424 THE ORIGIN OF VERTEBRATES 
called suprarenal; a segmental series of paired organs, each of which 
possesses a branch from the aorta and a sympathetic ganglion, and an 
unpaired series in close connection with the kidneys, to which Balfour 
gave the name of interrenal glands. Of these two sets of glands, 
Swale Vincent has shown that the extract of the interrenals has no 
marked physiological effect, in this respect resembling the extract of 
the cortical part of the mammalian gland, while the extract of the 
paired segmental organs of the Elasmobranch produces the same 
remarkable rise of blood-pressure as the extract of the medullary 
portion of the mammalian gland. 
The development also of these two sets of glands is asserted to be 
different. Balfour considered that the suprarenals were derived from 
sympathetic ganglion-cells, but left the origin of the interrenals 
doubtful. Weldon showed that the cortical part of the suprarenals 
in the lizard was derived from the wall of the glomerulus of a 
number of mesonephric tubules. In Pristiurus, he stated that the 
mesoblastic rudiment described by Balfour as giving origin to the 
interrenals is derived from a diverticulum of each segmental tubule, 
close to the narrowing of its funnel-shaped opening into the body- 
cavity. With respect to the paired suprarenals he was unable to 
speak positively, but doubted whether they were derived entirely 
from sympathetic ganglia. 
Weldon sums up the results of his observations by saying: 
“That all vertebrates except Amphioxus have a portion of the 
kidney modified for some unknown purpose not connected with 
excretion ; that in Cyclostomes the pronephros alone is so modified, 
in Teleostei the pro- and part of the meso-nephros; while in the 
Elasmobranchs and the higher vertebrates the mesonephros alone 
gives rise to this organ, which has also in these forms acquired a 
secondary connection with certain of the sympathetic ganglia.” 
Since Weldon’s paper, a large amount of literature on the origin 
of the adrenals has appeared, a summary of which, up to 1891, is 
given by Hans Rabl in his paper, and a further summary by Aichel 
in his paper published in 1900. The result of the investigations up 
to this latter paper may be summed up by saying that the adrenals, 
using this term to include all these organs of whatever kind, are in 
all cases, partly at all events, derived from some part of the walls of 
either the mesonephric or pronephric excretory organs, but that in 
addition a separate origin from the sympathetic nervous system must 
