130 
DR. C. H. JONES ON THE STRUCTURE 
yet been correctly described. On the fifth day the constriction of the germinal 
membrane producing the vitelline duct was perfectly manifest, and the duct itself 
was filled with a dark oily mass contained in a distinct homogeneous membrane ; this 
membrane constituting a complete sheath separated the cavity of the vitelline duct 
from that of the abdomen. It divided into two canals which took their course in 
nearly opposite directions ; one ran forward and turned sharply upwards just behind 
the liver, and soon expanded into a somewhat dilated cavity. From this cavity several 
offsets were distinctly traced ; one inclined upwards and a little forwards, widening 
as it proceeded, and soon opened into a transparent space with delicate but distinct 
parietes, which was evidently the stomach, as it opened at the other extremity into 
the oesophagus. A second offset, which was very distinct, passed upwards and back- 
wards, and appeared to terminate in a cul de sac, but its destination could not be 
satisfactorily determined. From the anterior part of the intestinal cavity two less 
distinct offsets could be clearly traced proceeding into the liver ; the upper one ap- 
peared to divide, but they could not be seen to ramify in the substance of the gland. 
The other canal proceeding from the vitelline duct ran backwards and upwards, and 
seemed clearly to be developing itself into the posterior part of the intestine, but was 
in a less advanced condition than that already described ; at a subsequent period 
the two cseca, which afterwards attain so considerable a length, were seen sprouting 
out on either side from this portion of the intestine. Both these canals derived from 
the vitelline duct were filled with opake oily contents, so that their course was most 
satisfactorily traced ; they also presented a distinct homogeneous enveloping mem- 
brane, and some trace of an external layer of granular aspect which afterwards be- 
comes much more marked, and which seems to be derived from the germinal mem- 
brane itself. 
Towards the close of the sixth day a change had taken place in the condition of 
the stomach ; it no longer distinctly communicated with the developing intestine, but 
appeared as a thick well-defined mass, into which the canal of the oesophagus ran, 
and terminated by a marked csecal dilatation. The anterior prolongation of the vitel- 
line duct formed a considerable curve with the convexity upwards, then descending 
became indistinct, and terminated near the lower convex border of the liver. Shortly 
before its termination, it gave off towards the liver a bulging process, which exhibited 
some traces of dividing, but did not nearly reach the margin of the gland ; a circum- 
stance which greatly surprised me, as I had fully expected that these offsets from the 
intestine to the liver would have proceeded to develope themselves into the hepatic 
duct, and not have retrograded as they thus appeared to do. Towards the end of the 
seventh day the stomach is completed and overlapped by the two lobes of the liver; 
the duodenal loop is also distinctly formed ; in its concavity there is seen a curved 
elongated tract, which stretches up to the hilus of the liver and is there somewhat 
enlarged ; it consists of cells, granular matter and nuclei, with an oily blastema, and 
is clearly the rudiment of the pancreas ; as yet it has no connection with the intes- 
