Talk:Book - Contributions to Embryology Carnegie Institution No.68

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Table 1. Showing correlation of size of embryos and development of the aortic-arch system.

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(Embryo Xo."

Length in mm.

Arches present.

Characteristic features.

[Time of establishment of first arch; estimated average length 1.3 mm.; 23d day of development*]

1878

1201

391

470

2053

1201b 836

1.3

2

4 3

3

4

I I 1 I I; II beginning

I. II

II, III

Slightly plexiform. Presomite stage

7 somites

Neuropores open; 14 to 16 somites

Anterior neuropore closed; 20 somites; transverse anastomoses between primitive aortae

Earlier mandibular aitery; paired longitudinal neural arteries; no ventral tract on cord

[Just before establishment of fourth arch; estimated average length 4 mm.; 31st day of development*]

826 1075 588 873 988 13S0

2S41

III, IV

Earlier mandibular and hyoid arteries

III, IV

Subclavian

111,1V

Earlier mandibular and hyoid arteries

III, IV

Ventral arterial tract on cord

III, IV

III, IV; pulmonary arches al

most complete

III, IV; one so-called fifth arch;

Early formation of basilar artery

pulmonary almost complete

[Just before completion of pulmonary arch; estimated average length 6 mm.; 36th day of development*]

810

1354 617

792 1121

721 163

8 11

III, IV, and pulmonary arches

III, IV, and pulmonaiy arches III, IV, two so-called fifth arches,

and pulmonary arches III, IV, and pulmonary arches III, IV. and pulmonary arches

III, IV, and pulmonary arches III, IV, and pulmonary arches

Late stage in formation of basilar artery, distinct. Unpaired aorta complete

Splitting of aortic sac

Subclavian artery surrounded by brachial plexus. Splitting of sac

well marked. Islands at end of basilar arteryPulmonary and IV arches widely separated belowRight pulmonary artery small; basilar rounded; IV and pulmonary still farther apart Cervical segmental arteries becoming interrupted Anastomoses of cervical segmental arteries to form the vertebral artery are nearly complete

[Time of interruption of pulmonary arch and of branchial period; estimated average length 12 mm.

45th day of development*]

1771 544

940

1909

492

74

13 10 14

15 16 16

III, IV, left pulmonary and remnant of right pulmonary arch

Vertebral artery complete; identity of arches disappearing; beginning of period of rapid descent of heart and arteries

Definitive aortic arch just taking form. Right dorsal aorta between III and IV interrupted. Remnants still distinguishable. Main pulmonary channel from heart to aorta nearly straight

Common carotid elongated

Right dorsal aorta distal to IV patent but slender

End of period of descent. Definitive aortic arch has curve of large radius. Short segment of right dorsal aorta distal to subclavian drawn out in slender thread

[End of period of rapid descent of heart and arteries; estimated average length 18 mm.; 50th day of development*]

1390

18

460

20

2937

24

S86

43

Definitive aortic arch sharply bent

Summit of definitive aortic arch at superior thoracic aperture Sternal bands in contact through most of their length Origin of right and left pulmonaiy" branches in contact through most of their length

Estimates based on Mall's (1912) curve of length and age.