500 
Proceedings of the Royal Society 
lamina, taking a crescentic form continuously throughout, and after 
a valvular manner ending at the distance of three-sixteenths of an 
inch from the crest or rim of entrance of the superior vena cava. 
After alluding, secondly , to the significant case shown and 
described to the Society on the 4th ult, by Professor Turner, Dr 
Handyside showed (fig. 2), and gave a sketch of — 
Thirdly , another specimen from his rooms, which presents on 
the posterior wall, and at the rim of entrance, of the superior cava 
a well defined and deep lacuna, within which open five large The- 
besian foramina. The caval half of the patulous border of this 
lacuna is protected by an oblique semilunar valve, one quarter of 
an-inch in breadth and of a like depth. This valve is composed 
of a duplicature of endocardium, and is evidently designed to 
secure the entrance of blood into the auricle.* 
The author next compared shortly these three abnormal cases, 
demonstrating how they formed at once a graduated scale or an- 
atomical series mutually illustrative, each specimen introducing 
to the mind its own peculiar features of morphological interest. 
He considered, however, these cases as chiefly interesting — when 
compared with the results of certain changes undergone by the 
human embryo between the third and the seventeenth weeks after 
conception — in relation with the structural affinities they present 
to permanently impressed forms in some cold and warm-blooded 
* The additional sketches, figs. 3 and 4, represent peculiarities in two 
adult hearts, and fig. 5, in a foetal heart, dissected in Dr Handyside’s rooms. 
In fig. 3 a valve (| inch broad by £ inch deep), formed of endocardium with 
an intervening lamina of striped muscle, lay within and parallel to the pos - 
terior segment of the rim of the superior cava. In fig. 4 is an unusually 
large persistent Eustachian valve, continuous at its left insertion with a still 
more remarkable Thebesian valve. The former, which is very large, has an 
insulated fibrous offset from its left extremity, which runs' half-way across 
the sinus venosus towards the tubercle of Lower, and then dichotomously 
divides and subdivides thrice before it is implanted into the arched lino 
between the right cornu of the Eustachian valve and the right segment of 
the rim of the superior cava. Fig. 5 represents, in a male foetus of 6 J months, 
presented to Dr Handyside’s museum during last summer, the occurrence of a 
complete semilunar valve situated at the termination of the upper vena cava, 
its convex border being attached to the anterior and right wall of the vein, its 
concave free border projecting into the auricle. The right crus of this valve 
is inserted into the auricular wall on a plane { of an inch behind, and de- 
cussating, the right ascending cornu of the prolonged Eustachian valve. 
