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=Four Cases of Anomalous Inferior Vena Cava with an explanation of their Developmental Origin=

By E. V. Maxwell and G. S. Erwin,

Students in the Department of Anatomy, University of Otago, Dunedin, New Zealand


==Introduction==

Dorie the past few years four cases of anomalous inferior vena cava have been observed in the dissecting room of this department. At the suggestion of Prof. Gowland, we have assembled the particulars of these cases and here present them with a brief discussion of their probable developmental origin. The developmental interpretation is in each case based on the recent work of McClure and Butler; to illustrate our remarks we have prepared, from the figures given by these writers, the composite diagram which constitutes our fig. 1.

* {{Ref-McClure1925}}

To Dr J. Mark, Dr M. A. Radcliffe-Taylor, and Mr C. J. C. Britton we are indebted for particulars in connection with certain of the cases.

A bibliography of the anomalies of the inferior vena cava is appended.

==I. Case of Left Inferior Vena Cava==

(Fig. 2) 

===Description of case===

The subject was an adult male (Italian).

The inferior vena cava in this case may be divided into three parts accord- ing to its relation to the aorta.

(a) The first part, corresponding to the postrenal portion of the vessel, lay on the left side of the aorta, which it displaced to the right of its normal position. The vena cava was formed at the level of the fourth lumbar vertebra, below and a little to the left of the bifurcation of the aorta, by the union of the two common iliac veins, and ascended on the left side of the aorta to the level of the first lumbar vertebra, where it received the left renal vein. The left sper- matic vein, instead of entering the left renal vein, joined the inferior vena cava about 14 inches below the entry of the left renal vein.

(b) The second part of the vena cava lay ventral to the aorta, passing obliquely upwards and to the right. It received on its left aspect the left supra- renal vein.

(c) The third part of the vessel lay to the right of the aorta, and received the following tributaries, in order from below up:

(1) A large vessel which, for reasons to be explained later, we may term the persistent right supracardinal. This vessel itself was joined, about 4 inch below its union with the inferior vena cava, by the right spermatic vein, and below this again by a large lumbar vein which appeared to be the chief tributary of the persistent right supracardinal, causing a sudden increase in its size.



Fig. 1. Composite diagram to show the development of the human inferior vena cava. Prepared from a series of figures given by McClure and Butler. A, B, and C = Intersupracardinal anastomoses.

(2) The right renal vein, which entered the inferior vena cava just above the persistent right supracardinal and almost together with it, though the two could hardly be said to form a common trunk.

(8) The right suprarenal vein, which entered the inferior vena cava about 3 inch above the entry of the right renal vein. Above the entry of the right suprarenal vein the course of the inferior vena cava was normal. 

===Developmental Interpretation===

According to McClure and Butler, the postrenal part of the inferior vena cava consists of the right lumbar supracardinal vein together with part of the supracardino-subcardinal anastomosis (fig. 1). We believe that in this case the postrenal vena cava is a reversal of the normal and therefore consists of (1) the left lumbar supracardinal, into which drain the two common iliac veins, and (2) the left supracardino-subcardinal anastomosis, joined by the left renal vein. As already stated, the left spermatic vein joined the inferior vena cava, not the left renal vein; this is in agreement with the abnormal development and is what is usually found in cases of left inferior vena cava.

The prerenal part of the vena cava consists of (1) the intersubcardinal anastomosis, (2) the pars subcardinalis (prerenal), and (8) the pars hepatica.

The large vessel which joins the inferior vena cava on the right we have called the persistent right supracardinal. According to McClure and Butler, the right lumbar supracardinal has the following characters: (1) above, it joins the inferior vena cava just at the entry of the right renal vein; (2) it re- ceives the right spermatic vein; and (3) below, it joins the right common iliac vein. The vessel which we have termed the persistent right supracardinal (1) opened above into the inferior vena cava just below the entry of the right renal vein, (2) received the right spermatic vein, and (3) was probably con- nected with the right common iliac vein; certainly 4 small vein (fig. 2) was observed joining the right common iliac, and, although, owing to the small size of the veins in question at this level, the connection between this and the right supracardinal was not established by dissection, their direction and calibre seemed to indicate their continuity. We therefore believe that the vessel which we have termed the persistent right supracardinal may justifiably be regarded as a secondary right inferior vena cava.

==II. Case of Double Inferior Vena Cava==

(Fig. 3)

Description of case

The subject was an adult female.

The inferior vena cava was symmetrically double in its postrenal portion, the two vessels running up one on either side of the aorta and uniting ventral to it at the level of the entry of the left renal vein. The unusual feature of this case was the relatively oblique course of the two caval trunks. (Cases with such an inclination of the vessels have frequently but erroneously been ascribed to abnormally high union of the two common iliac veins.) Just above the union of the external and internal iliac veins on each side, the two symmetrical trunks were connected by a small transverse trunk which lay dorsal to the common iliac arteries and ventral to the body of the fifth lumbar vertebra.

The lumbar veins were more or less normal, and in any case did not affect the anomaly. The transverse lumbar veins from both sides joined the right caval trunk in the usual way. Each ilio-lumbar vein joined the common iliac vein of its own side. The continuity of the ascending lumbar veins with the azygos veins was not demonstrated and is not shown in the figure.





Fig. 2. The principal veins in Case 1 (Case of left inferior vena cava).

The right ovarian vein joined the right caval trunk at the normal level, while the left ovarian vein joined the left caval trunk at a corresponding level. A small vein, apparently lumbar, joined the right caval trunk a short distance below the entry of the right renal vein, and a similar one joined the left renal vein itself.

===Developmental Interpretation===

McClure and Butler have shown that, in the early stages of development, the human inferior vena cava is symmetrical postrenally, consisting on each side of the following parts from below up: (1) the lumbar supracardinal, connected below with the corresponding common iliac vein, which is united with its fellow by the iliac anastomosis, and (2) the supracardino-subcardinal  anastomosis. Above the level of the kidney the vessel is single, and consists of (1) the pars subcardinalis (prerenal) and (2) the pars hepatica. 











Fig. 3. The principal veins in Case 2 (Case of double inferior vena cava).




The anomaly described above is by no means an uncommon one, and is due to persistence of both lumbar supracardinals instead of, as is usual, the right one only. Thus the inferior vena cava is double postrenally, and the right trunk consists of the same embryological parts as the normal postrenal inferior vena cava. The left trunk is the counterpart of the right and consists of corre- sponding parts, with the addition of the intersubcardinal anastomosis, which normally forms part of the left renal vein. The left renal vein is consequently shorter than usual, being only approximately as long as the right renal vein.

The transverse trunk mentioned in the description above represents a per- sistence of the embryonic condition in which there is a great iliac anastomosis in the same position. For this reason the position of junction of the transverse vessel with the caval trunks marks on each side the point of merging of the common iliac vein with the supracardinal vein. The right caval trunk, as we have already seen, represents the normal postrenal inferior vena cava, and the transverse trunk normally becomes incorporated in the left common iliac vein.

==III. Case of Anomalous Vena Azygos Major and Inferior Vena Cava==

(Fig. 4)

Description of case

The subject was an adult male.

The chief characteristic of this case was the continuity of the vena azygos major with the inferior vena cava by two separate channels, which we may term the right and left communicating trunks.

The right communicating trunk arose from the right aspect of the inferior vena cava about 4 inch below the entry of the right renal vein; it then ran up- wards and to the right, passing dorsal to the right renal vessels and dorsal to the medial part of the right suprarenal gland. It then inclined a little to the left, and, at the level of the dorsal attachment of the diaphragm, it united with the left trunk to form the vena azygos major.

The left communicating trunk arose from the left aspect of the inferior vena cava about 1 inch below the level of the entry of the renal veins (i.e., about 4 inch below the origin of the right trunk), and ran upwards and to the left to lie dorsal to the aorta and associated structures. It then arched to the right, dorsal to the main inferior vena cava, and finally, just after passing be- tween the crura of the diaphragm, united with the right trunk to form the vena azygos major as above described.

The vena azygos major was much larger than usual, being about 3 inch in diameter. This enlarged vessel followed its normal course, receiving the usual segmental tributaries, and arching over the root of the lung to join the superior vena cava in the normal manner.

The prerenal part of the inferior vena cava had connected with it a small collateral vessel, which received the right suprarenal vein. This collateral vessel pursued an arched course, being connected with the inferior vena cava (a) below, about } inch above the entry of the right renal vein, and (b) above, just below the caval opening of the diaphragm. There were also present on the right side two small accessory renal veins.



Fig. 4. The principal veins in Case 3 (Case of anomalous vena azygos major and inferior vena cava).

===Developmental Interpretation===

In the early stages of the development of the inferior vena cava (fig. 1), the supracardinals continue from the lumbar region into the thorax, and unite above with the postcardinals on each side. There are also present several inter- supracardinal anastomoses (4, B and C in fig. 1). Four Cases of Anomalous Inferior Vena Cava 191

In the present case, apart from the presence of the two communicating trunks, the postrenal inferior vena cava is normal and is formed in the manner already described. The right communicating trunk may be explained as being a persistence of the union between the thoracic and lumbar supracardinals on the right side. The left trunk is best explained as a persistence of (1) an inter- supracardinal vein (C in fig. 1) in the lumbar region, below the renal vessels, (2) an intersupracardinal vein (B in fig. 1) just below the diaphragm, and (8) the part of the left supracardinal vein between these two intersupracardinals. This explanation accounts for the position of the left trunk dorsal to the aorta in part of its course, as well as its junction with the vena azygos major.

The small arched vein communicating with the prerenal part of the inferior vena cava is probably due to the enlargement of one of the capillaries from which the pars hepatica is formed. It may, however, be due to the enlargement of a capillary between the right suprarenal vein and the pars hepatica.

==IV. Case Of Obstructed Hepatic Portion Of Inferior Vena Cava==

(Fig. 5)

===Description of case===

The subject was an adult female.

The part of the inferior vena cava between the entry of the right renal vein and the entry of the hepatic veins was represented by a fibrous cord 7 cm. long and 7 mm. in diameter. The cord was flattened, apparently by pressure of the viscera lying on it, but microscopic examination revealed its venous structure. The hepatic veins and the part of the inferior vena cava between them and the right auricle were normal, as was also the postrenal portion of the inferior vena cava.

From the upper extremity of the postrenal inferior vena cava the blood passed by two large channels, which we may term right and left.

(a) The Right Channel. This arose from the dorsal aspect of the inferior vena cava at the level of the entry of the right renal vein. It ascended verti- cally and passed through the aortic orifice of the diaphragm to continue as the vena azygos major, which opened into the superior vena cava in the usual manner. At the level of the first lumbar, eleventh, tenth, and ninth thoracic vertebrae, the vena azygos major was connected by four transverse anasto- moses with the vena azygos minor; it received the right intercostal veins, the spinal branches of the tenth and eleventh being enlarged.

(b) The Left Channel. Arising from the inferior vena cava opposite the entry of the right renal vein, this channel first coursed transversely to the left, passing ventral to the aorta; it then turned downwards, but almost immediately doubled back on itself in order to proceed vertically upwards, lying on the bodies of the vertebrae to the left of the aorta. It pierced the diaphragm at the level of the second lumbar vertebra, and thereafter continued as the vena azygos minor, which in its lower part was slightly tortuous. The vena azygos minor in its turn was continuous with the left superior intercostal vein, which opened above into the left innominate vein. The abdominal part of the left channel received the following tributaries:

(1) about the middle of its transverse part, the right ovarian vein; (2) at the point where it turned downwards from its transverse part, the left renal vein, which had already received the left ovarian vein; and (8) at the point where it doubled back on itself in order to ascend, the ascending lumbar vein, which was of small size. The vena azygos minor and the left superior intercostal vein together formed a continuous vessel which gradually diminished in diameter from below up, and which received the eleven intercostal veins of the left side. The spinal branches of these intercostal veins were much enlarged.



Fig. 5. The principal veins in Case 4 (Case of obstructed hepatic portion of inferior vena cava).




The ilio-lumbar veins were large, especially the spinal branches. In the lumbar portion of the vertebral canal there were large venous channels lying outside the dura mater and on either side of the posterior common ligament. All the enlarged spinal branches mentioned were continuous with these chan- nels. Blood evidently passed from the common iliac veins to the ilio-lumbar veins, and along their spinal branches to the spinal branches of the intercostal veins by way of the vessels in the vertebral canal; a route was thus provided by which some of the blood from the lower extremities reached the superior _ caval system.

Large veins were also observed in the ventral abdominal wall, suggesting that blood may also have passed by way of the epigastric veins to the superior vena cava.

===Developmental Interpretation===

Viewing this case as a whole, we find that we have present two distinct groups of features.

On the one hand, there is continuity of the inferior vena cava, through the right and left channels described above, with the vena azygos major and the vena azygos minor respectively. This condition is due to enlargement of both the thoracic supracardinals, and has doubtless persisted from the early embry- onic stage at which these were continuous with the lumbar supracardinals. To explain this condition it is necessary, we believe, to assume that some ob- struction, incomplete and possibly temporary, of the hepatic part of the in- ferior vena cava was present at the early embryonic stage just mentioned. This explanation also accounts for the continuity of the vena azygos minor with the left superior intercostal vein, this continuous channel being necessary for the conveyance of blood back to the heart.

The principal vessels present are interpreted as follows in terms of their embryological constituents (fig. 1): The postrenal part of the inferior vena cava is normal and includes the right lumbar supracardinal. The right channel, including the vena azygos major, consists of (1) the right thoracic supracardinal and (2) the cranial end of the right postcardinal. The left channel may be re- garded as formed by (1) the right supracardino-subcardinal anastomosis, (2) the intersubcardinal anastomosis, (8) the left supracardino-subcardinal anastomosis, (4) the left thoracic supracardinal, and (5) the cranial end of the left postcardinal. The transverse anastomoses connecting the vena azygos major and the vena azygos minor represent four of the thoracic intersupra- cardinal anastomoses which have persisted.

On the other hand, we have present (1) the fibrous cord representing the obliterated part of the inferior vena cava, and (2) the enlarged spinal and abdominal veins. These features, especially the latter, are characteristic of inferior caval obstruction! and together point to the obstruction having be- come complete and permanent either postnatally or at any rate in later foetal life. Had permanent obstruction occurred at the early embryonic period at which the lumbar and thoracic supracardinals were continuous, the obstructed part would, as is characteristic of both arteries and veins which disappear at such early periods, have become absorbed completely and could not have per- sisted as a fibrous cord showing traces of a lumen.

In this case, therefore, we believe (1) that incomplete and possibly tem- porary obstruction of the hepatic part of the inferior vena cava occurred at an early embryonic stage and resulted in the right and left channels connecting the inferior vena cava with the azygos veins; and (2) that either postnatally or at some late stage in utero the obstruction became complete and permanent, resulting in the enlargement of the superficial abdominal and spinal veins and probably also in further enlargement of the persistent developmental connec- tions.

==Bibliography of Anomalies of the Inferior Vena Cava and Azygos Veins in Man==

In studying and classifying anomalies of the inferior vena cava, it has been found impossible to exclude entirely anomalies of the azygos system, owing to the close developmental relationship of the two systems. An attempt has been made to classify the cases as left inferior vena cava, double inferior vena cava, etc., but here again, it is difficult to define the different types. For this reason some overlapping will be observed, and the cases have been placed in what seems the most suitable class. Those cases that cannot definitely be placed in one or the other of the following groups have been placed at the end under the title, ‘‘ Miscellaneous,” often because the details were insufficient, or because the original descriptions were not available.

===Double Inferior Vena Cava===

(1) Cambridge Anomaly Book. See Journal of Anatomy and Physiology, vol. xxxv, p. 123. Case 1. Double postrenal inferior vena cava with small communication with vena azygos major. Case 2. Double postrenal inferior vena cava. (2) Gfrarp, G. (1903). Bibliogr. Anat. t. x11, p. 293; see Anat. Anzeig. Bd. xm, S. 347. Apparently double inferior vena cava (no further details available). (3) Gorron (1900). Bull. Soc. Anat. de Paris, p. 691. (See Journ. Anat. and Physiol. vol. xxxv, p. 504.) Double inferior vena cava. (4) Koriman, J. Anat. Anzeig. Bd. vim, 8S. 97. Double inferior vena cava (good bibliography). Anat. Anzeig. Bd. vim, S. 104. Double inferior vena cava continuous with vena azygos minor which joins vena azygos major in usual way. (6) Lucas, M. F. Journ. of Anat. vol. 11, p. 69. Double postrenal inferior vena cava. (7) Marttn (1852). Monatschrift fiir Geburtskunde, Bd. xx. See Journ. of Anat. and Physiol. vol. xxxv, p. 13. Persistence of thoracic and lumbar cardinals in each side. (It is not clear whether post- cardinals or supracardinals.) (8) Metisstnos. Anat. Anzeig. Bd. xxxrx, S. 149. Double postrenal inferior vena cava, both trunks on the right side, right supracardinal and right postcardinal persistent. (9) Nicoxat, N. (1886). Diss. med. Kiel. See Anat. Anzeig. Bd. xu, S. 348. Two cases of partial doubling of inferior vena cava. (10) OsLER, W. Journ. of Anat. and Physiol. vol. xm, p. 291. Postrenally, double inferior vena cava. Prerenally, obliteration of hepatic portion of in- ferior vena cava; blood reaches heart via azygos system. (11) Paneratz (1894). Ueb. d. sogen. Verdoppelung d. ob. und unt. Hohlvene. Konigsberg. (12) Parren, C. J. Anat. Anzeig. Bd. xxxiv, S. 189. Double postrenal inferior vena cava. (13) Riscusretu, H. Journ. of Anat. and Physiol. vol. xuvm1, p. 287. Double postrenal inferior vena cava. (14) SHepHzrp, F. J. Journ. of Anat. and Physiol. vol. xxiv, p. 71. Double postrenal inferior vena cava. (15) Watrer, J. (1884). Diss. med. Erlangen. See Anat. Anzeig. Bd. xim, S. 348. Partial doubling of inferior vena cava. (16) Waxtiy, I. E. Anat. Rec. vol. xx, p. 95. Double postrenal inferior vena cava. (17) Watrerston, D. Journ. of Anat. and Physiol. vol. xLvu, p. 433. Double inferior vena cava. (18) Srimpa, L. Anat. Anzeig. Bd. vim, S. 655. (19) Grouper, W. (1859). Mém de Acad. Imp. des sc. de St Pétersbourg, t. u, p. 25. See Anat. Anzeig. Bd. vim, 8. 113. (20) —— (1880). Arch. f. path. Anatomie, Bd. txxx1, S. 465. See Anat. Anzeig. Bd. vim, S. 113. (21) —— (1881). Arch. f. path. Anatomie, Bd. Lxxxvi, 8. 493. See Anat. Anzeig. Bd. vm, S. 113. (22) Kapyz (1881). Wiener med. Jahrbiicher, Jabrgang, S. 40. See Anat. Anzeig. Bd. vam, S. 114. (28) Zaaorsky, P. (1822). Mém. de ? Acad. Imp. des sc. de St Pétersbourg, t. vit, S. 288. See Anat. Anzeig. Bd. vim, S. 116. (24) Lauber, H. Anat. Anzeig. Bd. x1x, S. 590. See also Journ. of Anat. and Physiol. vol. xxxvi, p. 305. Double postrenal inferior vena cava with small normal prerenal inferior vena cava. The main channel by which blood reaches the heart is an enlarged vena azygos major. Left Inferior Vena Cava (1) Auren, V. Anat. Anzeig. Bd. xii, 8. 337. A case similar to that described by us. The small persistent right supracardinal is in addition continuous with the vena azygos major. (2) Dorscx# (1858). Bayer. Aerz. Intelligenzblatt, no. 20. See Journ. of Anat. and Physiol. vol. XXXV, p. 15. Left prerenal and postrenal inferior vena cava continuous. (3) FRaNnKEL, W. Anat. Anzeig. Bd. xxxvu, S. 240. Left postrenal inferior vena cava. (4) Gzora, H. (1906). Diss. med. Miinchen. See Anat. Anzeig. Bd. xt, S. 347. Persistent left cardinal. (5) Gérarp, G. (1906). Bibliogr. Anat. t. xv, p. 85. See Anat. Anzeig. Bd. xim, S. 347. Persistent left postrenal cardinal (we have not been able to ascertain whether supracardinal or postcardinal). . (6) Guapstong, R. J. Journ. of Anat. and Physiol. vol. xtvi, p. 220. Left postrenal inferior vena cava crossing over and becoming normal prerenally. There are also two small vessels running between inferior vena cava and vena azygos major. (7) GrimspaLe. Journ. of Anat. and Physiol. vol. xxvm, p. 5. Left postrenal inferior vena cava. (8) M’Wuunnre (1840). London Med. Gaz. March 27th, p. 31. See Journ. of Anat. and Physiol. vol. xxxv, p. 15. The two common iliac veins unite at first lumbar level on the left side and resultant vessel continues on the left side. Situs inversus viscerum. 


1 For an excellent and extensive account of inferior caval obstruction, see article by J. Hall Pleasants in Johns Hopkins Hospital Reports, vol. xv, p. 363. Four Cases of Anomalous Inferior Vena Cava 195


(9) NeuBercer, H. Anat. Anzeig. Bd. xim, S. 65. Left postrenal inferior vena cava becomes continuous with vena azygos major. (10) Parerson, A. M. Journ. of Anat. and Physiol. vol. xxxv, p. lviii. Left postrenal inferior vena cava crossing over to become normal prerenal inferior vena cava. There is also a vessel connecting the two renal veins behind the aorta. (11) Rauman, M. A. Journ. of Anat. vol. Lt, p. 307. Left prerenal and postrenal inferior vena cava with transposition of viscera. (12) ReveEui, D. G. Amer. Journ. of Anat. vol. 1, p. xvi. Left postrenal inferior vena cava joining up with vena azygos minor, crosses over to join vena azygos major in usual way. Also there was a small postrenal supracardinal. (13) SrrutHErs. Journ. of Anat. and Physiol. vol. xxvu, p. vi. Left postrenal inferior vena cava crossing to become normal prerenal inferior vena cava. (14) Warine, H. J. Journ. of Anat. and Physiol. vol. xxvii, p. 46. Similar to case above (no. 13).

===Combined Anomalies of Inferior Vena Cava and Azygos System===

(1) ABERNETHY (1793). Phil. Trans. Royal Soc. London, pt. 1.

Persistent right cardinal probably continuous with azygos system. (2) CaRPENTIER and BerTavx (1888). Arch. de Physiol. norm. et path. p. 79.

Persistent right cardinal. Prerenal inferior vena cava continuous with azygos system. (3) CruvemHier. Traité d Anatomie Descriptive, t. m1, 4th ed. p. 223.

Normal postrenal inferior vena cava crossing to left prerenally, and becoming continuous with an enlarged vena azygos minor which again crosses to right to enter vena azygos major in the usual manner.

(4) Horner (1817 and 1818). Journ. of Acad. of Philadelphia.

Same as no. 2 (case of Carpentier and Bertaux).

(5) Kamemeter, O. F. Anat. Record, vol. x1x, p. 361.

Occlusion of right auricle resulting in complete closure of mouth of superior vena cava, 80

that blood flowed down via azygos system to enter inferior vena cava at level of diaphragm. (6) Kios (1859). Zeitschrift d. Kaiser. Gesellsch. der Aerzte zu Wien, Bd. xv, S. 733, vide Schmidt’s Jahrbicher.

Persistent right cardinal probably continuous with vena azygos major.

(7) Pauxus (1842). Ost. Med. Wochenschrift, Bd. 1, S. 313, vide Canstatt’s Jahresbericht.

Same as no. 6 (Klob’s case).

Note. For no.’s 1, 2, 3, 4, 6, and 7, see T. Dwight’s article, Journ. of Anat. and Physiol. vol. XXxXvV, p. 7.

Miscellaneous

(1) Cambridge Anomaly Book. See Journ. of Anat. and Physiol. vol. xxxv, p. 124, no. 3. Normal inferior vena cava with small persistent left supracardinal. (2) Cambridge Anomaly Book. See Journ. of Anat. and Physiol. vol. xxxv, p. 124, no. 4. Inferior vena cava normal as far as liver where it was greatly contracted and reached the heart as a very small vein. Main channel for blood was via vena azygos major with which inferior vena cava was continuous. (3) Cameron, J. Journ. of Anat. and Physiol. vol. xv, p. 416. Normal inferior vena cava with small persistent left supracardinal. (4) Dwiext, T. Journ. of Anat. and Physiol. vol. xxxv, p. 7. Left inferior vena cava continuous with vena azygos minor, which crossed as usual to join vena azygos major, which however was much enlarged as was the vena azygos minor. (5) G&rarp, G. (1908). Bibliogr. Anat. t. xvi, p. 227. See Anat. Anzeig. Bd. xim, S. 347. Unusual anomaly of the inferior vena cava. (6) Geruacn, L. (1885). Sitz. der Physic. med. Societat zu Erlangen. Sitz. V. 12 Jan. 1885. See Anat. Anzeig. Bd. vin, 8. 113. (7) Guapstone, R. J. Journ. of Anat. vol. xLv, p. 225. Persistent true postcardinal with ureter passing round it. Four Cases of Anomalous Inferior Vena Cava 197

(8) GrirritH, T. W. See Journ. of Anat. and Physiol. vol. xxx, p. 503. Article is in the “Scalpel” for Jan. 1899, vol. rv, p. 13. Description of two cases of obstructed inferior vena cava, in one of which blood was returned to the heart via azygos system. Journ. of Anat. and Physiol. vol. xxvi, p. 117. Absence of hepatic portion of inferior vena cava. Blood returned to the heart via azygos system. Also situs inversus viscerum. (10) Hocusretrer (1893). Morph. Jahrbich. Bd. xx. See Journ. of Anat. and Physiol. vol. xxxv, p. 15. (11) Jounston, T. B. Journ. of Anat. and Physiol. vol. xtvut, p. 235. Normal right inferior vena cava with small persistent left supracardinal. (12) Koxisxo, F. Anat. Anzeig. Bd. xxxtv, S. 520. Right ureter passing round a persistent right postcardinal. (13) Lawrence, T. W. P. and D. NaBarro. Journ. of Anat. and Physiol. vol. xxxvi, p. 63. Absence of hepatic portion of inferior vena cava. (14) Ponsot, J. (1857). Mémoires de la Soc. de Biologie, 1856, p. 195, Paris. See Anat. Anzeig. Bd. vim, 8. 115.

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