absence of the infekior cava below the diaphragm. 17 



Group Va. 



The same transposed in situs inversus. 



Hcrholdt. — Iliac veins united to form trunk on right of aorta, 

 which in the thorax passed to the left and ended in the trans- 

 posed superior cava. 



GrROUP VI. 



Persistence of the lower part of the left and the upper part 

 of the right posterior cardinal, with high union- of the 

 iliac veins. 



Gurlt. — Each common iliac vein received its own renal, after 

 which they joined on the left of the aorta, later in the thorax 

 the vein passed to the right end in the superior cava. 



Kollmann. — The iliacs united at the junction of the renals in 

 a great plexus of large veins. The resulting trunk, at first on 

 the left, ran like the preceding. (I have not found any 

 instances of the reversal of this condition in situs inversus.) 



There is quite a family likeness in the minor details of this 

 collection of anomalies, putting aside Hyrtl's and Martin's. 

 The latter, however, should be compared with that of Dorsch, 

 inasmuch as both may possibly have the left duct of Cuvier 

 still persisting. With the exception of these cases, the upper 

 part of the right posterior cardinal which forms the azygos (or 

 the left in inversion) is normal. This is not to be wondered at, 

 as there is no reason why an arrest of development of a tribu- 

 tary of the hepatic veins should disturb the upper part of the 

 posterior cardinals. What is more remarkable is the compara- 

 tive frequency of the persistence of the lower part of the left 

 cardinal, and the branch crossing to the right. The explana- 

 tion is perhaps to be found in the tendency to break down of 

 the middle part of the cardinal veins occurring on the right 

 below and on the left above the oblique anastomosis between 

 them which normally constitutes ihe azygos minor. It is un- 

 likely, however, that the interruption on the left occurs so high. 

 A more probable explanation is the tendency in the organism 

 to retain this feature of the normal arrangement. I have come 

 across the account of one case which does not quite enter this 



VOL. XXXV. (N.S. VOL. XV.) — OCT. 1900. B 



