48 LABORATORY MANUAL OF HUMAN ANATOMY 



should be taken to avoid giving a " ragged " appearance to the 

 surface of the muscle. As soon as the trunk of a nerve or blood- 

 vessel is found, ascertain its name from a study of the illustra- 

 tion in your atlas. Look up this name in the index to your Sys- 

 tematic Human Anatomy and refer to the author's description. 

 When handling a nerve, blood-vessel, or indeed any structure, 

 form the habit of repeating to yourself its name ; this practice 

 is extremely helpful in fixing the association between the struct- 

 ure and the name which is the sign for it. Also, when reading 

 write down every new term met with and learn its meaning, both 

 literal or etymological and applied or derived. 



Nerves. (Fig. 4.) 



(a) Cutaneous branches of posterior rami of thoracic nerves (rami 



cutanei Rr. post. Nn. thoracalium). 



(b) Posterior rami of lateral cutaneous rami of anterior rami of inter- 



costal nerves (rami posteriores Rr. cutan. lat. Rr. ant. Nn. inter- 

 costalium). 



(c) Medial rami of posterior rami of lumbar, sacral, and coccygeal 



nerves (rami mediales Rr. post. Nn. lumb., sacral., et coccyg.}. 



(d) Lateral rami of posterior rami of lumbar nerves (rami laterales 



Rr. post. Nn. lumbalium = Nn. clunium superiores). 

 Arteries. 



(a) Medial cutaneous rami of posterior rami of intercostal arteries 



(rami cutanei mediales Rr. post. Aa. intercostalium) . 



(b) Lateral cutaneous rami of posterior rami of intercostal arteries 



(rami cutanei laterales Rr. post. Aa. intercostalium). 



(c) Dorsal cutaneous rami of lumbar arteries (rami cutanei dorsales 



Aa. lumbalium). 



(d) Posterior rami of lateral cutaneous rami of anterior rami of inter- 



costal arteries (rami posteriores Rr. cutan. lat. Rr. ant. Aa. 

 intercostalium) . 

 Veins. (Cf. Toldt, Fig. 1036.) 



(a) Dorsal rami of intercostal veins (rami dorsales Vv. intercostalium). 



(b) Branches of lumbar veins (Vv. lumbales). 



Broad Muscles of the Back (First Layer). (Fig. 5.) 



(a) Trapezius muscle (M. trapezius}. 



(b) Broadest muscle of back (M. latissimus dorsi). 



Study the form and position of each, and establish its exact 

 origin and insertion. Test the action of the fibres of the different 

 parts of the muscles. Find their innervation now or later. To 

 what other structures are these muscles related! Examine the 

 boundaries and floor of the " triangle of auscultation." Why 

 is it so called! Examine the boundaries and floor of Petit 's 

 triangle (trigonum lumbale [Petiti]). 



