352 The Histogenesis of the Adrenal in the Pig 
selachians he concludes that the so-called suprarenal bodies, which, since 
Balfour’s work, have generally been considered as derivatives of the 
sympathetic ganglia, are really derived from retrograding canals of the 
Wolftian body; and that the interrenal body, the supposed mesoblastic 
anlage of the adrenal, is laid down by the peritoneal invaginations 
(Trichter) of the same body. The interrenal body, alone, he says, is 
the homologue of the adrenal of higher animals. Along with these 
considerations of phylogenesis he gives a careful study of the early de- 
velopment of the adrenal in rabbits and moles. In the former animal 
he finds the first evidence of the adrenal anlage in an embryo 6.5 mm. 
long. It consists of an invagination of the coelomic epithelium on each 
side of the attachment of the mesentery corresponding to the region of 
the anterior third of the Wolffian body. He describes and figures such 
invaginations as running dorsalward to end in small groups of cells 
which present numerous mitotic figures. These invaginations have 
nothing to do with the genital ridge, he thinks, but occur too far for- 
ward to be connected with that structure. Moreover, the epithelium at 
the site of the invaginations shows no differentiation, nor does it pre- 
sent any evidence of cell division. These observations lead him to con- 
clude that the invaginations are the remnants of Wolffian body “ Trich- 
ter,’ which body, he says, is already undergoing retrogressive changes 
in this region (anterior third). Accordingly, the anlage of the adrenal 
cortex in the rabbit is derived from atrophying Wolffian body invagina- 
tions. 
In the case of the mole, although he had an excellent series of em- 
bryos at his disposal, Aichel was unable to find any such coelomic invagi- 
nations as those described in the rabbit; the earliest evidence of the 
adrenal was a small mass of cells undergoing active karyokinesis in the 
mesenchyme. In the vicinity he could find some cross sections of 
tubules which he considered remnants of the Wolffian body, but they 
had no connection with the anlage of the adrenal. Accordingly, it would 
appear that in the mole the adrenal arises free in the mesenchyme. Never- 
theless Aichel thinks that the ultimate source of the anlage is the same 
as in the rabbit, although he could not demonstrate such an origin in a 
well-nigh perfect series of embryos. 
As to the origin of the medulla of the gland, he states, without giving 
an account of his observations thereon, that the medulla is derived from 
the same source as the cortex. 
Josef Wiesel “ employed pig embryos 1 cm., 2 cm., 2.5 cm. and 3 cm. 
10 Ueber die Entwickelung der Nebenniere des Schweines besonders der Marksub- 
stanz. Anat. Hefte, Wiesb., 1901, Bd. XVI, 8S. 115-150. 
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