34 



WILLIAM A. LOCY AND OLOF LARSELL 



R.D.B. 



Tra 



R.D.B. - 



Pul.At. 



LD.B. 



R.D.B 



68 



Fig. 65 The arterial trunk.s on the nineteenth day of development. The 

 sixth aortic arches are con.structed behind the ])uhnonarv arteries into the ducti 

 Botalli. Drawn by G. H. A. Rech. 



Fig. 66 Condition of the pulmonary artery and of the ductus Botalli of the 

 newly hatched fowl. Drawn I)y G. H. A. Rech. 



Fig. 67 The atrophied ductus Botalli and the enlarged pulmonary artery on 

 each side, on the third day after liatching. Drawn by G. H. A. Rech. 



Fig. 68 The heart and the arterial trunks on the third day after hatching. 

 The ductus Botalli of each side is reduced to a slender cord and the pulmonary 

 arteries have attained the diameter of the sixth arch of which they are contin- 

 uations. Drawn by G. H. A. Rech. 



