226 DISSECTION OF THE UPPER LIMB. 



trunks of the nerves about midway between the spine and the sternum. 

 The other set, anterior cutaneous nerves of the thorax, are the termina- 

 tions of the same intercostal trunks at the middle line of the body. 



The anterior cutaneous nerves piercing the pectoral muscle, are directed 

 outwards in the. integuments as slender filaments. The offset of the second 

 nerve joins a cutaneous branch of the cervical plexus; and the others 

 supply the integuments and the mammary gland. Small cutaneous 

 branches of the internal mammary vessels accompany the nerves. 



The lateral cutaneous nerves (fig. 69) issue with companion vessels 

 between the digitations of the seratus muscle, and divide into an anterior 

 and a posterior piece. There is not usually any lateral cutaneous nerve 

 to the first intercostal trunk. 



The anterior offsets ( 9 ) bend over the pectoral muscle, and end in the 

 integuments and the mammary gland: they increase in size downwards, 

 and the lowest give twigs to the digitations of the external oblique muscle. 

 The cutaneous nerve of the second intercostal trunk wants commonly the 

 anterior offset. 



The posterior offsets ( 8 ) end in the integuments over the latissimus 

 dorsi muscle and the back of the scapula, and decrease in size from above 

 down. 



TLe branch of the second intercostal nerve is larger than the rest, and 

 perforates the fascia of the axilla ; it supplies the integument of the arm 

 (p. 251), and is named intercosto-humeral. As it crosses the axilla it is 

 divided into two or more pieces, and is connected to the nerve of Wris- 

 berg ( 5 ) by a filament of variable size. 



The branch of the third intercostal gives filaments likewise to the arm- 

 pit and the inner part of the arm. 



The MAMMA is the gland for the secretion of the milk, and is situate on 

 the lateral aspect of the fore part of the chest. 1 



Resting on the great pectoral muscle, it is hemispherical in form, but it 

 is rather most prominent at the inner and lower aspects. Its dimensions 

 and weight vary greatly. In a breast not enlarged by lactation, the width 

 is commonly about four inches. Longitudinally it extends from the third 

 to the sixth or seventh rib, and transversely from the side of the sternum 

 to the axilla. Its thickness is about one inch and a half. The weight of 

 the mamma ranges from six to eight ounces. 



Nearly in the centre of the gland (rather to the inner side) rises the 

 conical or cylindrical projection of the nipple or mamilla. This promi- 

 nence is about half an inch or rather more in length, is slightly turned 

 outwards, and presents in the centre a shallow depression, where it is 

 rather redder. Around the nipple is a colored ring, the areola, about 

 an inch in width, whose tint is influenced by the complexion of the body, 

 and is altered during the times of menstruation, pregnancy, and lactation. 

 The skin of the nipple and areola is provided with numerous papillae and 

 lubricating glands ; and on the surface are some small tubercles marking 

 the position of the ducts of the glands. 



In the male the mammary gland resembles that of the female in general 

 form, though it is less prominent ; and it possesses a small nipple, which 

 is surrounded by an areola provided with hairs. The glandular or secre- 

 tory structure is imperfect. 



1 If the student has a male body, he may disregard the description of the 

 mamma ; and if the body is a female, he may set aside the breast for a more con- 

 venient examination of its structure. 



