31 
tissue divides the internal oblique from the transverse abdominal, 
except at its origin from the pubis, and for half an inch anterior to 
that part. 
The transversalis then proceeds to derive carneous fibres from the 
inner surface of the vertebral ribs near their lower third ; they pass 
obliquely upwards and forwards, and terminate bya regular, slightly 
concave line midway between their origins and the extremities of 
the ribs; a strong aponeurosis passes thence to the linea alba, but 
becomes thin at the pubic region, where a mass of fat is interposed 
between it and the peritoneum. 
Diaphragm.—This muscle presents more of its normal mammalian 
character in this than in any other known bird. It is perforated by 
vessels only, in consequence of the non-development of the abdominal 
air-cells. The origin corresponding to that of the lesser muscle in 
Mammalia is by two strong and distinct, short tendinous pillars, from 
the sides of the body of the last costal vertebra; they are united by 
a strong tendon or fascia, forming the anterior boundary of the aortic 
passage. ‘The tendinous pillars may be traced forward for some way 
in the central aponeurosis, expanding without crossing; they are 
then lost in that aponeurosis, which is perforated by the gastric arte- 
ries and veins; divides anteriorly to give passage to the gullet and 
the apex of the heart; the aponeurosis expands over the anterior 
part of the thoracic air-cells, and becomes, at its lateral circumfe- 
rence, the point of attachment of muscular fibres arising from the 
inner surface of the anterior ribs, and forming apparently a continu- 
ation of the transversalis abdominis. 
Intercostales externi.—Origin. From the posterior edge and ex- 
tremity of the costal processes or appendages. Ins. They run down 
to be inserted severally into the rib posterior to that to which the 
process affording them origin is attached. These processes are sup- 
ported by strong triangular aponeuroses continued from their anterior 
and upper margins, severally, to the rib anterior to them. 
A strong muscle arises from the anterior or costal angle of the 
scapula, and passes backwards to be inserted into the extremity of 
the third vertebral rib and its corresponding sternal portion. This 
muscle is a direct inspirator. 
Muscuzs or tHE ANTERIOR EXTREMITY. 
Serratus magnus anticus.—This muscle consists of three portions ; 
the first and anterior portion arises by a short, strong aponeurosis 
from the last cervical rib, and is inserted into the lower edge of the 
anterior two-thirds of the scapula: the second middle portion arises 
from the lower end of the second vertebral rib, near the attachment 
of the costal process, and from the anterior margin of the same rib, 
and is inserted into the lower edge of the posterior two-thirds of the 
scapula: the third, posterior and smallest portion rises from the costal 
process of the third rib, and ascends to be inserted into the posterior 
extremity of the scapula. 
This muscle is a direct inspirator: by drawing down the scapula 
it depresses the sternum through the medium of the strong coracoi- 
B 
