Chap. 22.] [ ' *33 3 



CHAP. XXII. 



THE PLEURA, THE LUNGS, AND THE THYMUS. 



Defcription of the Tborax.-~-Tbe Pleura The Brea/ls. Breafts of 

 Infants fontain Milk. The Mediajlinum. The Lungs, The 

 Thymus. 



TH E thorax is that part of the body which lies 

 between the neck and the diaphragm. It is fur- 

 rounded by the fpine, the ribs, the flernum, and the 

 diaphragm, and alfo, internally, by a thin membrane 

 like the peritoneum, which forms two feparate cavi- 

 ties, and is called the pleura. On the external part 

 of the thorax are placed the mammas or breads ; within 

 is the heart, with its large verTels, and the lungs. 



The mammre, or breads, in men, and children of 

 both fexes, are no more than cutaneous tubercles, with 

 a brownifh circle in the middle, called the areola. In 

 women they are two convex firm bodies, of a glandu- 

 lar nature. In the middle of each bread is a promi- 

 nent fpongy fubdance, called the papilla, perforated by 

 a number of ducts for thedifcharge of the milk, around 

 which is placed the areola. The internal part of the 

 bread chiefly confids of a large quantity of fat; but 

 there is alfo a large glandular fubdance, compofed of 

 many .fmaller glands, connected together by cellular 

 membrane ; this is the organ which fecretes the milk, 

 a.nci to which the term mamma is more ftrictly appli- 

 cable. It is remarkable, that a fmall quantity of milk 

 may in general be preiled from the breads of new-born, 

 infants, both male and female. 



The pleura, as has been intimated, is a tranfparent 

 and dcnfe membrane^ continued through |he left per- 

 foration 



