26 THE SUPERIOR EXTREMITY 



branches especially the second and third which arise from 

 the internal mammary in the intercostal spaces and pass 

 forwards through the pectoralis major near the margin of the 

 sternum. I 



The Lymph Vessels of the breast may be divided into two 

 sets (i) the cutaneous,, (2) the glandular. 



i. The cutaneous lymph vessels form a plexus beneath the 

 areola, and from it the vessels extend; in the fibrous septa of the 

 subcutaneous fat, towards the periphery of the breast, where 

 they join the extensive lymphatic plexus in the fascia enveloping 

 the pectoralis major the pectoral plexus. (2) The glandular 

 lymph vessels, which surround the alveoli, lie in the intra-lobular 

 connective tissue and communicate in front with the cutaneous 

 plexus and behind with the pectoral plexus. 



It is necessary to detail the various connections of the 

 pectoral plexus in order that the spread of malignant disease, 

 both by centrifugal permeation and by embolic processes, may 

 be understood. They can be conveniently tabulated. 



Connections of Pectoral Plexus. 



1. With subscapular lymph glands (p. 35), which drain the lateral part 



of the plexus. 



2. With pectoral lymph glands (p. 35), which drain the upper and lateral 



part of the plexus. 



3. With infra- clavicular lymph glands (p. 30), which drain the upper part 



of the plexus. 



4. With the lymph glands which lie along the internal mammary vessels 



in the upper intercostal spaces, and through them, with the anterior 

 mediastinal lymph glands, which thus drain the medial part of the 

 plexus. 



5. With the pectoral and cutaneous plexus of the opposite side, across the 



front of the sternum. 



6. With the sub-peritoneal plexus on the under surface of the diaphragm, 



by communications which cross the costal margin, draining the 

 lower part of the plexus. 



Mammary Abscess. Superficial abscess formation (pre- 

 mammary abscess) is caused by organismal infection of the 

 cutaneous lymph vessels or of the glands which form 

 Montgomery's tubercles. 



If the glandular lymph vessels become involved by a spreading 

 infection, the abscess forms in the substance of the breast 

 (intra-mammary abscess). In this case the abscess ramifies 

 throughout the mamma, giving rise to loculi, which may be 

 traversed by fibrous septa. 



