222 Zoological Society. 



sections, and is finally inserted into the xiphoid and lateral processes 

 of the sternum and the intervening fascia. 



Transversalis abdominis. — A layer of loose, dark- coloured cellular 

 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 cameous fibres from the 

 inner surface of the vertebral ribs near their lower third ; they pass 

 obliquely upwards and forwards, and terminate by a 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. 



Muscles of 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. 



