. The development of the chick; an introduction to embryology. Birds -- Embryology. 440 THE DEVELOPMENT OF THE CHICK with the ventral posterior border of the iUum, and the pubis, except at its anterior and posterior ends, with the free border of the ischium. The spina iliaca, a pre-acetabular, bony process of the ihum, requires special mention in- asmuch as it has been inter- preted (by Marsh) as the true pubis of birds, and the element ordinarily named the pubis as homologous to the post-pubis of some rep- tiles. There is no evidence for this in the development. The spina iliaca develops as a
. The development of the chick; an introduction to embryology. Birds -- Embryology. 440 THE DEVELOPMENT OF THE CHICK with the ventral posterior border of the iUum, and the pubis, except at its anterior and posterior ends, with the free border of the ischium. The spina iliaca, a pre-acetabular, bony process of the ihum, requires special mention in- asmuch as it has been inter- preted (by Marsh) as the true pubis of birds, and the element ordinarily named the pubis as homologous to the post-pubis of some rep- tiles. There is no evidence for this in the development. The spina iliaca develops as a cartilaginous outgrowth of the ilium and ossifies from the latter, not from an inde- pendent center (Mehnert). The Leg-skeleton. The skeleton of the leg develops from the axial mesenchyme, which is at first continuous with the primordium of the pelvic girdle. In the process of chondrification it seg- ments into a larger number. Fig. 249. — Photograph of the skeleton of the leg of a chick embryo of 15 days' incubation. Prepared by the potash ^^ elements than found m method. (Preparation and photograph by Roy L. Moodie.) 1, Tibia. 2, Fibula. 3, Patella. 4, Femur. 5, Ihum. 6, Pleurocentra of sacral vertebrae. 7, Ischium. 8, Pubis. 9, Tarsal ossification. 10, Second, third; and fourth metatarsals. 11, First meta- tarsal. I, II, III, IV, First, second, third, and fourth digits the adult, some of w^hich are suppressed and others fuse together. The digits grow out from the palate-like ex- pansion of the primitive limb in the same fashion as in the wing. In general the separate elements arise in the proximo-distal order (Figs. 242 and 249). The femur requires no special description; ossification begins on the ninth day. The primordium of the fibula is from the first more slender than that of the tibia, though relatively far larger than the adult. Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration an
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Keywords: ., bookauthorlilliefrankrattray187, bookcentury1900, bookdecade1900
