OF THE GREAT ANTERIOR VEINS. 
155 
costal system loses its integrity as development goes on; its middle and lower por- 
tions end in the azygos vein, either through an azygos minor, as in the usual case, or 
if that vessel be wanting, by independent intercostal branches*, or by both of these 
ways together-f-; or its lower branches may descend to the lumbar or renal veins'^. 
Its upper portion forms a left superior intercostal vein. 
The azygos vein, in these cases, formed towards its termination by the persistent 
trunk of the right cardinal vein, usually ends in the upper vena cava (the right 
canal of Cuvier), but its place of termination is said, though very rarely, to be 
moved on, as if by the fusion of the canal of Cuvier with the right auricle, so that it 
may end in the auricle itself:{:, or even approach the neighbourhood of the inferior 
cava, within the pericardium §(?), as occurs in some animals. 
The right superior intercostal vein, which is not formed by any part of the primi- 
tive venous trunks, frequently joins the arch of the vena azygos itself |1; but, with- 
out any other coexistent variation, its place of opening may be removed to the upper 
vena cava||, to the right innominate |], or subclavian veins^, or even to the vertebral 
vein**. 
The left superior intercostal vein, the trunk of which is generally formed by the 
metamorphosed portion of the primitive left jugular vein, immediately below the 
transverse branch in the neck, is, when present, almost constant in its mode of ter- 
mination, ending at the underside of the commencement of the left innominate 
vein-f'-f'. 
2. The right intercostal system retaining its integrity, hut unusually large. — There 
are various degrees of this condition, in which the azygos vein, besides receiving all 
the intercostal branches of its own side, including the superior intercostals, is joined 
by more than usual, or even by all the separate branches of the left side:|;:|:. In this 
latter case the ordinary left superior intercostal vein is very small or wanting, the left 
primitive jugular trunk having become obliterated quite up to the cross branch in 
the neck, as exemplified in the embryo, Plate III. fig. 4. 
A still more remarkable enlargement of the azygos vein has been rather often met 
with, in those cases in which, the inferior cava being deficient, the azygos conveys all 
the blood usually brought back by that vessel excepting what returns from the liver, 
which continues to pass by a short hepatic venous trunk directly into the heart. The 
* SoEMMERHiNG (De Corporis Human! Fabrica, vol. v. p. 373). 
t Breschet (Recherches sur le Systeme Veineux. Note, p. 8-10). 
t Cheselden (Philosopliical Transactions, 1713, vol. xxviii. p. 282). There is a doubt about this case, 
M'hich is again noticed in p. 161. Breschet {pp. cit. p. 9. note) in a child ten to twelve years of age. Soem- 
MERRINO {op. cit. p. 372). 
§ SoEMMERRINO {op. Cit. p. 376). 
II Breschet {op. cit. p. 12). 
^ HiLnEBRANDT (Lehrbuch der Anat. des Menschen, 1803, vol. iv. p. 281). 
** Haller (Element. Physiol, t. hi. p. 107 ; also t. i. lib. iv. pp. 308, 320). 
tt Hildebrandt (/, c.). Breschet {1. c.; also pi. 1. livr. i.). 
X 2 
