114 SURGICAL ANATOMY OF 



cisions should, if possible, be made parallel to the course 

 of the galactiferous ducts, if near the nipple, in order to 

 avoid cutting across them. Guided by the fascial en- 

 velope, collections of matter connected with the mam- 

 mary gland will occasionally point, and require opening 

 at the anterior border of the axilla. 



The diaphragmatic region, or floor of thorax, is formed 

 by the diaphragm, which constitutes the septum between 

 the thoracic and abdominal viscera, and is the muscle 

 of normal respiration. Its height, or the amount of 

 encroachment upon the thorax during ordinary respi- 

 ration, depends in some measure upon the amount of 

 distension and the size of those abdominal viscera in 

 immediate relation with it viz., the stomach, intes- 

 tines, and the liver. During normal expiration the 

 right arch ascends to the level of the fifth rib. Forced 

 expiration brings the right arch of the muscle that 

 above the liver to a level with the fourth costal car- 

 tilage in front, with the fifth, sixth, and seventh ribs 

 at the side, and with the eighth rib behind. The 

 left arch is lower than the right by two ribs. During 

 forced inspiration the muscle descends to the level of a 

 line extending from the ensiform cartilage to the tenth 

 rib. 



The under surface of the diaphragm is perforated by 

 three large foramina: (1) The aortic, situate between 

 the pillars of the muscle and spinal column, transmits 

 the aorta, the thoracic duct, and the vena azygos major. 

 (2) The caval, quadrilateral in shape and incapable of 

 constriction, transmits the inferior vena cava. (3) The 

 oasophageal, elliptiform in shape and capable of con- 

 striction, transmits the oesophagus, also the vagi nerves, 



