42 



STRUCTURE AND CLASSIFICATION OF BIRDS 



Eiidyptes) has termed ' muscle diaphragmatique transverse.' 

 These muscles are, however, striated ; but the duck is not 

 the only bird with unstriated fibres in the oblique septum, 

 for these also occur in the toucan. 



In all birds, with the exception of certain passerines 

 possibly of the entire group of passerines the oblique septa 

 have the structure and relations that have been thus briefly 

 described. In passerines l they have undergone what appears 

 to be a modification. The oblique septa of each side, instead 



FIG. 28. VISCEKA OF BOOK DISPLAYED BY EEMOVAL OF ABDOMINAL WALLS. 



fit, gizzard ; L, liver; O.S, oblique septum. The liver is covered by a membrane 

 continuous with the oblique septa. 



of being attached independently to the sternum, become 

 fused with the falciform ligament in the middle line, and 

 form a horizontal sheet of membrane covering over the two 

 lobes of the liver. The original (?) attachments of the 

 oblique septa are not, however, in these birds entirely lost ; 

 a much fenestrated membrane sometimes, indeed, reduced 

 to a thread or two remains to remind the anatomist of the 



1 BEDDAKD, ' On the Oblique Septa in the Passerines, and in some other 

 Birds,' P. Z. S. 1890, p. 225. 



