638 
MR. J. GOODSIR ON THE SUPRA-RENAL, 
with blood-vessels to convey the blood to and from the part, and with lymphatics 
which receive the product of solution of the cells, and convey it back again into the 
general circulation, whence it was originally derived. 
The account of the structure of the thymus given by Sir Astley Cooper, is so far 
incorrect, as this organ contains no reservoirs or cavities in its substance. The cavi- 
ties exhibited by Sir Astley Cooper in his drawings and preparations, are the results 
of modes of preparing. They are artificial cavities formed by distension, between 
the somewhat smooth, highly vascular, and slightly adhering outer surfaces of con- 
tiguous lobules ; the whole organ being at the same time bound together by a stronger 
external areolar texture. No milky fluid is found naturally in these interlobular 
spaces. Indeed Sir Astley Cooper says, that “ the best mode of obtaining it, is by 
cutting the gland into very small pieces and placing them upon gauze, which being 
squeezed, the solid is separated from the fluid part, and the latter escapes through 
the gauze.” 
The thymus, from the time it assumes its most perfect structure till it begins to 
degenerate into fatty substance, consists of lobes connected by areolar fibres, without 
cavities or ducts, formed of nucleated cells grouped around germinal spots, deriving 
matter for the formation of their cells from arteries passing into it, and being re- 
lieved of its venous blood by returning veins, being plentifully supplied with lym- 
phatics, which do not communicate with the supposed reservoirs, as has been sug- 
gested, but appear to take their origin, as in other parts, by intercellular lacunae, in 
which the walls seem gradually to lose themselves, as the ducts of the liver are lost 
among the secreting cells of that organ. 
The thyroid body possesses a structure which is essentially the same as that of the 
thymus. It differs from the thymus in not being divided into lobules, in having the 
groups of cells of which it consists separated from one another by moderately strong 
capsular membranes, and in being more vascular, the anterior and venous trunks 
being much larger. 
The supra-renal capsules also consist of nucleated cells grouped round germinal 
spots, and arranged, not in lobules, but in columns passing towards the surface of the 
organs ; an arrangement corresponding to the radiating direction of the veins, and 
the converging arteries of these parts. The supra-renal and thyroid bodies are more 
vascular than the thymus from being developed around large arteries, while the 
thymus is in connection with smaller trunks, the former being developed in connec- 
tion with the first and second aortic arches and the omphalo-mesenteric vessels ; the 
latter in connexion with the internal mammary arteries and other small thoracic and 
cervical branches. The greater density of the areolar capsule of the thyroid may 
probably be explained by this increased vascular supply. 
That portion of the membrana intermedia which is separated from the rest of the 
membrane, and included in the body of the embryo by the umbilical constriction, 
and which has not already been devoted to the formation of the heart, liver, pancreas 
