296 
MR. H. GRAY ON THE DEVELOPMENT OF THE 
spherical, and its surface slightly lobulated. There is no trace of any subdivision ot 
this body into two portions, nor at its distal end can any trace of a spleen be as yet 
observed. Nearly the whole length of the above mentioned two canals have con- 
nected with them above a delicate fold of membrane, the “ intestinal lamina,” which 
serves to connect them with the vertebral column beneath. At the 114th hour 
(fig. 3) the anterior prolongation of the vitelline sac presents a double curvature, the 
concavity of one being directed towards the under, the other towards the upper 
surface of the embryo ; it is in this latter that the rudimentary pancreas may now 
be clearly seen. This organ now appears as an elongate, dark granular, tubular 
mass, situated in that curved portion of the intestinal canal which is the rudiment 
of the duodenum ; its direction is in the transverse axis of the embryo, one extremity 
being connected to the primitive intestinal tube, into which it may be seen to open 
by a distinct tubular prolongation, the other being separated from the spleen by a 
distinct granular blastema ; its margins are not very distinct, and its contents and 
wall are darkly granular. The spleen makes its first appearance at this period in a 
fold of the “intestinal lamina,” which below is continuous with the edge of the 
intestine, as far as the constricted portion of the vitellary sac, and above with the 
lower part of the rudimentary stomach. It is a small oval whitish mass, situated 
near to the distal end of the pancreas, but perfectly separate from this body. This 
separation is more evident at this period than at any other of its first stages of 
development ; for a distinct granular membrane now divides them, whilst also the 
dark granular tinge of the pancreatic mass, and the lighter colour of the rudimentary 
spleen make this distinction more manifest. At a more advanced period of their 
development, the increased size of both organs causes them to approximate more 
closely, although not more intimately to one another, and it is this latter circum- 
stance that has given rise to the great difference of opinion regarding the develop- 
ment of these parts. The organ, which has now a greyish tinge, lies parallel with 
the body, and tapers at both ends, the lower one being connected with the fold of 
the blastema, attached below to the intestine and vitellary membrane, the upper 
one continuous with the upper part of the same fold, which passes to the surface of 
the rudimentary stomach. On the fifth day (fig. 4) the pancreas and spleen may 
still be observed as two separate and independent masses of blastema, the former of 
which forms a distinct opake transverse tract of white matter, which stretches 
upwards and backwards from the rudimentary duodenal loop, the spleen existing as 
a reddish round mass occupying its opposite extremity. The rudimentary pancreas 
is elongated, and presents an indistinct external margin, which is somewhat convo- 
luted. From the end, near the centre of that curvature of the canal which would 
correspond to the duodenum, an offset is given off, which consists of a dark narrow 
tube with very distinct margins, communicating with the dark margin of the canal 
itself. This I believe to be the rudiment of the pancreatic duct. The spleen at this 
period consists of a dark mass of blastema, distinct from all the surrounding parts ; 
