CONNECTION OF MUSCLES AND BONES. 



17 



size of the muscle, and they serve to attach the muscles 

 firmly to the bones, to which, acting like ropes, they 

 transmit the tension of the muscles. One of the two 

 bones to which a muscle is attached is usually less 

 mobile than the other, so that 

 when the muscle shortens, 

 the latter is drawn down 



.,111^'f 



against the former. In such 





§•! 



a case the point of attach- 

 ment of the muscle to the 

 less mobile bone is called its 

 origin, while the point to 

 which it is fixed on the more 

 mobile bone is called its at- 

 tachment (epiphysis). For 

 instance, there is a muscle 

 which, originating from the 

 shoulder-blade and collar- 

 bone, is attached to the 

 upper arm-bone ; when this 

 muscle is shortened, the arm 

 is raised from its perpen- 

 dicular pendant position in- 

 to a horizontal position. A 

 muscle is not always ex- 

 tended between two con- 

 tiguous bones. Occasionally 

 passing over one bone, it at- 

 taches itself to the next. This is the case with several 

 muscles which, originating from the pelvic bone, pass 

 across the upper thigh-bone, and attach themselves to 

 the lower thigh-bone. In such cases the nmscle is 

 capable of two different movements : it can either 



/.' 



Fig. 5. The double-iikaded 

 CALF :mus(;lk (M. gastiome- 



mhis), WITH ITS TWO TEN- 

 DONS. 



a, a. The two lieals. c. The com- 

 nri'^ncement of the tendon which at 

 k is attached to tlie heel-boue. 



