XII BLOOD GLANDS 347 
the median line between the two kidneys, or is unsymmetrically 
placed on the ventral surface of either kidney.’ Sometimes (e.g. 
in Raia) the inter-renals are paired, in which case they are applied 
to the inner and hinder margins of the kidneys. In the Sturgeon 
(Acipenser sturio) the “supra-renals” appear as numerous “ ochre- 
yellow ” bodies, variable in size and distribution (Fig. 203, B). 
Some of them are visible on the surface of the kidneys, while 
others are scattered about in their substance, but on the whole 
are more anteriorly placed than in Teleosts. In the latter group 
the “supra-renals” are usually two in number (Fig. 203, C), but 
may be as many as five or reduced to one. They are disposed 
either on the ventral or the dorsal surface of the kidneys, 
generally near their hinder extremities, or more or less deeply 
embedded in their substance. Besides these bodies there are 
also chromaffin cells in the walls of the anterior cardinal veins.” 
Histologically, the paired segmentally arranged bodies of 
Elasmobranchs differ considerably in structure from the inter- 
renal bodies, the former resembling the “ medulla,’ while the 
inter-renals, as well as the so-called supra-renals of <Acipenser, 
exhibit a striking resemblance to the alveolar “cortical” sub- 
stance of the Mammalian supra-renals.? In Cyclostomes the 
cortex is apparently represented by the lobules of cells along the 
posterior cardinal veins and the medulla by the “chromaffin ” 
cells, while in Teleosts the cortex and the medulla have their 
respective counterparts in the supra-renals and the “ chromaffin ” 
cells in the walls of the anterior cardinal veins. It may be 
concluded, therefore, that Elasmobranchs, Cyclostomes, and 
Teleosts possess anatomically distinct representatives of both the 
“medulla” and “cortex” of Mammalia, although the Sturgeon 
is at present only known to possess the equivalent of the 
“cortex.” In Amphibia, Reptilia, and Aves both “cortex” and 
“medulla” are present, and in the varying intimacy of their 
relations offer a transition to the Mammalian arrangement of a 
central medulla closely invested by a sheath of cortical substance. 
A more or less intimate connexion exists between the paired 
supra-renals of Elasmobranchs and the sympathetic nervous 
1 Vincent, Trans. Zool. Soc. xiv. Part iii 1897, p. 41. For bibliography see 
Vincent, Internat. Monatsschr. f. Anat. u. Phys. xv. 1898, p. 319. 
2 Giacomini, quoted by Swale Vincent, Journ. Anat. and Phys. xxxviii. 1903, 
p. 41. 
3 Vincent; op. cit. pp. 32, 33. 
