SERRATI POSTICI MUSCLES. 



523 



After removing the loose areolar tissue beneath the rhomboids 

 the thin serratus posticiis superior muscle will be laid bare. The 

 serratus posticus inferior has been already displayed by the reflection 

 of the latissimus dorsi. 



The muscles of the THIRD LAYER are the two serrati muscles. Serrati are 

 They are very thin, and receive their name from their toothed 

 attachment to the ribs. 

 Their origin from the 

 spines of the vertebrae 

 is aponeurotic. 



The upper 



the smaller; 



relations. 



The SERRATUS POSTICUS 

 SUPERIOR (fig. 190, A) 



arises from the ligamen- 

 tuni n lichee, and from 

 the spinous processes of 

 the last cervical, and 

 upper t\vo or three dorsal 

 vertebrae, with the supra- 

 spinous ligament. The 

 fleshy fibres are inclined 

 downwards and outwards, 

 and are inserted by slips 

 into four ribs, from the 

 second to the fifth, exter- 

 nal to their angles. 



The muscle rests on 

 the splenius, and is 

 covered by the rhom- 

 boidei, except at its upper 

 border. 



The SERRATUS POSTI- 

 CUS INFERIOR (fig. 3, G, 

 p. 5) is wider than the 

 preceding muscle. Its 

 aponeurosis of origin is 

 inseparably united with 

 that of the latissimus 

 dorsi, and with the fascia 

 lumborum, and is con- 

 nected to the spinous 

 processes of the last two 



dorsal and upper two or three lumbar vertebrae. The fleshy fibres 

 ascend somewhat to be inserted into the last four ribs outside their insertion ; 

 angles, each successive piece extending further forwards than the 

 one below. 



This muscle lies on the mass of the erector spinae ; and with relations, 

 the upper border of its tendon the vertebral aponeurosis is 

 united. 



Action. Both serrati are inspiratory muscles. The upper one Use of 

 raises the ribs into which it is inserted ; while the lower one draws serratl - 



FIG. 190. PART OP THE THIRD AND FOURTH 

 LAYERS OF THE MUSCLES OF THE BACK. 



A. Serratus posticus superior. 



B. Splenius capitis. 

 c. Splenius colli. 



D. Continuation of the ilio-costalis. 



E. Longissiruus dorsi. 



F. Spiualis dorsi. 



origin ; 



