INTERCOSTAL MUSCLES 85 



muscles) are simply strong white fibrous bands having no power to 

 contract and no elasticity. This is equally true of the aponeuroses. 



The attachments of the extremities are spoken of as the origin 

 and the insertion. The extremity which is stationary while the 

 other end moves, is the origin; the end which moves with the 

 organ attached to it, is the insertion. 

 The insertion is always pulled toward the 

 origin when the muscle contracts. 



The names of muscles are not applied 

 according to a uniform plan, being some- 

 times chosen because of location, as the 

 intercostals (between ribs) or the epicranial 

 muscle (upon the head), etc; or, the shape 

 may determine the name, as orbicularis 

 oris (ring muscle of the mouth) ; but of tenest 

 the name signifies the action of the muscle. 

 The original names are in the Latin tongue 

 but the English translation is often used. 

 The full Latin name includes the word 

 musculus (muscle) which is quite com- 

 monly omitted for the sake of brevity. 



SKELETAL MUSCLES OF THE TRUNK 1 



Intercostal muscles. In two sets, the 



internal and the external, which occupy 

 the intercostal spaces. The fibers run 



obliquely from rib to rib, the internal 



, , . FIG. 74. THE FIGURES 



fibers running upward and forward, the REFER TO THE SPINAL GROUP 



external fibers running downward * *^(&I ^5 



forward. (Fig. 73.) 



Action. They move the ribs up and down in breathing and 

 the various acts associated with it. 



PRINCIPAL MUSCLES OF THE BACK 



In the skeleton a broa^i groove exists on either side of the 

 spinous processes, which is filled in its whole extent with many 

 vertical muscles of different lengths, the use of which 'is to hold 



1 Many skeletal muscles have their origin partly from the deep fascia covering 

 them. The bony origins alone are given here, as a rule and only the more important 

 of those. 



