14 ELEMENTARY PHYSIOLOGY. [l. 



root of the spinal nerve. Observe carefully the 

 roots on the outside of the dura mater, they join 

 almost immediately forming the nerve trunk, on 

 the posterior root at or a little before its junction 

 with the anterior root note the swelling caused 

 by the spinal ganglion. 



C. 1. Examine again the diaphragm (cp. A 16). 

 Observe the large central tendon, with the vena 

 cava and oesophagus passing through and tightly 

 attached to it. The muscular part of the 

 diaphragm consists of a costal and vertebral 

 portion. The former is attached by short 

 tendons to the ribs and sternum. The latter 

 is attached to the upper lumbar vertebrae ; it is 

 a somewhat thick mass of muscle divided into 

 right and left portions by the descending aorta, 

 the right is much the larger ; the two form the 

 pillars of the diaphragm. 



Pull down the diaphragm by its pillars, on its 

 unpunctured side the lung will follow it. 



2. Observe the pectoral muscle proceeding from 

 nearly the whole length of the sternum to the 

 humerus, cut it through together with the 

 vessels and nerves going to the arm and note 

 its attachments. 



3. Several muscles will now be exposed, note the 

 serratus anticus major proceeding from the 

 lower part of the internal border of the scapula 

 to the 3rd to 9th ribs inclusive. Cut it through 

 and reflect the parts. 



