55 



quadratics femoris. In the muscular system of the Ostrich and Lion 

 this antagonism between the muscles is very striking. It is found oc- 

 casionally in human subjects, and is described by Harrison under the 

 name of M. ilio-capsularis. While we had the Ostrich in the Dissecting 

 Eoom of Trinity College, a human subject was brought in, which had 

 the ilio-capsular muscle fully developed ; and my attention was called 

 to it by Dr. Bennett. I have occasionally found the ilio-capsular muscle 

 in dissecting Monkeys. 



In the Ostrich, the M. opponens has an origin on the anterior sur- 

 face of the ilium, between those of the Mm. sartorius, rectus, iliacus, 

 and glutceus medius, as shown at /, (Fig. 6) ; and is inserted in the anterior 

 riclge at the base of the great trochanter, with the M. glutceus minimus 

 (Fig. 7), with the fibres of which it is connected ; it weighs . . . 1 J oz. 



20. M. obturator. — In the Ostrich, as in most birds, the internal and 

 external obturator muscles are united, arising from both the inside and 

 outside of the bony circumference of the obturator foramen, and from 

 both sides of the obturator membrane ; their common tendon passes 

 through the ischiadic notch, n, (Fig. 6), which forms a pulley, changing 

 the direction of the force through 90°, and receives, on emerging from 

 the notch, the fibres of the little gemelli, placed at each side, anterior and 

 posterior, to guide the obturator tendon to its insertion (Fig. 7) on the 

 outer part of the top of the femur ; it weighs 1 71 oz. 



21, 22. — Mm. gemelli weigh ± oz. 



23. — M. coraco-clavicularis. — In the wing of the Ostrich there is a 



very remarkable muscle, which arises from the bony margin of the co- 

 raco-clavicular foramen; this foramen corresponds in the upper extremity 

 with the ischiado-pubic or obturator foramen of the lower extremity ; 

 and the muscle, passing under a strap ligament on the shoulder to be 

 inserted in the outer part of the great tuberosity of the humerus, cor- 

 responds with the obturator muscle of the leg. 



I consider this muscle to be the second pectoral of ordinary birds, 

 and to be the proper levator humeri. It is usually placed between the 

 first and third pectorals, on the sternum, and lifts the wing by means 

 of a pulley, which changes its direction through 135°. This contrivance 

 is necessary in birds of flight, in which it is of as much importance to 

 stow the weight aft, as it is in ships to place the foremast well forward ; 

 but, as the Ostrich is a running bird, the Divine Contriver has left 

 the second pectoral to lift the humerus by a direct pull, without ex- 

 pending any ingenuity on pulleys to change its direction, as is absolutely 

 necessary in birds of powerful flight such as the Falcon, in which the 

 pulley of the second pectoral is as remarkable a contrivance as the pul- 

 ley of the obturator muscle in the Ostrich. 



In fact, throughout the whole range of the muscular mechanism of 

 various animals, every pulley changing the direction of an original force 

 presents a problem to be solved ; and tells us of a contriving mind, which 

 has deviated, for some purpose discoverable by us, from the simple con- 

 trivance of muscular fibres pulling directly from their origin to their in- 

 sertion, 



