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XXIX. On the Supt'a-renal, Thymus and Thyroid Bodies. 
By John Goodsir, Esq. Communicated by Richard Owen, Esq., F.R.S., fyc. 
Received June 19, 1845, — Read January 22, 1846. 
While engaged, two years ago, in observing the structure of the lymphatic 
glands, my attention was directed to the thymus, thyroid, and supra-renal bodies ; 
and I was led to frame a hypothesis, which, although afterwards requiring some 
modification, has, I conceive, nevertheless enabled me to detect, if not the real phy- 
siological, at least the morphological signification of these apparently anomalous 
organs. 
My hypothesis was, that the thyroid, thymus and supra-renal bodies are the re- 
mains of the blastoderma ; the thyroid being a portion of the original cellular sub- 
stance of the germinal membrane grouped around the two principal branches of 
the omphalo-mesenteric vein ; the supra-renal capsules, constituting other portions 
grouped around the omphalo-mesenteric arteries ; and the thymus, the intermediate 
portion of the same membrane arranged along the sides of the embryonic visceral 
cavity. 
Subsequent observations have satisfied me that this hypothesis is essentially cor- 
rect, with the exception of that part of it relating to the thyroid, which body I have 
now ascertained to be a portion of the membrana intermedia of Reichert, which re- 
mains in connection with anastomosing vessels between the first and second aortic 
arches, or carotid and subclavian arteries. 
In the embryo of the Sheep, while the branchial clefts are still open, and for some 
time afterwards, there is a quantity of blastema arranged in minute lobular masses 
around the anterior parts of the cardinal veins of Rathke, surrounding the jugular 
veins and ductus G'uvieri for a short distance behind the fore-part of the Wolffian 
bodies. Immediately in front of the Wolffian bodies these lateral masses of blastema 
are narrow, being scarcely perceptible on the coats of the cardinal veins ; but around 
the ductus Cuvieri they are larger, and differ from the general texture of the 
embryo, in having a darker colour, in containing no fibres, in separating readily 
from the surrounding parts, and in their lobulated appearance. They extend for- 
wards nearly to the base of the cranium, and are not connected across the median 
plain. They are broadest at the sides of the heart, and when the pericardium is 
opened, are seen through its posterior wall occupying the future situations of the 
lungs, which at the period stated exist as two small lobulated white bodies, project- 
ing from the intestinal tube, behind and below the heart. 
4 N 
MDCCCXLVI. 
