158 Intercoftal Mufcles. [Book IX i 



the third, fourth, and fifth ribs, and is inferted into the 

 coracoid procefs of the fcapula. Its ufe is to bring the 

 fcapula downwards and forwards, or that being fixed* 

 to pull the ribs upwards. 



The fefratus magnus originates from the nine fu- 

 perior ribs, by an equal number of flefhy points, 

 refembling the teeth of a faw, whence the term ferra- 

 tus is derived. Faffing over two angles of the 

 fcapula it is inferted into its bafe. Its effect is to move 

 the fcapula forwards, or when the fcapula is forcibly 

 raifed, to draw the ribs upwards. 



The mufcles which cover the ribs being removed* 

 we obferve the fpace between the ribs filled up with 

 double rows of mufcles, called the intercoftales externi 

 and tnterni. The external arife from the inferior acute 

 edge of each rib, and running obliquely forwards are 

 inferted into the obtufe upper furface of the rib next 

 below. The internal arife in the fame manner as the 

 external, except that, contrary to them, they begin at 

 the fternum, and run obliquely backwards. The two 

 rows of intercoftals, therefore, decuffate each other like 

 the ftrokes of the letter X. The effect of the con- 

 traction of both feries is the fame, viz. that of bringing 

 the ribs nearer to each other, and as each lower rib is 

 more moveable than that above j to raife the ribs, dilate 

 the thorax, and affift in infpiration. 



Certain portions, both of the external and internal 

 intercoftals, are longer, and paffing over one rib are in- 1 

 ferted into the next below it. The ribs are likewife 

 raifed, and their pofterior articulations ftrengthened, by 

 twelve fhort mufcles, which arife, from eleven of the 

 tranfverfe proceffes of the dorfal vertebra, and the 

 lowefl of thofe of the neck, and which are inferted intd 

 the rib immediately below the tranfverfe procefs from 

 which each of them rifes. 



Tt-efterno-coftalisarifes from the cartilago enfifor- 



mis, 



