428 C. J. Sundevall on the Wings of Birds. 
is only an inconsiderable shallow depression in the place of 
this latter, and that between the two wing-bones is broad 
but not deep. In Ficus the two pits are formed as in the 
Song-birds, but somewhat shorter. Hirundo has them both 
longest and deepest of all birds known to me. 
As this difference in the exterior is manifestly founded 
upon a different arrangement of the parts situated under the 
skin, it seemed natural to make a new investigation of the 
muscles; and although this has not been successful in fur¬ 
nishing the grounds of an explanation of the differences in 
the wing-feathers of the Song-birds and the other orders, what 
has been ascertained may nevertheless be briefly recorded. 
The muscles of the wing have already been described by 
several authors, but best, and with a comparison of all orders, 
by Schopss in Meckel’s f Archiv/ 1829. This remarkable 
memoir ascribes to the whole wing forty-eight muscles, of 
which I propose to mention only a small part, namely, the 
muscles of the cubitus, and, supplementarily, those of the 
humerus. I pass over the muscles of the hand, as also those 
of the shoulder ; and with regard to the latter I will merely 
remind the reader of the corrections recently made by Retzius 
(Skand. Naturf. Sallsk. Forhandl. 1842) upon the older 
descriptions of them. 
Under the skin the whole of the forearm is, as usual, 
clothed with a thin aponeurosis [fascia cuhiti ), which gives 
off sheaths between the muscles, sinew-sheaths, &c. In 
birds it also forms a peculiar independent band ( fascia 
ulnaris), which commences right upon the convexity of the 
humeri condylus internus, and finishes with one end upon the os 
pisiforme , and with the other in the ligamentum carpi. This 
band therefore lies along the ulna, but separated from it by 
a considerable space, which is occupied by the flexor 
muscles. Only in the lowest Water-birds ( Pygopodes ) it 
lies close upon the ulna, united to the bone like a direct 
continuation of the periosteum. It always passes straight 
forward, strongly strained between its points of attachment. 
This band plays a principal part in our exposition, and I 
