GENERAL CONSIDERATIONS ON TEE STRIPED MUSCLES. 227 



the two square bones, to imitate the action of the elevator muscles ; we then see 

 the internal extremity of the pterygoid bone glide on the facet of the sphenoid, 

 and push before it the palatine bone, during which the zygomatic bone acts in the 

 same manner on the maxillary ; and in this way is produced, through the influence 

 of this postero-anterior propulsion, the ascending movemeijit we undertook to 

 explain. 



THIED SECTION. 



The Muscles. 



After the study of the bony levers and their articulations, comes the description 

 of the agents whose function it is to move them. These are the muscles — fibrous 

 organs possessing the property of contracting under the influence of a stimulus. 



They are distinguished as striped or striated, and smooth or non-striated 

 muscles, according to the character of the anatomical element composing them. 



The striped muscles differ from the smooth, in that, with the exception of 

 the tissue of the heart, their contractile power is immediately placed under the 

 influence of the will. They are more particularly concerned in the functions of 

 relation, which cause them to be also named the external muscles, or muscles 

 of animal life. These muscles are nearly all attached to the skeleton, and are 

 the active agents in moving the bony framework ; they will, therefore, be the 

 only ones referred to in this place, in studying the locomotory apparatus. 



The unstriped muscles are removed from the influence of the will, and belong 

 to the organs of vegetative life. They are also designated internal muscles^ 

 involuntary muscles, or muscles of orgastic life. 



But before entering upon the particular description of each muscle, we will 

 allude to the general considerations relating to their history. 



CHAPTER I. 



GENERAL CONSIDERATIONS ON THE STRIPED MUSCLES. 



THE STRIPED MUSCLES IN GENERAL. 



In this first paragraph, we will survey, in a general manner, the volume, situation, 

 form, direction, attachments, relations, and names of the muscles belonging to 

 the locomotory apparatus. 



A. Volume. — Nothing is more variable than the volume of the external 

 muscles. What a difference there is, for example, between the small scapulo- 

 humeralis muscle and the biceps femoris or longissimus dorsi, and what a 

 number of intermediate sizes between these three points of comparison ! There 

 are consequently very great, great, medium, small, and very small muscles. 



The weight of the total mass of these organs varies according to the species. 



