404 HISTOLOGY 



In old persons all the end pieces and lobules have gone and only the 

 ducts remain. 



The ducts are lined with simple columnar epithelium, surrounded by a 

 basement membrane and generally by circular connective tissue bundles. 

 Toward the nipple each duct forms a considerable spindle-shaped dilata- 

 tion, the sinus lactiferus. The epithelium near the outlet of the ducts 

 is stratified and squamous. 



The skin of the nipple, and of the areola at its base, contains abundant 

 pigment in the deepest layers of its epidermis. The corium forms tall 

 papillae and contains smooth muscle fibers, some of which extend vertically 

 through the nipple and others are circularly arranged around the ducts. 

 There are tactile corpuscles in the nipple, and lamellar corpuscles have been 

 found beneath its areola. It is particularly sensitive, and upon irritation 

 becomes rapidly elevated, due both to muscular and vascular activity. 

 There are many sweat and sebaceous glands in the areola, and occasional 

 rudimentary hairs. The areolar glands (of Montgomery) are branched 

 tubular glands having a lactiferous sinus and otherwise resembling the 

 constituent mammary glands. Their funnel-shaped outlets are surroun ded 

 by large sebaceous glands. The areolar glands are regarded as transitions 

 between sweat glands and mammary glands. 



Blood vessels enter the breast from several sources and form capillaries 

 around the alveoli. Lymphatic vessels are found in the areola, around 

 the sinuses, and in the interlobular tissue. The collecting lymphatics pass 

 chiefly toward the axilla; a few penetrate the intercostal spaces toward 

 the sternum. The nerves are mostly those which supply the blood vessels, 

 but fibers are said to extend to the glandular epithelium. 



SUPRARENAL GLANDS. 



Development and General Features. The suprarenal glands are two 

 flattened masses of cells, without lumen or ducts, situated in the retroperi- 

 toneal tissue above the kidneys. They vary considerably in size and 

 shape, but are usually about a quarter of an inch thick and between i and 

 2 inches tall, sometimes being wider and sometimes narrower than their 

 height. The right suprarenal gland is generally described as triangular 

 and the left as crescentic. 



The gland resting upon the kidney (Glandtda Rent incumbens) was first described 

 by Eustachius (Tractatio de Renibus, 1564). It was apparent from the outset that 

 the relation of the suprarenal glands to the kidneys was merely that of juxtaposition, 

 nevertheless most anatomists still find it convenient to describe them with the urinary 

 organs. Certain early writers supposed that they were renal structures and named 

 them "succenturiate kidneys." Bartholin (Anatomia, 1666) perceived the medulla, 

 which he described as a cavity containing a black humor; and he published an extraor- 

 dinary figure in which the gland resembles a cocoanut cut across with the lid lifted. 



