THE MUSCULAR SYSTEM 



273 



derivation. The evolutionary process of subdivision, fusion, migration, 

 and splitting of muscles reaches its cUmax in primates, forearm and hand 

 being especially noteworthy. 



FRONTAL- 

 M. ORBICULARIS OCULl 



NASAL- 

 ZYGOMATIC 

 AURICULO-LABIAL SUP. 

 AURICULO-LABIAL INF. 



TRIANGULAR 



A. ATELES. 



M. PLATYSMA 



SUR AURICULAR 

 OCCIPITAL 

 POST. AURICULAR 



-J- M. ANTITRAGICUS 

 ANT. AURICULAR 



FRONTAL- 



M. ORBICULARIS OCULl 

 NASAU 



M. QUADRATUS LAB 1 1 SUR 



CANINE- 



M. ORBICULARIS OR 



M. RISORIUS 



M. QUADRATUS LAB II INF 



M. MENTAL IS 



ANT. AURICULAR 



SUP AURICULAR 



OCCIPITAL 

 POST. AURICULAR 



YGOMATIC 



"^. PLATYSMA 



TR lANGULARl 



B.HOMO. 



Fig. 227. — Mimetic muscles in monkey (ateles) and man. A. Ateles (redrawn from 

 Wilder after Ruge) and B. Homo. The similarity of these muscles both in function 

 and relations attests their similar genetic derivation. 



Muscles in Man 



In the human body are nearly four hundred paired or bilaterally 

 symmetrical muscles, of which forty-seven pairs are visceral and the rest 

 skeletal. In addition to these, four unpaired muscles are recognized. 



Muscles of the Head. One of the most distinctive features of the 

 head is the presence of numerous integumentary muscles, visceral in 

 origin, inserted in the skin of the head and neck, innervated by the facial 



