of _Eudyptes chrysolopha_, _Alca torda_, _Mergulus alle_, and _Mormon arcticus_. Gadow (1891) described the nerves in a study that included a large variety of birds, but published few ill.u.s.trations.
DuToit (1913) described the lumbosacral plexus of the chicken.
Romer (1927) gave the innervation of the hip and thigh muscles in the chicken, but did not cover the lumbosacral plexus. Appleton (1928) gave the innervation, in various birds, only of those muscles of the hip and thigh that are supplied by the tibial and peroneal nerves; he did not include the lumbosacral plexus.
Sudilovskaya (1931) described the nerves of _Struthio_, _Rhea_, and _Dromaeus_ (_Dromiceius_). Unfortunately, his ill.u.s.trations are almost useless as far as the nerves are concerned. Boas (1933) described the lumbosacral plexus in a large number of birds. His extensive account includes numerous good ill.u.s.trations. Howell (1938) listed the innervation of the hip and thigh muscles in the chicken; he did not include the lumbosacral plexus. Fisher (1946) listed the innervation of the muscles of vultures, but did not include the lumbosacral plexus. Wilc.o.x (1948) gave the innervation of the muscles of _Gavia immer_, but did not include the lumbosacral plexus. Fisher and Goodman (1955) described the nerves in the Whooping Crane. Papers by Chomiak (1950) and Yasuda, _et al._ (1959), both dealing with the chicken, were not examined.
MATERIALS AND METHODS
Complete dissections of the muscles and nerves were made in eight legs (of five specimens) of the Lesser Prairie Chicken (_Tympanuchus pallidicinctus_), six legs (of four specimens) of the Greater Prairie Chicken (_T. cupido pinnatus_), three legs (of two specimens) of Att.w.a.ter's Prairie Chicken (_T. cupido att.w.a.teri_), and six legs (of four specimens) of the Sharp-tailed Grouse (_Pedioecetes phasianellus jamesi_).
For convenience and simplicity of reference, each specimen has been designated by a symbol consisting of the first letter of the genus and of the species (and also of the subspecies in _T. cupido_) plus a number. The letter ”L” or ”R” is added to indicate the left or right leg. Thus the symbol T.p. 1L refers to the left leg of specimen number one of _T. pallidicinctus_.
All specimens are in the University of Kansas Museum of Natural History.
The catalogue number of each specimen, and the legs of it that were dissected, are listed below.
T.p. 1L,R KU38520 T.c.p. 4L KU38518 T.p. 2L,R KU38521 T.c.a. 1L,R KU36617 T.p. 3L,R KU38522 T.c.a. 2L KU36618 T.p. 4L KU38523 P.p. 1L,R KU38526 T.p. 5R KU38524 P.p. 2L KU38527 T.c.p. 1L,R KU38515 P.p. 3L,R KU38528 T.c.p. 2L,R KU38516 P.p. 4L KU38529 T.c.p. 3L KU38517
The specimens were injected in the field either with formalin (10%) or embalming fluid, except for those of _T. c. att.w.a.teri_, which were frozen; the latter were later injected with embalming fluid. Injection in all the birds was by hypodermic syringe into all major muscle ma.s.ses, into the body cavities, and subcutaneously in the neck, wings, and feet.
In those specimens injected with embalming fluid, the body cavities were injected with formalin. The embalming fluid consisted of 70 per cent alcohol, glycerin (or propylene glycol), and formalin (full strength) in the approximate ratio of 78:20:2, respectively. This fluid gave good preservation; these specimens had the advantages of lacking almost entirely the irritating odor of formalin and of having pliable tissues.
The skin of those specimens originally injected with formalin was slit in several places and they were transferred to crocks containing embalming fluid (without the formalin). After a period of many weeks, with two changes of fluid, most of the formalin odor was eliminated and the muscles were sufficiently pliable to be easily dissected. All specimens were kept in containers filled with embalming fluid. No mold ever appeared, even though no phenol or other chemical was added.
To facilitate comparison, two or three specimens were frequently dissected simultaneously. The nerves and smaller muscles were dissected with the aid of a stereoscopic microscope mounted on a long movable arm.
In order satisfactorily to expose the lumbosacral plexus the posterior half of the sternum and pectoral muscles, as well as the abdominal viscera, were removed.
To insure more nearly accurate proportions, drawings of the pelvis and of some of the muscles were made with the aid of photographs of the several specimens listed above.
TERMINOLOGY
_Skeleton_