206 FREDERICK TILNEY 



the azygos-Cuvierian junction to a level slightly above the inter- 

 renal anastomosis. It is notable for its unusual size as well 

 as for the striking resemblance it bears to the reptilian type of 

 axial lymph channel (fig. 9, 28). On approaching its cephalic 

 extremity the channel breaks up into a rich plexus (fig. 8, 50). 

 The same is true of its caudal extremity. The vessel on the 

 left side is the larger. It is situated ventro-mesial to the azygos 

 vein and dorso-lateral of the aorta. The right channel holds 

 the same relative position. After proceeding a short distance 

 caudad these two parallel channels rapidly expand and become 

 confluent across the median line behind the aorta. The azygos 

 segment interposes itself between that vessel and the two azygos 

 veins, which latter are connected with each other by anastomos- 

 ing vessels passing behind the aorta. The relations of the azygos 

 segment to the other large channels are illustrated in cross section 

 in fig. 9. 



2. The post-azygos segment (fig. 7, 29). This portion of the 

 systemic lymphatic channel pertains to the abdominal region 

 where it appears as an irregular vessel, at times double and 

 again fused, behind the aorta. It continues downward in this 

 condition to the iliac bifurcation where it becomes a considerably 

 dilated, single vessel again bifurcating at its caudal extremity. 

 At the point of this bifurcation it alters its relations in such a 

 manner as to lie lateral to the iliac vein, taking up the ultimate 

 position of the ilio-lumbar lymphatic trunks. At its cephalic 

 extremity it ends in a plexus which has already established sev- 

 eral connections with the plexus at the caudal extremity of the 

 azygos segment. 



3. The pre-azygos segment (fig. 7, 30 and 31). In this portion 

 of the systemic lymphatic channel the process of expansion is 

 apparently less active than elsewhere. Two general lines of 

 development may be traced, one on the right in relation to rem- 

 nant of the right pre-cardinal vein and aorta, the other on the 

 left in relation to the large brachio-cephalic arterial trunk. Each 

 line presents a cephalic and caudal element. On the right side the 

 caudal element communicates with the plexus at the cephalic end 

 of the azygos segment (fig. 8, 50), and from here extends cephalad 



