68 



MUSCLES. 



of those of the a3sophagLis, are striped ; that is, have their fibres 

 arranged in parallel lines ; while all other muscles, including those 

 of the alimentary canal, the uterus and the bladder, all of which 

 are involuntary, are unstriped, that is, the fibres cross each other 

 and interlace, and always form the walls of a cavity. The red 

 colour of muscles is not dependent upon the capillary vessels, but 

 upon a peculiarity of colouring matter united with them. After 

 death they become stiff, as the fibrin coagulates, which rigidity 

 is the rigor mortis. They are well supplied with vessels and 

 nerves, and can be made to contract by external irritation after 

 death, such as galvanism, &c., 



Every muscle has a belly and two extremities ; that which is 

 fixed is called the origin or heacl^ that which is movable, the in- 

 sertion. Those which have neither origin nor insertion, and sur- 

 round orifices, are called sphincters. 



A tendon is formed of condensed white fibrous tissue, reaching 

 from the end of a muscular fibre to some structure which it is in- 

 tended to move. 



MUSCLES OF THE HEAD AND NECK. 



Occipito frontalis.^ ^^ — Has four bellies. 

 Origin, from the superior semicircular ridges of the occiput. 

 Insertion, into the superior margin of the orbicularis oculi, and cor- 



rugator supercilii, and into the 

 Fig. 55. internal angular process of the 



OS frontis and os nasi. Use ; 

 elevates the eyebrows making 

 transverse wrinkles. 



Compressor Naris.^ — Origin, 

 from the root of the ala nasi. 

 Insertion, tendinously into its 

 fellow on the dorsum of the 

 nose, and into the lower part 

 of the OS nasi. Use; it either 

 compresses or dilates the 

 nostril. 



Orbicularis palpebrarum.'*' 

 — This is a sphincter surround- 

 ing the orbits of the eyelids. 

 Origin, from the nasal pro- 

 cess of the superior maxillary, 

 the OS unguis, the internal an- 

 gular process of the os frontis, 

 and tlie internal palpebral ligament. liisertioii, into the orbitar 

 and nasal processes of the superior maxillary, and into the palpebral 

 ligament. Use; it closes the eyes. 



