PRACTIC/iL DIRECTIONS. 441 



Cut the mylohyoid, geniohyoid, genioglossus, and the mucosa 

 of the floor of the mouth free from the mandible on both sides, so 

 that the tongue and the floor of the mouth may be drawn ventrad 

 and turned out of the way, exposing the roof of the mouth (as in 

 I'^ig. 66, p. 112). Cut through one side of the pharynx near the 

 ventral surface and turn the tongue toward the uncut side. 



The roof of the mouth is thus exposed. Dissect next — 



14. The pterygoid muscles (Fig. 66). Remove the mucosa of 

 the roof of the mouth, especially at the sides of the soft palate, and 

 the two pterygoid muscles (p. iii) are exposed. The lower jaw 

 may be removed on one side to get at their origin. 



(The muscles of the soft palate (p. 230, and Fig 66, d and e), 

 and the superior constrictor of the pharynx (p. 233, and Fig. 66,/) 

 may be observed at this point, if desired.) 



V. Muscles of the Wall of the Thorax and of the Abdomen. 



1. The scalenus (p. 141, and Fig. y^, /-/'"). To trace its 

 cervical portion, cut the trachea and oesophagus just craniad of the 

 first rib, cut the i)harynx and hyoid free from the ventral side of the 

 head and neck, and remove the pharynx, larynx, oesophagus, and 

 trachea (these should be preserved for future study of the larynx). 



2. The transversus costarum (p. 150, and Fig. 73,j). 



3. The serratus posterior superior (p. 148, and Fig. 73, /). 

 Transect this at about the middle of the muscle-bundles, and reflect 

 it in both directions. 



4. Tlie serratus posterior inferior (p. 148, and Fig. 73, n). 

 Transect and rellect as in the last. 



5. The external oblique (p. 153, and Fig. 68, p). Transect it 

 by an incision parallel to its tendon of origin and about an inch from 

 it, and reflect in both directions. 



6. The internal oblique (p. 154, and Pig. 73, o). Transect and 

 reflect as above. 



7. The transversus (p. 155, and Fig. 69, /). Requires no 

 further dissection. 



8. The rectus abdominis (p. 155, and Fig. 73, /'). Oi)en its 

 sheath by a longitudinal incision near the linea alba. 



9. The external intercostals (p. 150, and Fig. 73, m; Fig. 69, i). 

 To see these, remove the origins of the levator scapulae and serratus 

 anterior; also the serratus posterior superior. 



10. The internal intercostals (p. 151, and Fig. 69, X'). To 

 uncover these, remove the external intercostals from between two or 

 three pairs of ribs. 



11. The transversus thoracis (p. 151). To see this muscle, 

 which lies on the inner surface of the thoracic wall, it is necessary to 

 cut through the ribs on one side one or two inches from the sternum, 

 and open the thorax. The muscle can then be observed directly. 



(The levatores costarum will be dissected later.) 



