45 
humerus in the Apieryx, the true muscles of the back, which correspond to the second 
layer of the dorsal muscles in Man, become immediately visible on removing the dorsal 
integuments and fascix ; they consist of the sacro-lumbalis, longissimus dorsi, and spinalis 
dorsi. The first two muscles are blended together at their posterior origins, but soon 
assume the disposition characteristic of each as they advance forwards, 
The sacro-lumbalis (Pl. XI. XII. 1) is a strong and fleshy muscle, six lines in breadth, 
and three or four lines in thickness: it is, as usual, the most external or lateral of the 
muscles of the back, and extends from the anterior border of the ilium to the penulti- 
mate cervical vertebra. Origin. By short tendinous and carneous fibres from the outer 
half of the anterior margin of the ilium, and by a succession of long, strong, and flat- 
tened tendons (Pl. XII. 71-15) from the angles of the fifth and fourth ribs, and from 
the extremities of the transverse processes of the third, second, and first dorsal vertebre ; 
also by a shorter tendon (/ 6) from the transverse process of the last. cervical vertebra ; 
these latter origins represent the musculi accessorii ad sacro-lumbalem; to bring them 
into view, the external margin of the sacro-lumbalis must be raised, as in Pl. XII. fig. 2. 
These accessory tendons run obliquely forward, expanding as they proceed, and are lost 
in the under surface of the muscle. 
Insertion. By a fleshy fasciculus with very short tendinous fibres into the angle of the 
sixth rib, and by a series of corresponding fasciculi, which become progressively longer 
and more tendinous, into the angles of the fifth, fourth, third and second ribs (Pl. XI. /*), 
and into the lower transverse processes of the first dorsal and last two cervical vertebree : 
the last insertion is fleshy and strong ; the four anterior of these insertions are concealed 
by the upper and outer fleshy portions of the sacro-lumbalis, which divides into five elon- 
gated fleshy bundles (Pl. XI. /**), inserted successively into the upper transverse pro- 
cesses of the first three dorsal and last two cervical vertebre. These last insertions 
seem to represent the continuation of the sacro-lumbalis in Man, which is termed the 
cervicalis descendens or ascendens. 
Longissimus dorsi (Pl, X1. XI. m).—This muscle is blended posteriorly both with the 
sacro-lumbalis and the multifidus spine, and anteriorly with the outer portion of the 
spinalis dorsi. It extends as far forward as the thirteenth cervical vertebrae. Origin. 
From the inner or mesial half of the anterior margin of the ilium; from a strong apo- 
neurosis attached to the spines of the eighth, seventh and sixth dorsal vertebra ; and from 
the transverse processes of the sixth, fifth, fourth and third dorsal vertebrae. Ins. The 
carneous fibres continued from the second origin, or series of origins from the spinous 
processes, incline slightly outward as they pass forward, and are inserted into the poste- 
rior articular processes of the first three dorsal vertebrie, receiving accessory fibres from 
the spinalis dorsi. The fasciculi from the transverse processes incline inwards, and are 
also inserted into the posterior oblique processes of the vertebra anterior to them ; they 
receive fibres from the iliac origin, and soon begin to form a series of oblique carneous 
fasciculi, which become more distinct as they are situated more anteriorly ; they are at 
