At the base of the nipple, under the areola (Fig. 56), they dilate to form the lacteal sinus, then enter the nipple, and cross it entirely, opening into the grooves which separate the papillae. Their walls inclose muscu lar fibres. The acini have a cuboid epithelium; the galactophorous ducts near the nipple, have, according to de Sinety, a cylindrical epithelium. Whatever Paul Dubois may have thought of them, these galactophorous ducts do not inosculate, but enter the nipple separately.
The arteries come from the external and internal mammary and from the intercostals.
The veins go into the internal mammary and axillary. Of these veins, a certain number are sub-cutaneous and at times form, under the areola, an incomplete circle, called Haller's circle.
The nerves come from the thoracic branches of the brachial plexus and from the intercostal nerves.
The lymphatics spring from the gland and the skin; the glandular go to the axillary ganglia, those of the skin enter the sub-areolar plexus. Ac cording to Cadiat the breast of a nullipara is formed of a hard mass, com mencing at the nipple, and stretching circularly below the derma so as to form a thick plate, resting on the fatty tissue which separates it from the aponeurosis of the pectorftlis major. It is formed of fibrous tissue crossed by fine ducts, the first features of the glandular elements, which develop in consequence. Primitively, in the embryonic period, this layer
is a mass of nuclei, lenticular in form, placed below the derma.
According to Langer, in the centre of this lenticular body is a little fossa, which is the centre around which the canals of the gland, or rather the epithelial cylinders that they represent, will develops. From the time of puberty, the two parts which form the breast, namely the fibrous layer and the galactophorous ducts, develop simultaneously, but these last are only an insignificant part of the organ, in a well-formed breast. In a young girl there are no true glandular elements, only sim ple epithelial buds forming full cylinders as in the foetus.
In a pregnant woman the breast undergoes great changes. The glan dular proportion exceeds that of fibrous tissue; the ducts are not yet permeable, but at the centre is already noticeable a certain quantity of fatty particles. It is only in pregnancy that the glandular structure is completed.
After pregnancy, it is the fibrous nuclei which take the place which tho glandular resides occupy during lactation.
After the menopause retraction is still more rapid. The fibrous layer contracts little by little, and, in its place, are only found fatty deposits crossed by the larger galactophorous canals, which still remain, and which contain a greenish yellow serosity.