The different ducts of these reservoirs take a straight course, diminishing in size, through the nipple to its extremity, where they terminate in a cribriform manner, with very contracted orifices, varying in size from those of a bristle to a common pin. Their number is about twenty.
Arteries.—The mamma receives its sup ply of blood from branches of the internal mammary, axillary, and intercostal arteries. Sir Astley divides them into anterior and pos terior, the former passing from the axillary artery and the latter from the internal 'Dam mart', and there is generally a large vessel entering the pectoral or costal surface of the breast and sending its branches through the gland to meet the others upon the surface of the organ. The branches from the axillary are given off by the superior and long thoracic arteries; those from the internal mammary are either derived directly from that vessel or from its intercostal branches. " The arteries upon the cutaneous surface of the breast are lodged in the festoons formed by the ligaments sus pensoria, and proceed to the nipple. There their extreme branches pass each other at the base of the nipple. They send branches for wards from the base to the apex of the nipple, which are parallel to each other and divide into very minute branches which supply the papilla and the ducts. They also send branches from the base of the nipple backwards into the gland at its centre, and they freely anastomose with those arteries which enter the back of the gland, and they then distribute their ramifica tions to its substance." Veins.—" The branches of the veins arising from the nipple pass from its papilla in parallel branches to its base, and then form radii to an ellipse behind the areola at its margin." Their minute divisions in the papilla with the cor responding divisions of the artery constitute the erectile tissues. From the ellipsis of veins four principal branches proceed, beside others which are less important : these are distri buted on the fore part of the breast, forming a net-work by their free anastomoses.
They terminate, 1st, by two large branches in the axillary vein, and by several branches in the vein accompanying the arteria thoracica longa; 2d, in the cephalic ; 3d, in the internal mammary vein by branches which pass between either the first and second or the second and third ribs; 4th, by a deep-seated vein which enters the fourth mammary intercostal vein ; 5th, a plexus of veins passes over the clavicle to terminate in the external jugular and sub clavian veins.
Nerves.—These are derived from the dorsal division of the spinal cord. The third dorsal nerve descends upon the vessels which are distri buted to the nipple and gland, the fourth and fifth are distributed directly to the breast, and the sixth sends some filaments upon the extre mities of those arteries which have passed the nipple, but which send branches into the gland. It also receives a supply from the grand sym pathetic nerve.
Absorbenls.—These vessels are described by Sir Astley Cooper as follows :— " These vessels always exist in great numbers in the breast, and when the gland is in a state of lactation they are readily injected and demonstrated.
" They are divided into a superficial and deep-seated order. The first are cutaneous and are most connected with the nipple and the mucous glands of the skin, and the second arise from the interior of the glandular and secretory structure of the mamma.
" The superficial arise from the nipple, and they pass principally upon the surface of the gland, behind the skin, oyits axillary side.
" In my injections I find them as follows:— " First, they pass upon and then under the superficial fascia, and between it and the aponeurosis of the pectoral muscle. They are next continued over the intercostal muscles.
" Here they enter the absorbent or cribriform opening, or sometimes there are two openings in the fascia axilla, as it there passes from the edge of the pectoralis major to that of the teres major and latissimus dorsi muscles, and which fascia shuts up and forms the floor of the axilla.
" Having passed through this fascia into the axilla they enter the first set of axillary absorb ent glands, and form a considerable plexus of absorbent vessels between them.