I.] DISSECTION OF A BABBIT AND OF A DOG. 15 



4. Note the scalenus medius running from the 

 neck to the upper ribs (2nd to 5th); cut this 

 through where it is inserted into the ribs and 

 turn it forward, the scalenus anticus will be 

 seen attached to the 1st rib at its junction with 

 the costal cartilage. 



5> The serratus anticus minor running from the 

 upper part of the internal border of the scapula 

 to the lower cervical vertebra and 1st and 2nd 

 rib. 



6. The serratus posticus, a thin inconspicuous 

 muscle proceeding by rather a long broad tendon 

 from the cervical vertebrae and dorsal fascia. 

 It is inserted into the 4 — 12th ribs about the 

 middle part of their course. 



7. These muscles having been cut through the 

 small scalenus posticus will be seen running 

 from the neck to the 1st rib laterally of the 

 scalenus anticus. The three scaleni originate 

 from one or more of the transverse processes of 

 the 4th to 7th cervical vertebrae. 



8. Note the thick muscle the longissimus dorsi 

 covering the ribs dorsally ; cut away this and the 

 adjoining muscles and note the inconspicuous 

 levatores costarum proceeding from the trans- 

 verse processes of the dorsal vertebris to the ribs 

 below. 



9. Clear away all muscles and tendons attached to 

 any two of the ribs (say 4th and 5th) except the 

 intercostal muscles joining them. Note the 

 external intercostal muscle, the fibres run 



