THE MAMMARY GLANDS 



1301 



slightly raised area, also pigmented, the areola mammae. These two structures 

 will be described separately later. 



The dorsal surface of the mammary gland (figs. 1060, 1061) is attached and 

 concave. It is in relation in its cephalo-medial two-thirds with the fsacia over the 

 pectoralis major muscle. In its caudo-lateral third it extends over the base of 

 the axillary fossa, where it is in relation with lymphatic glands and with the ser- 

 ratus anterior muscle, and at its most caudal part, sometimes with the external 

 abdominal oblique muscle. 



The usual number of breasts in the human species is two; rarely is the number reduced, 

 much more often do we find an increase in this number. Each of these conditions is found in 

 both sexes and may be complete or partial. Complete suppression of both breasts, amastia, is 

 one of the rarest anomahes and is usually associated with other defects. Complete absence of 

 one is less rare. A more frequent condition is arrest of development, micromastia, leading to 

 rudimentary but functionless organs. Absence of the nipple, athelia, is much commoner and 

 generally affects both breasts. All grades of the imperfection from complete absence to 

 shghtly imperfect nipple may be foimd. When there is an increase this may include the whole 

 breast, polymastia, or just"^the nipple, polythelia. The supernumerary structures [mammae 



Fig. 1061. — Horizontal Section of the Right Mamma of a Woman 22 Years Old. 



(Testut. 



Pyramidal process 



Skin 

 Retinaculum cutis 



Retinaculum cutis 



Pyramidal process 

 X ,...- Skin 



Sternum '?• 



.... Superficial fascia 



Connective tissue 



Sixth rib 

 Intercostals 



accessorise] may be represented only by a pigmented area representing an areola; or by a nipple 

 with or without an areola; by a gland with a more or less perfect nipple and areola; or with 

 ducts opening without a nipple; or there may be no opening on the surface. The extra mamma 

 is very rarely perfectly developed and functional. Various observers have found the super- 

 numerary breasts or nipples occurring in from 1 to 7 per cent, of the cases examined and some- 

 what oftener in males than in females. The extra organs are found more frequently on the left 

 side, usually along a line extending from the axilla toward the genitalia. This corresponds to 

 the position in which the mammae occur in some other mammals and also to the milk line of the 

 embryo. Although they are occasionally found in other situations, over 90 per cent, of them 

 are encoimtered upon the ventral surface of the thorax along the above-mentioned line caudal 

 and medial to the normal pair of breasts. They are frequently hereditary. It is doubtful 

 whether their possessors are either more fertile or more liable to bear twins. 



The shape of the breasts varies with the development and functional activity'and the amount 

 of fat. The smooth, somewhat conical breast of the nulhpara becomes hemispherical with 

 increase in the amotmt of fat, while in emaciation it may be reduced to a flattened disc with an 

 irregular sm-face. After lactation the breasts tend to become more pendulous with marked 

 sulci between them and the thoracic walls, and after repeated pregnancies they may become elon- 

 gated so as to be almost conical or even have pedunculated bases. 



The size of the mammary gland in girls remains relatively the same as in the 

 infant up to puberty when it suddenly increases considerably and continues for a 

 time to enlarge slightly at each menstrual period. There is also a temporary 

 enlargement and soreness at each menstrual period, due perhaps to the increased 

 vascular supply. Until the age of puberty the glands measure 8 to 10 mm. in 

 diameter but when they have attained their complete adult development they 

 have increased to 100 to 110 mm. in the cephalo-medial, 120 to 130 mm. in the 

 cephalo-lateral (obhquely from above downward) direction, and 50 to 60 mra. in 

 thickness. During pregnancy the breasts again increase in size, more especially 



