PART VI. 

 OF THE THORAX. 



BEFORE the thorax is described, it will be in order to con- 

 sider the 



Mamma ; 



Or those glandular bodies situated on the anterior part of it, 

 which, in females, are destined to the secretion of milk. 



These glands lie between the skin and the pectoral muscles, 

 and are attached to the surfaces of those muscles by cellular 

 membrane. 



They are of a circular form ; and consist of a whitish firm 

 substance, divisible into small masses or lobes, which are com- 

 posed of smaller portions or lobuli. Between these glandular 

 portions, a great deal of adipose matter is so diffused, that it 

 constitutes a considerable part of the bulk of the mammae. 



The gland, however, varies greatly in thickness in the same 

 person at different periods of life. 



The mammae become much enlarged about the age of pu- 

 berty. They are also very large during pregnancy and lacta- 

 tion ; but after the period of child-bearing they diminish con- 

 siderably. They are supplied with blood by the external and 

 internal mammary arteries, the branches of which enter them 

 irregularly in several different places. 



The veins correspond with the arteries. 



From the small glandular portions that compose the mamma, 

 fine excretory tubes arise, which unite together and form the 

 great lactiferous ducts of the gland. These ducts proceed in a 

 42 



