OSTEOLOGY OF BIRDS 



207 



Next, I have traced the development of the three metacarpal 

 bones, with their changes in form and in position. In connection 

 with them I find certain small cartilaginous elements, which soon lose 

 their independence, but leave traces in the full grown wing, viz (a) 

 a cartilage to the radial side of the first metacarpal, in the position 

 occupied by the spur of many birds, which calls to mind the pre- 

 pollex described by Bardeleben, Kehrer, and others, in amphibians, 

 reptiles, and even mammals ; l (b) a cartilage to the ulnar side of the 

 third digit, which probably is a remnant of the aborted fourth digit; 

 and (c) certain cartilages of more doubtful nature developed in con- 

 nection with the index finger, to its ulnar side, and afterwards fus- 

 ing with it. 2 



Lastly, I have made new observations on the small distal phalanges 

 in the fowl and other birds, and on the rudimentary nails and claws 

 of the second and third digits; and I have added a short revision of 

 the structure of the wing through the Ratitae. 



In the distal region of the carpus the fowl shows at no period 

 more than three separate elements. In this earliest (7-day) stage, 

 two only are recognizable [fig. 59, om and *.]. The larger of 

 these two lies in the middle of the carpus, and is in contrast both 

 with the intermedioradiale (radiale) and the centraloulnare (ulnare). 

 Its distal surface forms a concavity to receive the base of the second 

 digit. An evident crowding of cells in the embryonic cartilage 

 towards its radial side is the beginning of the formation of the first 

 carpale [fig. 59, 8], which will be seen distinctly in the next stage. 

 The third carpale [in the upper part of 2 in fig. 57 and 59, Parker 

 makes another ossification] is already distinct, lying in close relation 

 with the base of the third digit. 



In the next stage, on the 8th day of incubation, the various carpal 

 elements are all more solid and definite in form. The centraloulnare 

 is becoming bilobate, and has increased considerably in relative size ; 

 so as to be little less than the intermedioradiale. The three distal 

 carpalia are now all distinct, the middle one being still the largest, 

 the inner the least. 



In a chicken three quarters of a year old the wing is still far 

 from perfect . . . [while] in the full grown hen all the origi- 

 nal outlines of the distal carpals have become obliterated [p. 388]. 



In the chick of the 7th day the three metacarpals are completely 

 separate. That of the pollex is about one third the length of the 

 next in order, and is unossified ... In the chick of a 

 month old the first metacarpal is well ossified, and coalescing with 

 its larger neighbors. 



In very many birds (most Gallinacei, many Passerines, etc.) the 

 interosseous space between the metacarpals of the index and third 



1 Parker =eems to have overlooked the fact that as long ago. as 1883, the present 

 writer described and figured those additional osseous centers in the carpus of the 

 Gallinae, in his Osteology of the North American Tetraonidae, to which reference has 

 just been madr above. 



1 See the indicial process of the present writer's figure as above cited, figure 58 of 

 plate 7 of the Osteology of the North American Tetraonidae. These are the figures 

 quoted above in making the comparisons with Parker's work. 



