634 
MR. J. GOODSIR ON THE SUPRA-RENAL, 
These two lateral masses are the only remaining portions of the membrana in- 
termedia : the posterior portion on each side, on the inner aspect of the anterior ex- 
tremity of the Wolffian body, becomes the supra-renal capsule; the enlarged middle 
portion and the outer part of the cervical portion become the thymus ; while the 
internal anterior part resolves itself into the thyroid body. These three organs are 
therefore at this period continuous with one another on each side of the middle line, 
no isthmus having yet been formed. They are also continuous with the Wolffian 
bodies ; these bodies, the supra-renal capsule, the thymus and the thyroid forming 
a continuous mass, situated in the elongated angular channel, which stretches from 
the cranium to the coccyx on the outside of the intestinal or mesenteric laminae, 
and between them and the visceral laminae. 
The Wolffian bodies are the last organs formed out of the membrana intermedia, 
which assume a special structure. The supra-renal capsules, the thymus and thyroid, 
retain throughout their existence the original texture of the blastoderma. 
Proceeding therefore in the order of formation as well as of position from the 
Wolffian body, I shall state very briefly what I have observed concerning the mode 
of development of the supra-renal capsules, thymus and thyroid. 
In the embryo of the Sheep, in which the branchial clefts are still quite open, the 
omphalo-mesenteric vessels well-developed, the liver consisting of an equal-sized 
lobe on each side of the intestinal tube, the Wolffian bodies well-formed, the allantois 
beginning to protrude from the abdomen, and the umbilical vessels already apparent, 
there may be seen between the internal anterior part of the Wolffian bodies and the 
aorta at the origin of the omphalo-mesenteric arteries, and also around the omphalo- 
mesenteric vein, where that vessel is passing forward into the liver, a mass of blas- 
tema spread over the internal surface of the fore-part of the Wolffian body, and 
arranged in one or more masses between that gland and the aorta. 
In embrvos rather more advanced, these masses of blastema become less distinct, 
apparently from their increased bulk causing them to be applied more uniformly 
over the anterior extremities of the Wolffian bodies. They may always be detected 
by their whiter appearance, and by being destitute of the cross markings produced 
by the ducts of the Wolffian glands. 
It is not till the testes, ovaries and kidneys have appeared, that the supra-renal 
capsules are recognized as distinct organs ; and their progress after this period need 
not be considered further at present. 
The cardinal veins of Rathke pass forward along the posterior and lateral part of 
the Wolffian bodies ; after passing beyond the blunt anterior extremities of these bodies, 
each vein carries with it, or is covered by a thin layer of the blastema already alluded 
to, as forming at its posterior part the supra-renal capsule. This portion of the blas- 
tema becomes much larger at the side of the heart, round the ductus Cuvieri, behind 
the lateral parts of the pericardium, and in the future situation of the lungs, which 
have not yet left their median position. Each lateral portion of the blastema stretches 
