"coracoid complex."

The first artery (11) of this complex arises from any one of several places: from the lateral face of the coracoid artery at its base; independently from the subclavian immediately lateral to the origin of the coracoid artery; and from the thoracic artery near its origin. This vessel travels laterad, parallel to the subclavian, and penetrates M. coracobrachialis posterior at the same point that the pectoral artery passes dorsal to that muscle.

Another vessel (common stem of 4 and 5) of the coracoid complex in most specimens arises from the anterior face of the coracoid artery and branches into several vessels, some of which (5) supply M. subcoracoideus, and some of which (4) feed M. coracobrachialis posterior. The vessel occasionally shares a common stem with the main vessel (11) to M. coracobrachialis posterior, and in some specimens arises independently from the subclavian, immediately anterior to the origin of the coracoid artery. The branch (4) to M. coracobrachialis posterior was also seen to arise independently from any of the above-mentioned positions.

Two remaining vessels (6 and 8) are often found as branches from the coracoid artery. They were small and often were collapsed in the individuals I dissected, but were most clearly seen in Iridoprocne bicolor. The vessels occasionally had a common base, and in some specimens only one vessel was found. The first artery (6) passes mediad into M. sternocoracoideus, or continues across that muscle onto the inner face of the sternum. The second vessel (8) also supplies M. sternocoracoideus or the inner surface of the sternum, and often a large branch continues across the dorsal surface of the coracoid to M. coracobrachialis posterior. Fig. 3 shows a composite of these vessels; not all branches were seen in any one specimen. In the specimen of I. bicolor a foramen existed on the lateral edge of the coracoid where the branch (of 8) to M. coracobrachialis posterior passed. An examination of skeletons of five to 10 individuals each of the five species for which dissections were made, and of Petrochelidon pyrrhonota (Cliff Swallow) and Tachycineta thalassina (Violet-green Swallow), in the University of Kansas collection, showed that most coracoids of these seven species of swallows had a small notch (as shown in Fig. 4) or a complete foramen there.

The thoracic artery (3) arises from the subclavian opposite the base of the coracoid artery, or from the base of the coracoid artery. Of the five specimens of P. subis dissected, one individual had the former arrangement on both sides, and one had the latter on both sides, whereas in the remaining three the thoracic artery arose from the coracoid artery on one side and from the subclavian on the other side. The distance between these two possible sites of origin is slight.

The thoracic artery usually passes ventral to M. costi-sternalis anterior. Occasionally a small artery (13) could be traced from the main trunk of the thoracic artery to that muscle. The main thoracic artery bifurcates near the insertion of M. costi-sternalis, the branches traveling posteriad on both sides of the muscle. On one side of one specimen this artery bifurcated immediately after leaving the subclavian, the dorsal trunk passing dorsal to M. costi-sternalis anterior, and the ventral trunk ventral to the muscle. On the other side of the same individual the artery passed dorsal to M. costi-sternalis anterior, bifurcating at the normal point.

From the ventral trunk of the thoracic artery a variable number of small vessels arises to supply the costosternal articulations. The main ventral trunk bifurcates into two branches, one of which passes onto the inner face of the sternum, and one of which supplies the posterior two intercostal spaces.

The dorsal thoracic trunk supplies M. costi-sternalis, several dorsal intercostal areas, and the costopulmonary muscles. Minor variations in all of the smaller branches of the thoracic artery were common.

MYOLOGY AND ANGIOLOGY: COLUMBIDAE

Figs. 5, 6, and 7 illustrate the following muscles and arteries described for Scardafella inca.

Myology

M. pectoralis thoracica, Fig. 5. The origin is from approximately the ventral third of the keel, the lateral and anterior portion of the clavicle and the adjacent sterno-coraco-clavicular membrane, and from the lateral portion of the sternum and the fascia overlying the thoracic ribs. This massive muscle covers the entire ventral surface of the thorax, converges, and inserts on the pectoral surface on the ventral side of the humerus.

M. supracoracoideus, Fig. 5. The origin is from the dorsal two-thirds of the keel and medial half of the sternum (where the origin is bordered ventrally, posteriorly, and laterally by the origin of M. pectoralis thoracica) and from the sterno-coraco-clavicular membrane adjacent to the coracoid. This large pinnate muscle converges, passes through the foramen triosseum, and inserts by means of a strong tendon on the dorsal surface of the humerus on the deltoid ridge.

M. coracobrachialis posterior, Fig. 5. The origin is from a prominent lateral wing on the posterolateral portion of the coracoid, and from the lateral surface of the proximal two-thirds of the coracoid. The insertion is by means of a tendon on the internal tuberosity of the humerus. Of the muscles described here, this one differs most strikingly from the homologous muscle in P. subis. The difference can be seen by comparing Figs. 1 and 5.

M. sternocoracoideus, Figs. 5, 6, and 7. The origin is from the external, and to a slight extent from the internal, surface of the costal process. The insertion is on a posterolateral triangular area on the dorsal surface of the coracoid.

M. costi-sternalis, Figs. 5 and 6. The origin is from the anterior edge of the sternal portion of the first three thoracic ribs. The muscle converges and inserts on the apex of the costal process.

M. subcoracoideus (ventral head), Fig. 6. The origin is from the manubrium and from approximately the posterior half of the coracoid and on the medial and dorsal surface of that bone, and the medial side of the sterno-coraco-clavicular membrane adjacent to the coracoid. The ventral head passes anterodorsally to join with the dorsal head (not here described), and the combined muscle inserts by a tendon on the internal tuberosity of the humerus.

Mm. intercostales externus, Fig. 5. These muscles extend posteroventrally between successive thoracic ribs and between the last cervical and first thoracic ribs.

Mm. intercostales internus, Fig. 7. These muscles extend anteroventrally between the last three thoracic ribs.

Costopulmonary muscles, Fig. 7. This series of muscle slips from the thoracic ribs attaches to the aponeurosis covering the lungs.

Angiology

Figs. 5, 6, and 7 show all arteries discussed for this family. The numbers following names or descriptions of arteries in the text refer to numbered arteries in one of these figures. Insofar as possible, the numbers used for these arteries are the same numbers used for the homologous vessels in swallows.

The right and left innominate arteries arise from the aortic trunk and give rise to the common carotid (14) and subclavian (1) arteries. The latter continues across the thoracic cavity, giving rise to the coracoid (2) and axillary (10) arteries, and becoming the pectoral trunk. That trunk swings posteriorly and leaves the thoracic cavity near the apex