1(J2 COUES ON THE OSTEOLOGY 



Phalanges. The four toes possess the number of segments which normally exist through- 

 out the vast majority of birds ; to wit, 2, 3, 4, 5, counting from the hallux to the outer toe. 

 Some special features of each may be noticed. 



Tbe hallux is of very moderate length, though comparatively longer than that of many 

 other families of Natatores. Its two segments, together with the claw and accessory meta- 

 tarsal, only measure one and a third inches. Its basal segment is long and very thin, and 

 compressed ; its ungual is scarcely more than an osseous nodule for the support of the claw. 

 Although this toe is not without its tendons, it appears to possess little motion, beyond 

 what may be imparted to it by its membranous connections with the next one. It is fur- 

 nished with a dependent lobe. 



The second toe is chiefly remarkable (besides its peculiar articulation with the meta- 

 tarsus already noticed) for the great length of its basal segment, which considerably ex- 

 ceeds that of the other two segments combined. 



All the phalanges of the middle toe are very stout and strong, much surpassing those of 

 either the inner or outer toes in this respect. It is intermediate in length between the 

 inner and outer toes. 



The outer toe is the longest of all. Its fourth segment, the penultimate one, presents 

 the peculiarity of being considerably longer than either the second or third. 



The mechanism by which the toes are separated from each other, or abducted, at the 

 same time that they are extended, forms an interesting feature in the feet of this and other 

 birds. The inetatarso-phalangeal articulation is a strict ginglymus, not admitting of lateral 

 motion, nor of rotation. But the median grooves of the heads of the metatarsal bone, 

 instead of running directly perpendicularly over the joint, are placed a little obliquely ; 

 i. e., that on the under head runs upwards and inwards ; that on the middle head slightly 

 outwards ; that on the outer head is much more oblique. The planes of the heads of the 

 metatarsus are also peculiarly twisted ; so that on their inferior aspects they all look to- 

 wards each other; but as they mount upwards, gradually turn outwards or away from 

 each other. Now the heads of the phalanges, when raised by the extensor tendous over the 

 joint, follow the direction of these oblique planes, being guided by their median ridge which 

 fits in the median sulcus in the metatarsal bone ; and so, by the time they are fully ex- 

 tended they also all look away from each other ; and the webs are by this means spread. 



Thus the toes when extended must also be carried from each other ; and they cannot be 

 approximated except when flexed. The intention of this peculiarity is evident. The more 

 forcibly the toes are pressed against the water the wider their webs are spread by the 

 resulting separation of the toes ; whereas if the toes could be approximated when in a 

 state of extension, it would require constant effort to preserve the expansion of the webs. 



Myology. 



Cuianeous muscles. The principal of these is the large muscle which lies immediately 

 beneath the skin of the neck and breast, so closely adherent to the skin as to be taken off 

 with the latter in ordinary skinning. It has quite an extensive origin on the breast, ex- 

 tending two or three inches on each side of the median line. The greater number of its 

 fibres converge to pass up on each side of the median line of the neck, as narrow slips ; 

 but a thin, yet compact layer of longitudinal fibres completely encircles the neck, reaching 

 quite to the occiput. 



