MUSCLES OF THE HEAD AND NECK. 173 



organs of generation. At the commencement of the alimentary canal in 

 the oesophagus, and near its termination in the rectum, the muscular coat 

 is formed by a blending of the fibres of both classes. The heart is deve- 

 loped from die middle, or vascular layer of the germinal membrane ; and 

 although involuntary in its action, is composed of ultimate fibres, having 

 the transverse striae of the muscle of animal life. 



The muscles may be arranged in conformity with the general division 

 of the body into, 1. Those of the head and neck. 2. Those of the 

 trunk. 3. Those of the upper extremity. 4. Those of the lower ex- 

 tremity. 



MUSCLES OF THE HEAD AND NECK. 



The muscles of the head and neck admit of a subdivision into those of 

 the head and face, and those of the neck. 



Muscles of the Head and Face. These muscles may be divided into 

 groups, corresponding with the natural regions of the head and face ; the 

 groups are eight in number, viz. 



1. Cranial group. 5. Superior labial group. 



2. Orbital group. 6. Inferior labial group. 



3. Ocular group. 7. Maxillary group. 



4. Nasal group. 8. Auricular group. 



The muscles of each of these groups may be thus arranged 



1. Cranial group. Levator labii superioris proprius, 

 Occipito-frontalis. Levator anguli oris, 



Zvgomaticus major, 



2. Orbital group. Zygomaticus minor, 

 Orbicularis palpebrarum, Depressor labii superioris alsequ* 

 Corrugator supercilii, nasi. 



Tensor tarsi. 



6. Inferior labial group. 



3. Ocular group. . 



(Orbicularis oris) * 



Levator palpebrae, Depressor labii inferioris, 



Rectus superior, Depressor anguli oris, 



Levator labii bferioris. 

 Kectus internus, 



Rectus externus, 7. Maxillary group. 



Obliquus superior, M 



Obliquus inferior. ^ las :er ' 



Temporalis, 



4. Nasal group. Buccinator, 

 Pyramidalis nasi, Pterygoideus externus, 

 Compressor nasi, Pterygoideus internus. 



Dilatator naris. 0/1-7 



o. Jluncular group. 



5. Superior labial group. Attollens aurem, 

 (Orbicularis oris), ^ Attrahens aurem, 

 Levator labii superioris alaeque nasi, Retrahens aurem. 



* The Orbicularis oris, from encircling the mouth, belongs necessarily to both the 

 superior and inferior labial regions; it is therefore enclosed within parentheses in 



