DEVELOPMENT OF THE THORACIC DUCT 151 



the oesophagus (8), trending sinistro-cephalad into the line of 

 the preazygos segment (35, in figs. 271 and 272). 



Reference to the dorsal view of the reconstruction of this em- 

 bryo (fig. 171) shows that the azygos segment of the thoracic 

 duct (36) has united with part of the caudal division of the preazy- 

 gos chain of lymphatics (35), cephalad of the interazygos anasto- 

 mosis, into a continuous lymphatic channel, although the con- 

 tinuity with the main preazygos segment has not yet been com- 

 pletely established. In other words this condition has been very 

 nearly, but not quite, attained. Some of the preazygos elements 

 (35} have already fused with the azygos segment, thus carrying 

 the latter cephalad beyond the interazygos anastomosis into the 

 territory of the preazygos portion of the thoracic duct. 



