164 
MR. MARSHALL ON THE DEVELOPMENT 
parently blending with those of both auricles. There are no valves along its course, 
but the mouth of each of its cardiac branches is guarded with a fine valve, that of 
the coronary vein being the largest. The wide orifice of the vessel into the right 
auricle is marked above, below and to the right, by a slight rim, but there is no 
Thebesian valve, the absence of which, in this and all the other examples of double 
vena cava superior in which the point is capable of being determined (Nos. 1, 4, 12, 30, 
31), suggests a comparison with the fact that it is also absent in those large quadru- 
peds which have a left vena cava superior or a left azygos venous trunk. The Eusta- 
chian valve is small and perforate ; its left cornu does not reach the lower border of 
the fossa ovalis, owing, as it were, to the intervention of the large orifice of the left 
superior cava. The foramen ovale is quite closed. 
The second example (No. 31) of double vena cava superior which I have to men- 
tion, occurred in the heart of a child between four and five years of age ; in the ven- 
tricular portion of which there are some defects. The auricles, however, are perfectly 
shut olf from each other. The lower part only of the left superior cava is present in 
the preparation, that vessel having been divided opposite the left pulmonary veins : 
it is very large and muscular, and receives the coronary and one other principal 
cardiac vein, the orifices of both being provided with valves. The opening of the 
vessel into the auricle is marked by a sharp border ; but, as in other cases, the 
Thebesian valve is wanting. So, too, is the Eustachian valve. 
b. JVith transposition . — There is, so far as I am aware, but one instance on record 
of the occurrence of double vena cava superior, together with transposition of the 
viscera. In this case the superadded vein is of course on the right side : a small vena 
azygos exists on that side, and ends in the right vena cava*. 
CLASS II. TRANSVERSE BRANCH WANTING. 
A failure in the preliminary step of the development of a cross branch in the neck 
necessarily implies the non-occlusion of either of the lateral primitive veins ; for, 
though two superior cavEe may coexist with the transverse communication in the 
neck, yet, when the latter is absent, each primitive vein must continue to return 
the blood from its own side of the upper half of the body. 
In such instances the characteristic cross branch of the mammalian venous system 
is wanting ; the condition of the great anterior veins is like that of birds ; and there 
is no metamorphosis excepting what is due to changes of size and position in the four 
simple lateral primitive veins typical of the vertebrate animal. Transposition has 
not been noticed in connection with this variety. 
The best illustration of deficiency of the cross branch occurs in a case (No. 2)'f' 
* Sir A. Cooper, in Dr. Watson’s paper, Medical Gazette, June 1836, p. 394. The specimen is now in 
the Museum of the Royal College of Surgeons. 
t No. 2. Bcehmee (Observ. Anat. rarior. fasciculi. Prsefat. p. xii.). Theune (De confluxu trium cavar. in 
cord, atrio dextro, &c. Halae, 1763, with a figure. Republished, Amsteld. 1764). 
