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XVII. On the Development of the Ductless Glands in the Chich. 
By Henry Gray, Esq., F.R.S., Demonstrator of Anatomy at St. George's Hospital. 
Communicated hy William Bowman, Esq., F.R.S. 
Received November 12. 1851, — Read January 15, 1852. 
Having been engaged for some period in investigating the evolution of the 
spleen, supra-renal and thyroid glands, and the several tissues of which each is com- 
posed, and having arrived at some conclusions which differ from those previously 
given, I have ventured to lay them before the Royal Society. 
Development of the Spleen. 
Before describing the results of my own investigations, I may mention that 
Arnold* states that the spleen arises like the pancreas from the duodenum, and 
exists at first as a common mass with that gland ; whilst Bischoff'I' believes that 
it arises from a mass of blastema, at first common both to this organ and the pan- 
creas, that forming the pancreas proceeding from the duodenum, and that of the 
spleen from the great curvature of the stomach. 
I'he description which I now propose to offer, differs from either of those above 
mentioned. 
About the seventy-second hour (Plate XXL fig. 1), I found in the embryo of the chick 
that the vitelline sac had already sufficiently contracted to form two canals, of which 
the posterior was small, and only just observable; but the anterior one was much 
larger and longer, and took a somewhat tortuous course through the body of the 
embryo. No trace of either pancreas or spleen is yet to be observed, but a conical 
protrusion from the inferior part of this tube indicates the first rudiment of the liver. 
At the ninetieth hour (fig. 2) the anterior of the two canals is longer and narrower 
than the posterior ; it presents two slight dilatations, the first in the situation where 
the liver and pancreas are developed, the second, and larger, immediately in front of 
this, indicating the position of the future stomach. It is at the first-mentioned dila- 
tation, at its upper part, and behind the stomach, that the pancreas is developed. 
This rudimentary gland, at this period, consists of a flask-shaped mass of dark 
granular blastema, connected by a broad peduncle with the wall of the intestinal 
tube, from which it is apparently a protrusion, being of a similar structure with it. 
That part connected with the intestine is narrow and tubular, its distal portion being 
* F. Aexold, Salz. Med. Zeitung, 1831, T. W. p. 301. 
t T. L. Bischoff, Entwick. der Saiigthiere und des Menschen. Leipzig, 1842, p. 285. 
MDCCCLII. 2 Q 
