DUCTLESS GLANDS IN THE CHICK. 
297 
when seen with the naked eye it is of an opake white, or slightly reddish colour ; its 
shape is circular or reniform, and it is situated close to the end of the pancreas 
below and beneath the rudimentary stomach. The organ consists of part of a tract 
of blastema, which at the upper and lower extremities of the spleen are continued 
from it, in one direction, towards the lower end of the stomach, in the other, back- 
wards towards the intestine. It occupies the free margin of the fold of the “ intestinal 
lamina,” which presents a direction similar to what was observed on the fourth day 
of incubation. On the sixth day (fig. 5), the anterior prolongation of the vitelline 
duct forms two very considerable curves, the one nearest to the stomach, the con- 
vexity of which is directed downwards, having become completely developed into 
the duodenal loop, and in this loop the pancreas is plainly visible, the rudimentary 
spleen occupying its distal extremity. The position of these parts is now somewhat 
altered, passing obliquely upwards and backwards, instead of transversely, as on the 
fifth day. This appears to depend upon the alteration in the form and position of 
the intestine, which, being curved more upwards, would necessarily give to these 
parts a more oblique direction. The spleen is at this period distinctly visible to the 
naked eye, it is seen below and beneath the stomach ; its shape is reniform, being 
prolonged into two extremities, one at its upper, the other at its lower part ; it is 
situated at the edge of the fold of the intestinal lamina, which stretches from the 
lower end of the stomach across the intestine to the vitelline duct. The lower pro- 
longed extremity is the more distinct of the two, and is to be traced for some little 
distance along the margin and in the substance of this fold, being ultimately lost in 
it. The other extremity, or that connected to the stomach, is more rounded, and is 
connected through the interposition of the same fold of membrane to the lower part 
of the stomach itself. Its position is now somewhat altered, it being placed above 
and slightly behind the stomach ; its upper edge being on a level with the rudi- 
mentary proventriculus. At the point where the spleen was connected with the 
pancreas, an apparent continuity of substance was found between them ; but this 
was not really so, for the two organs were to be observed to be separate from one 
another, from the great difference in their texture, the substance of the rudimentary 
pancreas being darkly granular, whilst that of the spleen was of a lighter colour. 
On the seventh day (fig. 6) the spleen is of a patchy reddish tinge, from the presence 
of blood in its substance ; and its position is now precisely the same as in the adult 
bird, occupying the space at the back part of the proventriculus, which exists now 
as a separate and distinct pouch ; the surface of the organ is slightly lobulated, 
expecially towards its two extremities. It is now enclosed by a distinct membrane, 
and occupies the gastric surface of the distal end of the pancreas ; its shape is pyri- 
form, the rounded end being directed backwards and upwards, and the narrow end 
forwards, into the interval between the commencement of the duodenum and pan- 
creas ; these two extremities are still connected by folds of membrane with the 
stomach and mesentery ; they proceed from the back part of the organ, and apparently 
2 Q 2 
