THYMUS, THYROID, SUPRA-RENAL CAPSULE. 51 
THE DUCTLESS GLANDS. 
THYMUS. 
What is the structure of the thymus ? 
It is covered with a dense connective-tissue coat or capsule, from 
which trabeculee run down into the cortical or outer portion of the 
gland dividing it into chambers. These chambers are filled with 
masses of lymphoid tissue called follicles. In the inner or medullary 
portion of the gland the follicles are fused together into one mass of 
lymphoid tissue. Scattered in this tissue in the medullary portion are 
found concentrically-arranged clusters of flat epithelial cells called the 
“corpuscles of Hassall.” 
THYROID. 
What is the structure of the thyroid ? 
It consists of two lobes united by a commissure, and surrounded by a 
dense connective-tissue capsule. ‘he gland is made up of a series of 
round or oval-shaped alveoli which have no excretory ducts. These 
alveoli are filled with a translucent material which may be converted 
into colloid. They are lined with a layer of cuboidal cells resting upon 
a delicate basement inembrane. These cells may become flattened from 
pressure of the contents of the alveoli. Bloodvessels ramify between 
the alveoli. 
SUPRA-RENAL CAPSULE. 
Describe the structure of a supra-renal capsule. 
The organ is enclosed in a firm connective-tissue capsule in which 
are numerous involuntary muscle cells. Fine processes or septa of 
connective tissue run down into the gland from the capsule, and, being 
joined by delicate transverse bands, divide the cortex into chambers of 
various shapes. Beneath the capsule these chambers are small and 
irregular in shape; deeper in, the chambers are long and narrow; 
while still further in, at the inner border of the cortex, they are small 
and irregular. In the medullary portion of the gland the sustaining 
structure is a delicate reticular tissue. These spaces in the supra- 
renal capsules are filled with the parenchyma cells of the organ. In 
the cortical chambers they are large, polyhedral and granular; there 
are also seen here a few small cylindrical or cuboidal cells. The cells 
in the long chambers contain fatdrops, and those in the inner zone of 
the cortex contain pigment. ‘The cells in the medullary portion of the 
gland are spheroidal, angular or branched. The bloodvessels and 
nerve fibres are numerous, 
