84 AVES. 



the dorsal and lumbar region are, on the contrary, less distinct and 

 much more feebly developed. 



The muscles which correspond to the rectus capitis anticus major 

 ct minor latcralis, tracJiclo-mastoidous, complexus, biventcr cervicis 

 (the last, however, being wanting in the Herons), are very large and 

 powerful. 



From the tail serving in Birds, as a very moveable rudder to 

 steer their course through the air, the muscles which are found up- 

 on the caudal portion of the vertebral column are very strong and 

 distinct, and arise from the pelvic and lumbo-sacral bones, which 

 afford them a fixed point of attachment. By these muscles the 

 tail itself is elevated, depressed, and lateralized, and by means of 

 other very powerful fasciculi, which are attached to the proximal 

 ends of the remigial feathers, these also can be expanded or approxi- 

 mated. 



A great portion of those muscles which lie immediately upon the 

 trunk, namely, the costal and abdominal muscles (m. m. intcrcostales 

 externi et intcrni, serratus anticus major, latissvnas dorsi, m. ret- 

 tus externits, internus transversus abdominis), are but slightly de- 

 veloped, and of a very flattened form. The abdominal muscles, 

 which, though broad and weak are however constantly present, form 

 only a thin covering over the viscera, which are protected for the 

 greatest extent by the large and expanded sternum ; they have no 

 transverse tendinous intersections, but are united in the middle by a 

 broad white line (linea alba}. The rectus muscle of the abdomen 

 frequently does not pass to the pubis, but blends with its fellow of the 

 opposite side in the sphincter of the anus. 



The diaphragm, which is most developed in the Ostrich, is repre- 

 sented by small muscular fasciculi, which usually arise by digitations 

 from the four middle sternal ribs, and are attached to a thin tendinous 

 aporieurosis, which is spread over the inner and inferior surface of 

 the lungs. 



The pectoral muscles are enormously developed, more especially 

 the pectoralis major, the fleshy mass of which in certain instances 

 weighs as much as all the rest of the muscles put together. It 

 arises from the keel and posterior and external part of the lower 

 surface of the sternum, and from the furcular bones, and is inserted 

 into the humerus, and serves to depress forcibly the latter bone, so 

 as to produce the downward stroke of the wing in flight. Beneath 

 it there lies a second muscle or pectoralis minor, and beneath that 

 again a third. In the Ostrich the origin of the pectoralis major is* 



