THE ADRENAL BODIES 563 
THE ADRENAL BODIES 
The adrenal bodies or glands (Glandule adrenales)! are two small, flattened 
organs, which lie in contact with the anterior part of the medial border of the 
kidneys #¥igs. 496, 497). They are ductless. In the horse they are red-brown in 
color, about three and a half to four inches (ca. 9 to 10 cm.) long, one to one and a 
half inches (ca. 3 to 4 em.) wide, and about half an inch or more (ea. 1.5 em.) in 
thickness. The weight varies from one to two ounces (ca. 28 to 56 gm.). 
The right adrenal body is related medially to the posterior vena cava, to which 
it is adherent. Its anterior part curves dorsally around the medial border of the 
right kidney. Its posterior part is flattened and is related ventrally to the pancreas 
and cecum, dorsally to the right renal vessels. The anterior extremity is con- 
cealed in the renal impression of the liver; the posterior is related to the ureter. 
The left adrenal body is a little shorter than the right one, and its extremities 
are rounded; it is usually curved, so that its medial border partly embraces the 
anterior mesenteric artery. Its dorsal surface is related 
to the kidney, the renal artery, the aorta, and the left 
cceliaco-mesenteric ganglion. The ventral surface is in 
relation with the left extremity of the pancreas and the 
root of the great mesentery. The posterior extremity 
often curves inward behind the anterior mesenteric 
artery; it is related behind to the left renal vein. 
When hardened in situ the adrenals present several features 
not evident in the soft organs. The anterior part of the right 
adrenal is twisted dorso-laterally over the medial margin of the 
kidney, so that this part is prismatic and has three surfaces; of 
these, the concave lateral one is applied to the kidney, the dorsal 
one is related to the right crus of the diaphragm and the liver, 
and the medial one is in contact with the posterior vena cava. 
The anterior mesenteric artery is nearly always more or less en- 
larged as a result of verminous arteritis, and the form and degree 
of curvature of the left adrenal seem to vary in conformity with 
the condition of the artery. 
Structure.—The fibrous capsule adheresintimately ,,, 5 - 
5 z - 503.—ApRENAL Bopy oF 
to the surface of the organ. It contains elastic fibers, Horse; Horrzontan Sec 
and in its deep part unstriped muscle-fibers. From it SHON WEDUCED: 
trabeculze pass radially into the substance, blending eR oLS i eerpcn cones 
% Aee 55 substance; 3, medullary substance; 
with the fine supporting reticulum. The parenchyma = { jjlood-vessel in section. (From 
consists of a cortical and a medullary part. The cor-  Leisering’s Atlas, reduced.) 
tical substance (Substantia corticalis) is red-brown in 
color, and is clearly distinguishable from the yellow medullary substance (Substantia 
medullaris). A large central vein (Vena centralis) is visible on cross-sections. 
The cells of the cortex are arranged in chains of one or two rows. In the peripheral portion 
the cells are of high cylindrical shape, and the chains form connecting loops; Giinther has pro- 
posed the name zona arcuata for this part, instead of the usual term zona glomerularis. More 
deeply the chains are distinctly palisade-like, and this region is called the zona fasciculata. Next 
to the medulla is the zona reticularis, in which the chains form a network. The cells in these two 
zones are polygonal and contain a brown pigment. The cells of the medulla are arranged in 
irregular groups or form sheaths around the veins. They react to chromic salts by assuming a 
yellow or yellow-brown color, and are termed chromaffin cells; they share this peculiarity with 
certain cells of the sympathetic ganglia and paraganglia, with which they are probably related 
genetically. The alkaloid adrenalin appears to be formed in the medullary cells. 
Vessels and Nerves.—The adrenals receive a relatively large blood-supply 
through the adrenal arteries, which arise from the renal arteries or from the aorta 
directly. The veins terminate in the posterior vena cava and the left renal vein. 
1From the standpoint of comparative anatomy the term ‘‘adrenal” is decidedly preferable 
to “suprarenal.”’ 
