SUPRARENAL GLAND—EFFECTS OF INANITION 271 
irregularity of arrangement of the cell cords in the zona reticularis 
is perhaps in part due to the pressure of the expanding medulla. 
In the rat, however, and apparently in other forms, the histo- 
logical structure of the inner (reticular) zone at the cortico- 
medullary border does not, in general, support the idea of a 
mechanical displacement by pressure. 
3. The remaining possibility is that there is an actual absorp- 
tion and removal of the cortex at the corticomedullary border. 
This theory is strongly supported by the available evidence. Hy- 
peremia of the inner cortical zone, absence of cell division and a 
more or less well-marked cell atrophy with degeneration and pig- 
ment formation are (as has been shown) characteristic not only 
for the rat, but for mammals in general. In most cases, this proc- 
ess of absorption is comparatively slow and inconspicuous, as in 
the rat, but in the human infant it is more prominent. The ex- 
tensive degenerative atrophy of the inner cortical zone of the 
suprarenal in the human new-born, as described by Starkel and 
Wegrzynowski (’10), Thomas C11), Kern (’11), Elliott and Ar- 
mour (’11), Landau (’13 a) and Lewis and Pappenheimer (’16), is 
therefore not a unique phenomenon, as heretofore supposed. It 
appears to be merely an exaggeration of the same fundamental 
process found in the development of the suprarenal in other 
mammals. It is thus incorrect to claim that nothing similar 
occurs in the lower animals (Kern, ’11 ; Dewitzky, ’12; Landau, 
13a). The erosion of the inner cortical zone is evidently a con- 
tinuation of the same process of degeneration and absorption of 
the cortex which removes the cortical strands at the time of the 
original confluence of the medulla. Minot (97), on the other 
hand, believed that the cells of the primitive medulla anlage dis- 
appear in the fetus, and agreed with the view of Gottschau (’83) 
that the permanent medulla is derived by transformation of the 
suprarenal cortex. 
The process of cortical erosion by the medulla may be com- 
pared with that of the absorption of the cartilage by the osteo- 
genic tissue in the zone of enchondral ossification. In both 
cases, small islands of the invaded tissue may persist for variable 
periods. It is significant that such cortical islands in the medulla 
THE AMERICAN JOURNAL OF ANATOMY, VOL. 25, No. 3 
