1072 URINARY AXD REPRODUCTIVE ORGANS 



The veins terminate in the corresponding trunks. The superficial veins become 

 visibly enlarged during ])regnancy and lactation. 



The lymphatics, originating in the cellular interspaces of the gland, form 

 trunks which accomi)any the veins; the majority terminating in the costal group 

 of axillary glands, the others in the retrosternal chain. The integument of the 

 nipple and areola, as well as the rest of the skin over the mamma, is richly supplied 

 Avith lymphatics, and as these connnunicate freely with the vessels of the other 

 side across the middle line, infection may be conveyed to the glands of the side 

 opposite to the primary seat of disease (Volkmann). In cancer of the breast the 

 deep cervical glands about the subclavian vessels may become implicated by exten- 

 sion from the axilla as the disease advances. 



The nerves are derived from the supraclavicular branches of the cervical plexus, 

 and from the intercostals. The glandular twigs are traced by Eckhard 'to the 

 fourth, iifth, and sixth intercostals. 



Development. — The breast appears about the seventh week of foetal life as a circular epider- ■ 



mic riJge, enclosing a central depression, the cells of which grow inwards and form branching ■ 



tubular ducts that radiate beneath the nipple (fig. 658). * 



Abnormalities. — Small supplementary lacteal glands, in addition to the normal accessory 

 structures beneath the areola, are frequently present around the margin of the principal gland, 

 and may be found in front of the sternum, in the axilla, and below the clavicle, and there is reason 

 to believe that many of the adenomata and cancers take origin in these redundant structures 

 (Roger Williams). Besides these, large supernumerary mammre, having all the characters of the 

 typical organs, have also been met with in various situations — in the axilla, over the back, the 

 abdomen, and even on the thigh. These are in all probability atavistic. Absence of the mamma 

 is extremely rare. 



The nipples may be double, or even triple on each breast, or may be wanting altogether. 



In a few instances an abnormal development of the gland tissue has been known to occur in 

 the male, and milk has been secreted in suificient quantity to nourish an infant. A slight and 

 temporary enlargement of the gland about the period of puberty is not infrequent. 



