434 Harriet Lehmann, Embryonic history of the aortic arches in mammals. 



Fig. 14, Reconstruction of the aortic arches in a pig embryo of the 

 twentieth day. 49 : 1. Surface view of the same is shown in Fig. 13. 

 /, II the first and second arches in process of degeneration, x and y 

 apparent ventral remnants of the first arch- VI the sixth arch in process 

 of formation. 



Plate 24. 



Fig. 16. Reconstruction of the aortic arches in a pig embryo of the 

 twentieth day (No. 2). 40 : 1. Surface view of the same is shown in 

 Fig. 15. /, // degenerating first and second arches. 



Fig. 18. Reconstruction of the aortic arches in a pig embryo of the 

 twentieth day (No. 3). 39 : 1. Surface view of the same is shown in 

 Fig. 17. /, // dorsal remnants of the first and second arches, x ventral 

 remnant of the second arch. 



Fig. 20. Reconstruction of the aortic arches in a pig embryo of 

 the twentieth day (No. 4). 29 : 1. Surface view of the same is shown 

 in Fig. 19. / and II dorsal remnants of the first and second arches. 

 b small branch from the ventral end of the third arch ; a sinus in slight 

 connection. T" a ventral bud of the forming fifth arch. 



Fig. 22. Reconstruction of the aortic arches in a pig embryo of 

 the twentieth day (No. 5). 25 : 1. Surface view of the same is shown 

 in Fig. 21. /, // dorsal remnants of the first and second arches, b small 

 branch from the ventral end of the third arch. V ventral bud of the 

 forming fifth arch. 



Plate 25. 



Fig. 24. Reconstruction of the aortic arches in a pig embryo of 

 twenty-one days development. 20 : 1. Surface view of the same is shown 

 in Fig. 23. /, // dorsal remnants of the first and second arches, e. c 

 external carotid, c place of union of the vessels of the two sides. V, a 

 complete fifth aortic arch. 



Fig. 26. Reconstruction of the aortic arches in a pig embi-yo of 

 the twenty-second (?) day. 25 : 1. Surface view of the same is shown in 

 Fig. 25. c union of the vessels of the two sides. / small branches from 

 the external carotid, a place of union of the pulmonary arches. F, a 

 degenerating fifth arch. 



Fig. 28. Reconstruction of the aortic arches in a pig embryo of 

 the twenty-third (?) day. 18,2 : 1. Surface view of the same is shown 

 in Fig. 27. ,c the place of union of the two fourth arches. ;; pulmonic 

 trunk. 



